diff --git a/headers/private/drivers/scsi_cmds.h b/headers/private/drivers/scsi_cmds.h
index 7d3a1e2164..160ce884d8 100644
--- a/headers/private/drivers/scsi_cmds.h
+++ b/headers/private/drivers/scsi_cmds.h
@@ -255,7 +255,10 @@ typedef struct scsi_res_inquiry {
 										// Asynchronous Event Notification Capable
 	);
 	uint8	additional_length;			// total (whished) length = this + 4
-	uint8	_res5;
+	B_LBITFIELD8_2(
+		protect : 1,
+		_res5_1 : 7
+	);
 	uint8	_res6;
 	B_LBITFIELD8_8(
 		soft_reset : 1,					// 0 = soft reset leads to hard reset
@@ -350,7 +353,7 @@ typedef struct scsi_page_block_limits {
 	);
 	uint8	page_code;
 
-	uint16	_page_length;
+	uint16	page_length;
 	B_LBITFIELD8_2(
 		wsnz : 1,
 		_res4_1 : 7
@@ -424,13 +427,36 @@ typedef struct scsi_cmd_read_capacity_long {
 	uint8	service_action;
 	uint64	lba;
 	uint32	alloc_length;
-	uint8	relative_address;
+	B_LBITFIELD8_2(
+		pmi : 1,
+		_res14_1 : 7
+	);
 	uint8	control;
 } _PACKED scsi_cmd_read_capacity_long;
 
 typedef struct scsi_res_read_capacity_long {
 	uint64	lba;					// big endian
 	uint32	block_size;				// in bytes
+	B_LBITFIELD8_4(
+		prot_en : 1,
+		p_type : 3,
+		rc_basis : 2,
+		_res12_6 : 2
+	);
+	B_LBITFIELD8_2(
+		logical_blocks_per_physical_block_exponent : 4,
+		p_i_exponent : 4
+	);
+	B_LBITFIELD8_3(
+		lowest_aligned_lba_p1 : 6,
+			// first part of the Lowest Aligned LBA field
+		lbprz : 1,
+		lbpme : 1
+	);
+	uint8	lowest_aligned_lba_p2;
+		// second part of the Lowest Aligned LBA field
+		// (B_LBITFIELD16_3 would not help here because of its alignment)
+	uint8	_res16[16];
 } _PACKED scsi_res_read_capacity_long;
 
 
@@ -508,16 +534,38 @@ typedef struct scsi_cmd_rw_16 {
 } _PACKED scsi_cmd_rw_16;
 
 
+// WRITE SAME (10)
+
+typedef struct scsi_cmd_wsame_10 {
+	uint8	opcode;
+	B_LBITFIELD8_6(
+		_obsolete1_0 : 1,
+		_obsolete1_1 : 1,
+		_obsolete1_2 : 1,
+		unmap : 1,
+		anchor : 1,
+		write_protect : 3
+	);
+	uint32	lba;
+	B_LBITFIELD8_2(
+		group_number : 5,
+		_res6_5 : 3
+	);
+	uint16	length;
+	uint8	control;
+} _PACKED scsi_cmd_wsame_10;
+
+
 // WRITE SAME (16)
 
 typedef struct scsi_cmd_wsame_16 {
 	uint8	opcode;
 	B_LBITFIELD8_6(
-		_res1_0 : 1,
+		ndob : 1,
 		lb_data : 1,
 		pb_data : 1,
 		unmap : 1,
-		_res1_4 : 1,
+		anchor : 1,
 		write_protect : 3
 	);
 	uint64	lba;
diff --git a/headers/private/drivers/scsi_periph.h b/headers/private/drivers/scsi_periph.h
index 9d470c6c1a..a6e78f2a37 100644
--- a/headers/private/drivers/scsi_periph.h
+++ b/headers/private/drivers/scsi_periph.h
@@ -73,7 +73,8 @@ typedef struct scsi_periph_callbacks {
 } scsi_periph_callbacks;
 
 typedef struct scsi_block_range {
-	uint64	offset;
+	// values are in blocks
+	uint64	lba;
 	uint64	size;
 } scsi_block_range;
 
@@ -123,7 +124,7 @@ typedef struct scsi_periph_interface {
 	err_res (*synchronize_cache)(scsi_periph_device device, scsi_ccb *request);
 
 	status_t (*trim_device)(scsi_periph_device_info *device, scsi_ccb *request,
-		scsi_block_range* ranges, uint32 rangeCount);
+		scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks);
 
 	// *** removable media ***
 	// to be called when a medium change is detected to block subsequent commands
diff --git a/src/add-ons/kernel/bus_managers/ata/ATADevice.cpp b/src/add-ons/kernel/bus_managers/ata/ATADevice.cpp
index 41f633da5a..d8d19f77a5 100644
--- a/src/add-ons/kernel/bus_managers/ata/ATADevice.cpp
+++ b/src/add-ons/kernel/bus_managers/ata/ATADevice.cpp
@@ -177,6 +177,8 @@ ATADevice::ReadCapacity(ATARequest *request)
 	}
 
 	scsi_res_read_capacity data;
+	memset(&data, 0, sizeof(data));
+
 	data.block_size = B_HOST_TO_BENDIAN_INT32(fBlockSize);
 
 	if (fTotalSectors <= UINT_MAX) {
@@ -184,7 +186,8 @@ ATADevice::ReadCapacity(ATARequest *request)
 		data.lba = B_HOST_TO_BENDIAN_INT32(lastBlock);
 	} else
 		data.lba = UINT_MAX;
-	TRACE("returning last block: %lu\n", B_BENDIAN_TO_HOST_INT32(data.lba));
+	TRACE("returning last block: %" B_PRIu32 "\n",
+		B_BENDIAN_TO_HOST_INT32(data.lba));
 
 	copy_sg_data(ccb, 0, ccb->data_length, &data, sizeof(data), false);
 	ccb->data_resid = MAX(ccb->data_length - sizeof(data), 0);
@@ -198,15 +201,29 @@ ATADevice::ReadCapacity16(ATARequest *request)
 	TRACE_FUNCTION("%p\n", request);
 
 	scsi_ccb *ccb = request->CCB();
+	scsi_cmd_read_capacity_long *command
+		= (scsi_cmd_read_capacity_long *)ccb->cdb;
+	if (command->pmi || command->lba) {
+		request->SetSense(SCSIS_KEY_ILLEGAL_REQUEST, SCSIS_ASC_INV_CDB_FIELD);
+		return B_ERROR;
+	}
+
+	uint32 allocationLength = B_BENDIAN_TO_HOST_INT32(command->alloc_length);
+
 	scsi_res_read_capacity_long data;
+	memset(&data, 0, sizeof(data));
+
 	data.block_size = B_HOST_TO_BENDIAN_INT32(fBlockSize);
 
 	uint64 lastBlock = fTotalSectors - 1;
 	data.lba = B_HOST_TO_BENDIAN_INT64(lastBlock);
-	TRACE("returning last block: %llu\n", data.lba);
+	TRACE("returning last block: %" B_PRIu64 "\n",
+		B_BENDIAN_TO_HOST_INT64(data.lba));
 
-	copy_sg_data(ccb, 0, ccb->data_length, &data, sizeof(data), false);
-	ccb->data_resid = MAX(ccb->data_length - sizeof(data), 0);
+	size_t copySize = min_c(allocationLength, sizeof(data));
+
+	copy_sg_data(ccb, 0, ccb->data_length, &data, copySize, false);
+	ccb->data_resid = MAX(ccb->data_length - copySize, 0);
 	return B_OK;
 }
 
diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h b/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
index b016dab232..d222281ce1 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
@@ -334,7 +334,7 @@ extern pci_x86_module_info* gPCIx86Module;
 
 #define LO32(val) ((uint32)(addr_t)(val))
 #define HI32(val) ((uint32)(((uint64)(addr_t)(val)) >> 32))
-#define ASSERT(expr) if (expr) {} else panic(#expr)
+#define ASSERT(expr) if (expr) {} else panic("%s", #expr)
 
 #define PCI_VENDOR_INTEL	0x8086
 #define PCI_VENDOR_JMICRON	0x197b
diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
index bf5f662b7d..29841b52e6 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 Haiku, Inc. All rights reserved.
+ * Copyright 2008-2021 Haiku, Inc. All rights reserved.
  * Copyright 2007-2009, Marcus Overhagen. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
@@ -7,6 +7,7 @@
  *		Axel Dörfler, axeld@pinc-software.de
  *		Michael Lotz, mmlr@mlotz.ch
  *		Alexander von Gluck IV, kallisti5@unixzen.com
+ *		David Sebek, dasebek@gmail.com
  */
 
 
@@ -47,6 +48,18 @@
 #define INQUIRY_BASE_LENGTH 36
 
 
+// DATA SET MANAGEMENT command limits
+
+#define DSM_MAX_COUNT_48			UINT16_MAX
+	// max number of 512-byte blocks (48-bit command)
+#define DSM_MAX_COUNT_28			UINT8_MAX
+	// max number of 512-byte blocks (28-bit command)
+#define DSM_RANGE_BLOCK_ENTRIES		64
+	// max entries in a 512-byte block (512 / 8)
+#define DSM_MAX_RANGE_VALUE			UINT16_C(0xffff)
+#define DSM_MAX_LBA_VALUE			UINT64_C(0xffffffffffff)
+
+
 AHCIPort::AHCIPort(AHCIController* controller, int index)
 	:
 	fController(controller),
@@ -64,7 +77,9 @@ AHCIPort::AHCIPort(AHCIController* controller, int index)
 	fTestUnitReadyActive(false),
 	fPortReset(false),
 	fError(false),
-	fTrimSupported(false)
+	fTrimSupported(false),
+	fTrimReturnsZeros(false),
+	fMaxTrimRangeBlocks(0)
 {
 	B_INITIALIZE_SPINLOCK(&fSpinlock);
 	fRequestSem = create_sem(1, "ahci request");
@@ -585,26 +600,69 @@ AHCIPort::ScsiVPDInquiry(scsi_ccb* request, ata_device_infoblock* ataData)
 	switch (cmd->page_code) {
 		case SCSI_PAGE_SUPPORTED_VPD:
 		{
-			scsi_page_list vpdPageData;
-			vpdDataLength = sizeof(vpdPageData);
+			// supported pages should be in ascending numerical order
+			const uint8 supportedPages[] = {
+				SCSI_PAGE_SUPPORTED_VPD,
+				SCSI_PAGE_BLOCK_LIMITS,
+				SCSI_PAGE_LB_PROVISIONING
+			};
 
-			vpdPageData.page_code = cmd->page_code;
+			const size_t bufferLength = sizeof(scsi_page_list)
+				+ sizeof(supportedPages) - 1;
+			uint8 buffer[bufferLength];
+
+			scsi_page_list* vpdPageData = (scsi_page_list*)buffer;
+			memset(vpdPageData, 0, bufferLength);
+
+			vpdPageData->page_code = cmd->page_code;
 			// Our supported pages
-			vpdPageData.page_length = 1;
-			vpdPageData.pages[0] = SCSI_PAGE_BLOCK_LIMITS;
+			vpdPageData->page_length = sizeof(supportedPages);
+			memcpy(vpdPageData->pages, supportedPages, sizeof(supportedPages));
+
+			uint8 allocationLength = cmd->allocation_length;
+			vpdDataLength = min_c(allocationLength, bufferLength);
 
 			transactionResult = sg_memcpy(request->sg_list, request->sg_count,
-				&vpdPageData, vpdDataLength);
+				vpdPageData, vpdDataLength);
 			break;
 		}
 		case SCSI_PAGE_BLOCK_LIMITS:
 		{
 			scsi_page_block_limits vpdPageData;
-			vpdDataLength = sizeof(vpdPageData);
+			memset(&vpdPageData, 0, sizeof(vpdPageData));
 
 			vpdPageData.page_code = cmd->page_code;
-			vpdPageData.max_unmap_lba_count
-				= ataData->max_data_set_management_lba_range_blocks;
+			vpdPageData.page_length
+				= B_HOST_TO_BENDIAN_INT16(sizeof(vpdPageData) - 4);
+			if (fTrimSupported) {
+				// We can handle anything as long as we have enough memory
+				// (UNMAP structure can realistically be max. 65528 bytes)
+				vpdPageData.max_unmap_lba_count
+					= B_HOST_TO_BENDIAN_INT32(UINT32_MAX);
+				vpdPageData.max_unmap_blk_count
+					= B_HOST_TO_BENDIAN_INT32(UINT32_MAX);
+			}
+
+			uint8 allocationLength = cmd->allocation_length;
+			vpdDataLength = min_c(allocationLength, sizeof(vpdPageData));
+
+			transactionResult = sg_memcpy(request->sg_list, request->sg_count,
+				&vpdPageData, vpdDataLength);
+			break;
+		}
+		case SCSI_PAGE_LB_PROVISIONING:
+		{
+			scsi_page_lb_provisioning vpdPageData;
+			memset(&vpdPageData, 0, sizeof(vpdPageData));
+
+			vpdPageData.page_code = cmd->page_code;
+			vpdPageData.page_length
+				= B_HOST_TO_BENDIAN_INT16(sizeof(vpdPageData) - 4);
+			vpdPageData.lbpu = fTrimSupported;
+			vpdPageData.lbprz = fTrimReturnsZeros;
+
+			uint8 allocationLength = cmd->allocation_length;
+			vpdDataLength = min_c(allocationLength, sizeof(vpdPageData));
 
 			transactionResult = sg_memcpy(request->sg_list, request->sg_count,
 				&vpdPageData, vpdDataLength);
@@ -612,7 +670,6 @@ AHCIPort::ScsiVPDInquiry(scsi_ccb* request, ata_device_infoblock* ataData)
 		}
 		case SCSI_PAGE_USN:
 		case SCSI_PAGE_BLOCK_DEVICE_CHARS:
-		case SCSI_PAGE_LB_PROVISIONING:
 		case SCSI_PAGE_REFERRALS:
 			ERROR("VPD AHCI page %d not yet implemented!\n",
 				cmd->page_code);
@@ -669,6 +726,8 @@ AHCIPort::ScsiInquiry(scsi_ccb* request)
 		return;
 	}
 
+	memset(&ataData, 0, sizeof(ataData));
+
 	sata_request sreq;
 	sreq.SetData(&ataData, sizeof(ataData));
 	sreq.SetATACommand(fIsATAPI
@@ -698,12 +757,16 @@ AHCIPort::ScsiInquiry(scsi_ccb* request)
 	}
 */
 
+	memset(&scsiData, 0, sizeof(scsiData));
+
 	scsiData.device_type = fIsATAPI
 		? ataData.word_0.atapi.command_packet_set : scsi_dev_direct_access;
 	scsiData.device_qualifier = scsi_periph_qual_connected;
 	scsiData.device_type_modifier = 0;
 	scsiData.removable_medium = ataData.word_0.ata.removable_media_device;
-	scsiData.ansi_version = 2;
+	scsiData.ansi_version = 5;
+		// Set the version to SPC-3 so that scsi_periph
+		// uses READ CAPACITY (16) and attempts to read VPD pages
 	scsiData.ecma_version = 0;
 	scsiData.iso_version = 0;
 	scsiData.response_data_format = 2;
@@ -721,6 +784,7 @@ AHCIPort::ScsiInquiry(scsi_ccb* request)
 		fSectorCount = ataData.SectorCount(fUse48BitCommands, true);
 		fSectorSize = ataData.SectorSize();
 		fTrimSupported = ataData.data_set_management_support;
+		fTrimReturnsZeros = ataData.supports_read_zero_after_trim;
 		fMaxTrimRangeBlocks = B_LENDIAN_TO_HOST_INT16(
 			ataData.max_data_set_management_lba_range_blocks);
 		TRACE("lba %d, lba48 %d, fUse48BitCommands %d, sectors %" B_PRIu32
@@ -738,7 +802,7 @@ AHCIPort::ScsiInquiry(scsi_ccb* request)
 				"%sdeterministic%s.\n", fMaxTrimRangeBlocks,
 				deterministic ? "" : "non-", deterministic
 					? (ataData.supports_read_zero_after_trim
-						? ", zero" : ", random") : "");
+						? ", zero" : ", undefined") : "");
 			#endif
 		}
 	}
@@ -842,6 +906,8 @@ AHCIPort::ScsiReadCapacity(scsi_ccb* request)
 	TRACE("SectorSize %" B_PRIu32 ", SectorCount 0x%" B_PRIx64 "\n",
 		fSectorSize, fSectorCount);
 
+	memset(&scsiData, 0, sizeof(scsiData));
+
 	scsiData.block_size = B_HOST_TO_BENDIAN_INT32(fSectorSize);
 
 	if (fSectorCount <= 0xffffffff)
@@ -865,20 +931,37 @@ AHCIPort::ScsiReadCapacity16(scsi_ccb* request)
 {
 	TRACE("AHCIPort::ScsiReadCapacity16 port %d\n", fIndex);
 
+	const scsi_cmd_read_capacity_long* cmd
+		= (const scsi_cmd_read_capacity_long*)request->cdb;
 	scsi_res_read_capacity_long scsiData;
 
+	uint32 allocationLength = B_BENDIAN_TO_HOST_INT32(cmd->alloc_length);
+	size_t copySize = min_c(allocationLength, sizeof(scsiData));
+
+	if (cmd->pmi || cmd->lba || request->data_length < copySize) {
+		TRACE("invalid request\n");
+		request->subsys_status = SCSI_REQ_ABORTED;
+		gSCSI->finished(request, 1);
+		return;
+	}
+
 	TRACE("SectorSize %" B_PRIu32 ", SectorCount 0x%" B_PRIx64 "\n",
 		fSectorSize, fSectorCount);
 
+	memset(&scsiData, 0, sizeof(scsiData));
+
 	scsiData.block_size = B_HOST_TO_BENDIAN_INT32(fSectorSize);
 	scsiData.lba = B_HOST_TO_BENDIAN_INT64(fSectorCount - 1);
+	scsiData.rc_basis = 0x01;
+	scsiData.lbpme = fTrimSupported;
+	scsiData.lbprz = fTrimReturnsZeros;
 
 	if (sg_memcpy(request->sg_list, request->sg_count, &scsiData,
-			sizeof(scsiData)) < B_OK) {
+			copySize) < B_OK) {
 		request->subsys_status = SCSI_DATA_RUN_ERR;
 	} else {
 		request->subsys_status = SCSI_REQ_CMP;
-		request->data_resid = request->data_length - sizeof(scsiData);
+		request->data_resid = request->data_length - copySize;
 	}
 	gSCSI->finished(request, 1);
 }
@@ -939,108 +1022,147 @@ AHCIPort::ScsiReadWrite(scsi_ccb* request, uint64 lba, size_t sectorCount,
 void
 AHCIPort::ScsiUnmap(scsi_ccb* request, scsi_unmap_parameter_list* unmapBlocks)
 {
+	if (!fTrimSupported || fMaxTrimRangeBlocks == 0) {
+		ERROR("TRIM error: Invalid TRIM support values detected\n");
+		return;
+	}
+
 	// Determine how many blocks are supposed to be trimmed in total
-	uint32 scsiRangeCount = B_BENDIAN_TO_HOST_INT16(
+	uint32 scsiRangeCount = (uint16)B_BENDIAN_TO_HOST_INT16(
 		unmapBlocks->block_data_length) / sizeof(scsi_unmap_block_descriptor);
 
-dprintf("TRIM SCSI:\n");
-for (uint32 i = 0; i < scsiRangeCount; i++) {
-	dprintf("[%3" B_PRIu32 "] %" B_PRIu64 " : %" B_PRIu32 "\n", i,
-		(uint64)B_BENDIAN_TO_HOST_INT64(unmapBlocks->blocks[i].lba),
-		(uint32)B_BENDIAN_TO_HOST_INT32(unmapBlocks->blocks[i].block_count));
-}
+#ifdef DEBUG_TRIM
+	dprintf("TRIM: AHCI: received a SCSI UNMAP command (blocks):\n");
+	for (uint32 i = 0; i < scsiRangeCount; i++) {
+		dprintf("[%3" B_PRIu32 "] %" B_PRIu64 " : %" B_PRIu32 "\n", i,
+			(uint64)B_BENDIAN_TO_HOST_INT64(unmapBlocks->blocks[i].lba),
+			(uint32)B_BENDIAN_TO_HOST_INT32(
+				unmapBlocks->blocks[i].block_count));
+	}
+#endif
 
-	uint32 scsiIndex = 0;
-	uint32 scsiLastBlocks = 0;
-	uint32 maxLBARangeCount = fMaxTrimRangeBlocks * 512 / 8;
-		// 512 bytes per range block, 8 bytes per range
+	if (scsiRangeCount == 0) {
+		request->subsys_status = SCSI_REQ_CMP;
+		request->data_resid = 0;
+		request->device_status = SCSI_STATUS_GOOD;
+		gSCSI->finished(request, 1);
+		return;
+	}
 
-	// Split the SCSI ranges into ATA ranges as large as allowed.
-	// We assume that the SCSI unmap ranges cannot be merged together
+	size_t lbaRangeCount = 0;
+	for (uint32 i = 0; i < scsiRangeCount; i++) {
+		uint32 range
+			= B_BENDIAN_TO_HOST_INT32(unmapBlocks->blocks[i].block_count);
+		lbaRangeCount += range / DSM_MAX_RANGE_VALUE;
+		if (range % DSM_MAX_RANGE_VALUE != 0)
+			lbaRangeCount++;
+	}
+	TRACE("Total number of ATA ranges: %" B_PRIuSIZE "\n", lbaRangeCount);
 
-	while (scsiIndex < scsiRangeCount) {
-		// Determine how many LBA ranges we need for the next chunk
-		uint32 lbaRangeCount = 0;
-		for (uint32 i = scsiIndex; i < scsiRangeCount; i++) {
-			uint32 scsiBlocks = B_BENDIAN_TO_HOST_INT32(
-				unmapBlocks->blocks[i].block_count);
-			if (scsiBlocks == 0)
-				break;
-			if (i == scsiIndex)
-				scsiBlocks -= scsiLastBlocks;
+	size_t lbaRangesAllocatedSize = lbaRangeCount * sizeof(uint64);
+	// Request data is transferred in 512-byte blocks
+	if (lbaRangesAllocatedSize % 512 != 0) {
+		lbaRangesAllocatedSize += 512 - (lbaRangesAllocatedSize % 512);
+	}
+	// Apply reported device limits
+	if (lbaRangesAllocatedSize > (size_t)fMaxTrimRangeBlocks * 512) {
+		lbaRangesAllocatedSize = (size_t)fMaxTrimRangeBlocks * 512;
+	}
+	// Allocate a single buffer and re-use it between requests
+	TRACE("Allocating a %" B_PRIuSIZE "-byte buffer for ATA request ranges\n",
+		lbaRangesAllocatedSize);
+	uint64* lbaRanges = (uint64*)malloc(lbaRangesAllocatedSize);
+	if (lbaRanges == NULL) {
+		ERROR("out of memory when allocating space for %" B_PRIuSIZE
+			" unmap ranges\n", lbaRangesAllocatedSize / sizeof(uint64));
+		request->subsys_status = SCSI_REQ_ABORTED;
+		gSCSI->finished(request, 1);
+		return;
+	}
 
-			lbaRangeCount += (scsiBlocks + 65534) / 65535;
-			if (lbaRangeCount >= maxLBARangeCount) {
-				lbaRangeCount = maxLBARangeCount;
-				break;
-			}
-		}
-		if (lbaRangeCount == 0)
-			break;
+	MemoryDeleter deleter(lbaRanges);
 
-		uint32 lbaRangesSize = lbaRangeCount * sizeof(uint64);
-		uint64* lbaRanges = (uint64*)malloc(lbaRangesSize);
-		if (lbaRanges == NULL) {
-			ERROR("out of memory when allocating %" B_PRIu32 " unmap ranges\n",
-				lbaRangeCount);
-			request->subsys_status = SCSI_REQ_ABORTED;
-			gSCSI->finished(request, 1);
-			return;
+	memset(lbaRanges, 0, lbaRangesAllocatedSize);
+		// Entries with range length of 0 will be ignored
+	uint32 lbaIndex = 0;
+	for (uint32 i = 0; i < scsiRangeCount; i++) {
+		uint64 lba = B_BENDIAN_TO_HOST_INT64(unmapBlocks->blocks[i].lba);
+		uint64 length = (uint32)B_BENDIAN_TO_HOST_INT32(
+			unmapBlocks->blocks[i].block_count);
+
+		if (length == 0)
+			continue; // Length of 0 would be ignored by the device anyway
+
+		if (lba > DSM_MAX_LBA_VALUE) {
+			ERROR("LBA value is too large!"
+				" This unmap range will be skipped.\n");
+			continue;
 		}
 
-		MemoryDeleter deleter(lbaRanges);
+		// Split large ranges if needed.
+		// Range length is limited by:
+		//   - max value of the range field (DSM_MAX_RANGE_VALUE)
+		while (length > 0) {
+			uint64 ataRange = min_c(length, DSM_MAX_RANGE_VALUE);
+			lbaRanges[lbaIndex++]
+				= B_HOST_TO_LENDIAN_INT64((ataRange << 48) | lba);
 
-		for (uint32 lbaIndex = 0;
-				scsiIndex < scsiRangeCount && lbaIndex < lbaRangeCount;) {
-			uint64 scsiOffset = B_BENDIAN_TO_HOST_INT64(
-				unmapBlocks->blocks[scsiIndex].lba) + scsiLastBlocks;
-			uint32 scsiBlocksLeft = B_BENDIAN_TO_HOST_INT32(
-				unmapBlocks->blocks[scsiIndex].block_count) - scsiLastBlocks;
+			// Split into multiple requests if needed.
+			// The number of entries in a request is limited by:
+			//   - the maximum number of 512-byte blocks reported by the device
+			//   - maximum possible value of the COUNT field
+			//   - the size of our buffer
+			if (lbaIndex >= fMaxTrimRangeBlocks * DSM_RANGE_BLOCK_ENTRIES
+				|| (((lbaIndex + 1) * sizeof(uint64) + 511) / 512)
+					> DSM_MAX_COUNT_48
+				|| lbaIndex >= lbaRangesAllocatedSize / sizeof(uint64)
+				|| (i == scsiRangeCount - 1 && length <= DSM_MAX_RANGE_VALUE))
+			{
+				uint32 lbaRangeCount = lbaIndex;
+				if (lbaRangeCount % DSM_RANGE_BLOCK_ENTRIES != 0)
+					lbaRangeCount += DSM_RANGE_BLOCK_ENTRIES
+						- (lbaRangeCount % DSM_RANGE_BLOCK_ENTRIES);
+				uint32 lbaRangesSize = lbaRangeCount * sizeof(uint64);
 
-			if (scsiBlocksLeft == 0) {
-				// Ignore the rest of the ranges (they are empty)
-				scsiIndex = scsiRangeCount;
-				break;
+#ifdef DEBUG_TRIM
+				dprintf("TRIM: AHCI: sending a DATA SET MANAGEMENT command"
+					" to the device (blocks):\n");
+				for (uint32 i = 0; i < lbaRangeCount; i++) {
+					uint64 value = B_LENDIAN_TO_HOST_INT64(lbaRanges[i]);
+					dprintf("[%3" B_PRIu32 "] %" B_PRIu64 " : %" B_PRIu64 "\n", i,
+						value & (((uint64)1 << 48) - 1), value >> 48);
+				}
+#endif
+
+				ASSERT(lbaRangesSize % 512 == 0);
+				ASSERT(lbaRangesSize <= lbaRangesAllocatedSize);
+
+				sata_request sreq;
+				sreq.SetATA48Command(ATA_COMMAND_DATA_SET_MANAGEMENT, 0,
+					lbaRangesSize / 512);
+				sreq.SetFeature(1);
+				sreq.SetData(lbaRanges, lbaRangesSize);
+
+				ExecuteSataRequest(&sreq, true);
+				sreq.WaitForCompletion();
+
+				if ((sreq.CompletionStatus() & ATA_STATUS_ERROR) != 0) {
+					ERROR("trim failed (%" B_PRIu32
+						" ATA ranges)!\n", lbaRangeCount);
+					request->subsys_status = SCSI_REQ_CMP_ERR;
+					request->device_status = SCSI_STATUS_CHECK_CONDITION;
+					gSCSI->finished(request, 1);
+					return;
+				} else
+					request->subsys_status = SCSI_REQ_CMP;
+
+				lbaIndex = 0;
+				memset(lbaRanges, 0, lbaRangesSize);
 			}
 
-			while (scsiBlocksLeft > 0 && lbaIndex < lbaRangeCount) {
-				uint16 blocks = scsiBlocksLeft > 65535
-					? 65535 : (uint16)scsiBlocksLeft;
-				lbaRanges[lbaIndex++] = B_HOST_TO_LENDIAN_INT64(
-					((uint64)blocks << 48) | scsiOffset);
-
-				scsiOffset += blocks;
-				scsiLastBlocks += blocks;
-				scsiBlocksLeft -= blocks;
-			}
-
-			if (scsiBlocksLeft == 0) {
-				scsiLastBlocks = 0;
-				scsiIndex++;
-			}
+			length -= ataRange;
+			lba += ataRange;
 		}
-
-dprintf("TRIM AHCI:\n");
-for (uint32 i = 0; i < lbaRangeCount; i++) {
-	uint64 value = B_HOST_TO_LENDIAN_INT64(lbaRanges[i]);
-	dprintf("[%3" B_PRIu32 "] %" B_PRIu64 " : %" B_PRIu64 "\n", i,
-		value & (((uint64)1 << 48) - 1), value >> 48);
-}
-
-		sata_request sreq;
-		sreq.SetATA48Command(ATA_COMMAND_DATA_SET_MANAGEMENT, 0,
-			(lbaRangesSize + 511) / 512);
-		sreq.SetFeature(1);
-		sreq.SetData(lbaRanges, lbaRangesSize);
-
-		ExecuteSataRequest(&sreq);
-		sreq.WaitForCompletion();
-
-		if ((sreq.CompletionStatus() & ATA_STATUS_ERROR) != 0) {
-			ERROR("trim failed (%" B_PRIu32 " ranges)!\n", lbaRangeCount);
-			request->subsys_status = SCSI_REQ_CMP_ERR;
-		} else
-			request->subsys_status = SCSI_REQ_CMP;
 	}
 
 	request->data_resid = 0;
@@ -1301,9 +1423,15 @@ AHCIPort::ScsiExecuteRequest(scsi_ccb* request)
 			scsi_unmap_parameter_list* unmapBlocks
 				= (scsi_unmap_parameter_list*)request->data;
 			if (unmapBlocks == NULL
-				|| B_BENDIAN_TO_HOST_INT16(cmd->length) != request->data_length
-				|| B_BENDIAN_TO_HOST_INT16(unmapBlocks->data_length)
-					!= request->data_length - 1) {
+				|| (uint16)B_BENDIAN_TO_HOST_INT16(cmd->length)
+					!= request->data_length
+				|| (uint16)B_BENDIAN_TO_HOST_INT16(unmapBlocks->data_length)
+					!= request->data_length
+						- offsetof(scsi_unmap_parameter_list, block_data_length)
+				|| (uint16)B_BENDIAN_TO_HOST_INT16(
+						unmapBlocks->block_data_length)
+					!= request->data_length
+						- offsetof(scsi_unmap_parameter_list, blocks)) {
 				ERROR("%s port %d: invalid unmap parameter data length\n",
 					__func__, fIndex);
 				request->subsys_status = SCSI_REQ_ABORTED;
diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
index 0b8c802905..1622be9926 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
@@ -86,6 +86,7 @@ private:
 	bool							fPortReset;
 	bool							fError;
 	bool							fTrimSupported;
+	bool							fTrimReturnsZeros;
 	uint32							fMaxTrimRangeBlocks;
 
 	volatile fis *					fFIS;
diff --git a/src/add-ons/kernel/drivers/disk/scsi/scsi_disk/scsi_disk.cpp b/src/add-ons/kernel/drivers/disk/scsi/scsi_disk/scsi_disk.cpp
index 0d6b1188df..eba0d5ccf4 100644
--- a/src/add-ons/kernel/drivers/disk/scsi/scsi_disk/scsi_disk.cpp
+++ b/src/add-ons/kernel/drivers/disk/scsi/scsi_disk/scsi_disk.cpp
@@ -1,7 +1,8 @@
 /*
- * Copyright 2008-2013, Axel Dörfler, axeld@pinc-software.de.
- * Copyright 2002/03, Thomas Kurschel. All rights reserved.
- * Distributed under the terms of the MIT License.
+ * Copyright 2021 David Sebek, dasebek@gmail.com
+ * Copyright 2008-2013 Axel Dörfler, axeld@pinc-software.de
+ * Copyright 2002/03 Thomas Kurschel
+ * All rights reserved. Distributed under the terms of the MIT License.
  */
 
 
@@ -156,31 +157,64 @@ synchronize_cache(das_driver_info *device)
 }
 
 
-#if 0
 static status_t
 trim_device(das_driver_info* device, fs_trim_data* trimData)
 {
 	TRACE("trim_device()\n");
 
+	trimData->trimmed_size = 0;
+
 	scsi_ccb* request = device->scsi->alloc_ccb(device->scsi_device);
 	if (request == NULL)
 		return B_NO_MEMORY;
 
-	uint64 trimmedSize = 0;
+	scsi_block_range* blockRanges = (scsi_block_range*)
+		malloc(trimData->range_count * sizeof(*blockRanges));
+	if (blockRanges == NULL)
+		return B_NO_MEMORY;
+
+	MemoryDeleter deleter(blockRanges);
+
 	for (uint32 i = 0; i < trimData->range_count; i++) {
-		trimmedSize += trimData->ranges[i].size;
+		uint64 startBytes = trimData->ranges[i].offset;
+		uint64 sizeBytes = trimData->ranges[i].size;
+		uint32 blockSize = device->block_size;
+
+		// Align to a block boundary so we don't discard blocks
+		// that could also contain some other data
+		uint64 blockOffset = startBytes % blockSize;
+		if (blockOffset == 0) {
+			blockRanges[i].lba = startBytes / blockSize;
+			blockRanges[i].size = sizeBytes / blockSize;
+		} else {
+			blockRanges[i].lba = startBytes / blockSize + 1;
+			blockRanges[i].size = (sizeBytes - (blockSize - blockOffset))
+				/ blockSize;
+		}
 	}
+
+	// Check ranges against device capacity and make them fit
+	for (uint32 i = 0; i < trimData->range_count; i++) {
+		if (blockRanges[i].lba >= device->capacity) {
+			dprintf("trim_device(): range offset (LBA) %" B_PRIu64
+				" exceeds device capacity %" B_PRIu64 "\n",
+				blockRanges[i].lba, device->capacity);
+			return B_BAD_VALUE;
+		}
+		uint64 maxSize = device->capacity - blockRanges[i].lba;
+		blockRanges[i].size = min_c(blockRanges[i].size, maxSize);
+	}
+
+	uint64 trimmedBlocks;
 	status_t status = sSCSIPeripheral->trim_device(device->scsi_periph_device,
-		request, (scsi_block_range*)&trimData->ranges[0],
-		trimData->range_count);
+		request, blockRanges, trimData->range_count, &trimmedBlocks);
 
 	device->scsi->free_ccb(request);
-	if (status == B_OK)
-		trimData->trimmed_size = trimmedSize;
+	// Some blocks may have been trimmed even if trim_device returns a failure
+	trimData->trimmed_size = trimmedBlocks * device->block_size;
 
 	return status;
 }
-#endif
 
 
 static int
@@ -415,7 +449,6 @@ das_ioctl(void* cookie, uint32 op, void* buffer, size_t length)
 		case B_FLUSH_DRIVE_CACHE:
 			return synchronize_cache(info);
 
-#if 0
 		case B_TRIM_DEVICE:
 		{
 			// We know the buffer is kernel-side because it has been
@@ -423,7 +456,6 @@ das_ioctl(void* cookie, uint32 op, void* buffer, size_t length)
 			ASSERT(IS_KERNEL_ADDRESS(buffer));
 			return trim_device(info, (fs_trim_data*)buffer);
 		}
-#endif
 
 		default:
 			return sSCSIPeripheral->ioctl(handle->scsi_periph_handle, op,
diff --git a/src/add-ons/kernel/generic/scsi_periph/block.cpp b/src/add-ons/kernel/generic/scsi_periph/block.cpp
index 000726e7d9..e9b4d2dc73 100644
--- a/src/add-ons/kernel/generic/scsi_periph/block.cpp
+++ b/src/add-ons/kernel/generic/scsi_periph/block.cpp
@@ -1,8 +1,8 @@
 /*
- * Copyright 2004-2013, Haiku, Inc. All RightsReserved.
- * Copyright 2002-2003, Thomas Kurschel. All rights reserved.
- *
- * Distributed under the terms of the MIT License.
+ * Copyright 2021 David Sebek, dasebek@gmail.com
+ * Copyright 2004-2013 Haiku, Inc.
+ * Copyright 2002-2003 Thomas Kurschel
+ * All rights reserved. Distributed under the terms of the MIT License.
  */
 
 
@@ -16,13 +16,320 @@
 #include "scsi_periph_int.h"
 
 
-status_t
-periph_check_capacity(scsi_periph_device_info *device, scsi_ccb *request)
-{
-	scsi_res_read_capacity capacityResult;
-	scsi_cmd_read_capacity *cmd = (scsi_cmd_read_capacity *)request->cdb;
-	uint64 capacity;
+// UNMAP command limits
+#define UNMAP_MAX_LBA_VALUE				UINT64_MAX
+#define UNMAP_MAX_BLOCK_COUNT_VALUE		UINT32_MAX
+#define UNMAP_MAX_DESCRIPTORS			4095
+	// Limit imposed by the UNMAP command structure
+#define UNMAP_DEFAULT_DESCRIPTORS		255
+	// Reasonable default (?) when not specified by the device
+
+// WRITE SAME (16) command limits
+#define WS16_MAX_LBA_VALUE				UINT64_MAX
+#define WS16_MAX_BLOCK_COUNT_VALUE		UINT32_MAX
+
+// WRITE SAME (10) command limits
+#define WS10_MAX_LBA_VALUE				UINT32_MAX
+#define WS10_MAX_BLOCK_COUNT_VALUE		UINT16_MAX
+
+
+struct CapacityInfo {
+	// Result of the READ CAPACITY command
+	bool capacityFilled;
+	uint64 lastLba;
 	uint32 blockSize;
+
+	// Provisioining info from READ CAPACITY
+	bool provisioningFilled;
+	bool lbpme;
+	bool lbprz;
+};
+
+
+struct UnmapSupport {
+	// UNMAP commands supported by the device
+	bool commandSupportFilled;
+	bool unmapSupported;
+	bool ws16Supported;
+	bool ws10Supported;
+
+	// Block limits for UNMAP commands
+	bool blockLimitsFilled;
+	uint32 maxUnmapLbaCount;
+	uint32 maxUnmapDescriptorCount;
+	uint64 maxWritesameLength;
+};
+
+
+static bool
+prefer_read_capacity_16(scsi_periph_device_info* device)
+{
+	const scsi_res_inquiry* inquiryData = NULL;
+	size_t inquiryDataLength;
+
+	if (gDeviceManager->get_attr_raw(device->node, SCSI_DEVICE_INQUIRY_ITEM,
+				(const void**)&inquiryData, &inquiryDataLength, true) != B_OK
+		|| inquiryDataLength != sizeof(*inquiryData)) {
+		return false;
+	}
+
+	if (inquiryData->protect)
+		return true;
+
+	if (inquiryData->ansi_version > 0x04 /* SPC-2 */)
+		return true;
+
+	return false;
+}
+
+
+static bool
+vpd_pages_supported(scsi_periph_device_info* device)
+{
+	const scsi_res_inquiry* inquiryData = NULL;
+	size_t inquiryDataLength;
+
+	if (gDeviceManager->get_attr_raw(device->node, SCSI_DEVICE_INQUIRY_ITEM,
+				(const void**)&inquiryData, &inquiryDataLength, true) != B_OK
+		|| inquiryDataLength != sizeof(*inquiryData)) {
+		return false;
+	}
+
+	if (inquiryData->ansi_version >= 0x04 /* SPC-2 */)
+		return true;
+
+	return false;
+}
+
+
+static status_t
+read_capacity_10(scsi_periph_device_info* device, scsi_ccb* request,
+	CapacityInfo* capacityInfo)
+{
+	capacityInfo->capacityFilled = false;
+	capacityInfo->provisioningFilled = false;
+
+	scsi_res_read_capacity capacityResult;
+	memset(&capacityResult, 0, sizeof(capacityResult));
+
+	scsi_cmd_read_capacity* cmd = (scsi_cmd_read_capacity*)request->cdb;
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->opcode = SCSI_OP_READ_CAPACITY;
+	// we don't set PMI (partial medium indicator) as we want the whole capacity;
+	// in this case, all other parameters must be zero
+
+	request->flags = SCSI_DIR_IN;
+	request->cdb_length = sizeof(*cmd);
+	request->sort = -1;
+	request->timeout = device->std_timeout;
+
+	request->data = (uint8*)&capacityResult;
+	request->data_length = sizeof(capacityResult);
+	request->sg_list = NULL;
+
+	status_t res = periph_safe_exec(device, request);
+
+	if (res == B_OK && request->data_resid == 0) {
+		capacityInfo->capacityFilled = true;
+		capacityInfo->lastLba
+			= (uint32)B_BENDIAN_TO_HOST_INT32(capacityResult.lba);
+		capacityInfo->blockSize
+			= B_BENDIAN_TO_HOST_INT32(capacityResult.block_size);
+	}
+
+	return res;
+}
+
+
+static status_t
+read_capacity_16(scsi_periph_device_info* device, scsi_ccb* request,
+	CapacityInfo* capacityInfo)
+{
+	capacityInfo->capacityFilled = false;
+	capacityInfo->provisioningFilled = false;
+
+	scsi_res_read_capacity_long capacityLongResult;
+	memset(&capacityLongResult, 0, sizeof(capacityLongResult));
+
+	scsi_cmd_read_capacity_long* cmd
+		= (scsi_cmd_read_capacity_long*)request->cdb;
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->opcode = SCSI_OP_SERVICE_ACTION_IN;
+	cmd->service_action = SCSI_SAI_READ_CAPACITY_16;
+	cmd->alloc_length = B_HOST_TO_BENDIAN_INT32(sizeof(capacityLongResult));
+
+	request->flags = SCSI_DIR_IN;
+	request->cdb_length = sizeof(*cmd);
+	request->sort = -1;
+	request->timeout = device->std_timeout;
+
+	request->data = (uint8*)&capacityLongResult;
+	request->data_length = sizeof(capacityLongResult);
+	request->sg_list = NULL;
+
+	status_t res = periph_safe_exec(device, request);
+
+	if (res == B_OK && request->data_resid
+			<= (int32)sizeof(scsi_res_read_capacity_long) - 12) {
+		// At least the last LBA and sector size have been transfered
+		capacityInfo->capacityFilled = true;
+		capacityInfo->lastLba
+			= B_BENDIAN_TO_HOST_INT64(capacityLongResult.lba);
+		capacityInfo->blockSize
+			= B_BENDIAN_TO_HOST_INT32(capacityLongResult.block_size);
+	}
+
+	if (res == B_OK && request->data_resid
+			<= (int32)sizeof(scsi_res_read_capacity_long) - 15) {
+		// lbpme and lbprz bits were received too
+		capacityInfo->provisioningFilled = true;
+		capacityInfo->lbpme = capacityLongResult.lbpme;
+		capacityInfo->lbprz = capacityLongResult.lbprz;
+	}
+
+	return res;
+}
+
+
+static status_t
+get_unmap_commands(scsi_periph_device_info* device, scsi_ccb* request,
+	UnmapSupport* unmapSupport)
+{
+	unmapSupport->commandSupportFilled = false;
+
+	scsi_page_lb_provisioning vpdProvisioning;
+	memset(&vpdProvisioning, 0, sizeof(vpdProvisioning));
+	status_t vpdStatus = vpd_page_get(device, request,
+		SCSI_PAGE_LB_PROVISIONING, &vpdProvisioning, sizeof(vpdProvisioning));
+
+	if (vpdStatus == B_OK
+		&& request->data_resid <= (int32)sizeof(scsi_page_lb_provisioning) - 6
+		&& vpdProvisioning.page_code == SCSI_PAGE_LB_PROVISIONING
+		&& B_BENDIAN_TO_HOST_INT16(vpdProvisioning.page_length) >= 2) {
+		unmapSupport->commandSupportFilled = true;
+		unmapSupport->unmapSupported = vpdProvisioning.lbpu;
+		unmapSupport->ws16Supported = vpdProvisioning.lbpws;
+		unmapSupport->ws10Supported = vpdProvisioning.lbpws10;
+	}
+
+	if (vpdStatus == B_BAD_VALUE)
+		return B_ERROR;
+
+	return vpdStatus;
+}
+
+
+static status_t
+get_unmap_limits(scsi_periph_device_info* device, scsi_ccb* request,
+	UnmapSupport* unmapSupport)
+{
+	unmapSupport->blockLimitsFilled = false;
+
+	scsi_page_block_limits vpdBlockLimits;
+	memset(&vpdBlockLimits, 0, sizeof(vpdBlockLimits));
+	status_t vpdStatus = vpd_page_get(device, request,
+		SCSI_PAGE_BLOCK_LIMITS, &vpdBlockLimits, sizeof(vpdBlockLimits));
+
+	if (vpdStatus == B_OK
+		&& request->data_resid <= (int32)sizeof(scsi_page_block_limits) - 44
+		&& vpdBlockLimits.page_code == SCSI_PAGE_BLOCK_LIMITS
+		&& B_BENDIAN_TO_HOST_INT16(vpdBlockLimits.page_length) == 0x3c) {
+		unmapSupport->blockLimitsFilled = true;
+		unmapSupport->maxUnmapLbaCount = B_BENDIAN_TO_HOST_INT32(
+			vpdBlockLimits.max_unmap_lba_count);
+		unmapSupport->maxUnmapDescriptorCount = B_BENDIAN_TO_HOST_INT32(
+			vpdBlockLimits.max_unmap_blk_count);
+		unmapSupport->maxWritesameLength = B_BENDIAN_TO_HOST_INT64(
+			vpdBlockLimits.max_write_same_length);
+	}
+
+	if (vpdStatus == B_BAD_VALUE)
+		return B_ERROR;
+
+	return vpdStatus;
+}
+
+
+static void
+determine_unmap_support(const UnmapSupport* unmapSupport,
+	enum trim_command* unmapCommand, uint32* maxLbaCount,
+	uint32* maxDescriptorCount)
+{
+#ifdef DEBUG_TRIM
+	if (unmapSupport->commandSupportFilled)
+		dprintf("TRIM: device reports (LBP VPD): LBPU = %d, LBPWS = %d,"
+			" LBPWS10 = %d\n", unmapSupport->unmapSupported,
+			unmapSupport->ws16Supported, unmapSupport->ws10Supported);
+	else
+		dprintf("TRIM: could not get the LBP VPD of the device\n");
+	if (unmapSupport->blockLimitsFilled)
+		dprintf("TRIM: device reports (Block Limits VPD):"
+			"\nTRIM: MAXIMUM UNMAP LBA COUNT = %" B_PRIu32
+			"\nTRIM: MAXIMUM UNMAP BLOCK DESCRIPTOR COUNT = %" B_PRIu32
+			"\nTRIM: MAXIMUM WRITESAME LENGTH = %" B_PRIu64 "\n",
+			unmapSupport->maxUnmapLbaCount,
+			unmapSupport->maxUnmapDescriptorCount,
+			unmapSupport->maxWritesameLength);
+	else
+		dprintf("TRIM: could not get Block Limits VPD of the device\n");
+#endif
+
+	*unmapCommand = TRIM_NONE;
+	*maxLbaCount = 0;
+	*maxDescriptorCount = 0;
+
+	if (!unmapSupport->commandSupportFilled
+		|| !unmapSupport->blockLimitsFilled)
+		return;
+
+	if (unmapSupport->unmapSupported
+		&& unmapSupport->maxUnmapLbaCount > 0
+		&& unmapSupport->maxUnmapDescriptorCount > 0) {
+		*unmapCommand = TRIM_UNMAP;
+		*maxLbaCount = unmapSupport->maxUnmapLbaCount;
+		if (unmapSupport->maxUnmapDescriptorCount == UINT32_MAX
+			|| unmapSupport->maxUnmapDescriptorCount > UNMAP_MAX_DESCRIPTORS) {
+			// Choose a reasonable value instead
+			*maxDescriptorCount = UNMAP_DEFAULT_DESCRIPTORS;
+		} else {
+			*maxDescriptorCount = unmapSupport->maxUnmapDescriptorCount;
+		}
+	}
+
+	if (*unmapCommand == TRIM_NONE && unmapSupport->ws16Supported) {
+		uint64 maxLength = unmapSupport->maxWritesameLength;
+		if (maxLength == 0) {
+			// WRITE SAME limit not reported, try UNMAP limit instead
+			if (unmapSupport->maxUnmapLbaCount > 0)
+				maxLength = unmapSupport->maxUnmapLbaCount;
+			else
+				maxLength = WS16_MAX_BLOCK_COUNT_VALUE;
+		}
+		*unmapCommand = TRIM_WRITESAME16;
+		*maxLbaCount = min_c(maxLength, WS16_MAX_BLOCK_COUNT_VALUE);
+		*maxDescriptorCount = 1;
+	}
+
+	if (*unmapCommand == TRIM_NONE && unmapSupport->ws10Supported) {
+		uint64 maxLength = unmapSupport->maxWritesameLength;
+		if (maxLength == 0) {
+			// WRITE SAME limit not reported, try UNMAP limit instead
+			if (unmapSupport->maxUnmapLbaCount > 0)
+				maxLength = unmapSupport->maxUnmapLbaCount;
+			else
+				maxLength = WS10_MAX_BLOCK_COUNT_VALUE;
+		}
+		*unmapCommand = TRIM_WRITESAME10;
+		*maxLbaCount = min_c(maxLength, WS10_MAX_BLOCK_COUNT_VALUE);
+		*maxDescriptorCount = 1;
+	}
+}
+
+
+status_t
+periph_check_capacity(scsi_periph_device_info* device, scsi_ccb* request)
+{
+	CapacityInfo capacityInfo = {0};
 	status_t res;
 
 	SHOW_FLOW(3, "%p, %p", device, request);
@@ -32,71 +339,100 @@ periph_check_capacity(scsi_periph_device_info *device, scsi_ccb *request)
 	if (device->callbacks->set_capacity == NULL)
 		return B_OK;
 
-	request->flags = SCSI_DIR_IN;
+	if (prefer_read_capacity_16(device)) {
+		SHOW_FLOW0(3, "READ CAPACITY 16 tried first");
+		res = read_capacity_16(device, request, &capacityInfo);
 
-	request->data = (uint8*)&capacityResult;
-	request->data_length = sizeof(capacityResult);
-	request->cdb_length = sizeof(scsi_cmd_read_capacity);
-	request->timeout = device->std_timeout;
-	request->sort = -1;
-	request->sg_list = NULL;
+		if (res == B_ERROR) {
+			SHOW_FLOW0(3, "READ CAPACITY 16 failed, trying READ CAPACITY 10");
+			res = read_capacity_10(device, request, &capacityInfo);
+		}
+	} else {
+		SHOW_FLOW0(3, "READ CAPACITY 10 tried first");
+		res = read_capacity_10(device, request, &capacityInfo);
 
-	memset(cmd, 0, sizeof(*cmd));
-	cmd->opcode = SCSI_OP_READ_CAPACITY;
-	// we don't set PMI (partial medium indicator) as we want the whole capacity;
-	// in this case, all other parameters must be zero
-
-	res = periph_safe_exec(device, request);
-
-	if (res == B_DEV_MEDIA_CHANGED) {
-		// in this case, the error handler has already called check_capacity
-		// recursively, so we ignore our (invalid) result
-		SHOW_FLOW0( 3, "ignore result because medium change" );
-		return B_DEV_MEDIA_CHANGED;
+		if (res == B_OK && capacityInfo.capacityFilled
+			&& capacityInfo.lastLba == UINT32_MAX) {
+			SHOW_FLOW0(3, "Device is too large, trying READ CAPACITY 16");
+			res = read_capacity_16(device, request, &capacityInfo);
+		}
 	}
 
-	mutex_lock(&device->mutex);
+	uint64 capacity;
+	uint32 blockSize;
 
-	if (res == B_OK && request->data_resid == 0) {
-		capacity = B_BENDIAN_TO_HOST_INT32(capacityResult.lba);
-
-		if (capacity == UINT_MAX) {
-			mutex_unlock(&device->mutex);
-
-			scsi_cmd_read_capacity_long *cmd
-				= (scsi_cmd_read_capacity_long *)request->cdb;
-
-			scsi_res_read_capacity_long capacityLongResult;
-			request->data = (uint8*)&capacityLongResult;
-			request->data_length = sizeof(capacityLongResult);
-			request->cdb_length = sizeof(scsi_cmd_read_capacity_long);
-
-			memset(cmd, 0, sizeof(*cmd));
-			cmd->opcode = SCSI_OP_SERVICE_ACTION_IN;
-			cmd->service_action = SCSI_SAI_READ_CAPACITY_16;
-
-			res = periph_safe_exec(device, request);
-
-			mutex_lock(&device->mutex);
-
-			if (res == B_OK && request->data_resid == 0) {
-				capacity = B_BENDIAN_TO_HOST_INT64(capacityLongResult.lba);
-			} else
-				capacity = 0;
-		}
-
-		// the command returns the index of the _last_ block,
-		// i.e. the size is one larger
-		++capacity;
-
-		blockSize = B_BENDIAN_TO_HOST_INT32(capacityResult.block_size);
+	if (capacityInfo.capacityFilled) {
+		capacity = capacityInfo.lastLba + 1;
+		blockSize = capacityInfo.blockSize;
 	} else {
 		capacity = 0;
 		blockSize = 0;
 	}
 
-	SHOW_FLOW(3, "capacity = %" B_PRId64 ", block_size = %" B_PRId32, capacity,
-		blockSize);
+	enum trim_command unmapCommand = TRIM_NONE;
+	uint32 maxLbaCount = 0;
+	uint32 maxDescriptorCount = 0;
+
+	if (capacityInfo.provisioningFilled
+		&& capacityInfo.lbpme
+		&& vpd_pages_supported(device)) {
+		UnmapSupport unmapSupport = {0};
+
+		// Don't fail if the device doesn't support the command
+		// but fail if some other error happens
+		if (res == B_OK) {
+			status_t vpdStatus = get_unmap_commands(device, request,
+				&unmapSupport);
+			if (vpdStatus != B_OK && vpdStatus != B_ERROR)
+				res = vpdStatus;
+		}
+
+		if (res == B_OK) {
+			status_t vpdStatus = get_unmap_limits(device, request,
+				&unmapSupport);
+			if (vpdStatus != B_OK && vpdStatus != B_ERROR)
+				res = vpdStatus;
+		}
+
+		determine_unmap_support(&unmapSupport, &unmapCommand,
+				&maxLbaCount, &maxDescriptorCount);
+
+		if (maxLbaCount == 0 || maxDescriptorCount == 0)
+			unmapCommand = TRIM_NONE;
+	}
+
+	if (res == B_DEV_MEDIA_CHANGED) {
+		// in this case, the error handler has already called check_capacity
+		// recursively, so we ignore our (invalid) result
+		SHOW_FLOW0(3, "ignore result because medium change");
+		return B_DEV_MEDIA_CHANGED;
+	}
+
+	if (res == B_OK && !capacityInfo.capacityFilled)
+		// Although the capacity and block size will be set to 0 in this case,
+		// it is also better to inform the caller that these values were not
+		// reported by the device
+		res = B_ERROR;
+
+	SHOW_FLOW(3, "capacity = %" B_PRIu64 ", block_size = %" B_PRIu32
+		" (%sreported)", capacity, blockSize,
+		capacityInfo.capacityFilled ? "" : "not ");
+	SHOW_INFO(1, "TRIM: Setting trim support to %s",
+		unmapCommand == TRIM_NONE ? "disabled"
+			: unmapCommand == TRIM_UNMAP ? "UNMAP"
+			: unmapCommand == TRIM_WRITESAME16 ? "WRITE SAME (16)"
+			: unmapCommand == TRIM_WRITESAME10 ? "WRITE SAME (10)"
+			: "unknown");
+	SHOW_FLOW(3, "TRIM: Block limits: size = %" B_PRIu32
+		", descriptors = %" B_PRIu32, maxLbaCount, maxDescriptorCount);
+
+	mutex_lock(&device->mutex);
+		// Was there a reason why this mutex
+		// was previously locked much earlier?
+
+	device->unmap_command = unmapCommand;
+	device->max_unmap_lba_count = maxLbaCount;
+	device->max_unmap_descriptor_count = maxDescriptorCount;
 
 	device->block_size = blockSize;
 
@@ -118,61 +454,341 @@ periph_check_capacity(scsi_periph_device_info *device, scsi_ccb *request)
 }
 
 
-status_t
-periph_trim_device(scsi_periph_device_info *device, scsi_ccb *request,
-	scsi_block_range* ranges, uint32 rangeCount)
+static status_t
+trim_unmap(scsi_periph_device_info* device, scsi_ccb* request,
+	scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks)
 {
-	size_t unmapBlockSize = (rangeCount - 1)
+	uint64 maxLength = UNMAP_MAX_BLOCK_COUNT_VALUE;
+	uint64 maxBlocksInRequest = device->max_unmap_lba_count;
+	uint32 maxDescriptors = device->max_unmap_descriptor_count;
+
+	*trimmedBlocks = 0;
+
+	// Allocate a single buffer and re-use it between requests
+	size_t expectedDescriptorCount = 0;
+	for (uint32 i = 0; i < rangeCount; i++) {
+		expectedDescriptorCount += ranges[i].size / maxLength;
+		if (ranges[i].size % maxLength != 0)
+			expectedDescriptorCount++;
+	}
+	expectedDescriptorCount = min_c(expectedDescriptorCount, maxDescriptors);
+
+	size_t unmapListAllocatedSize = (expectedDescriptorCount - 1)
 			* sizeof(scsi_unmap_block_descriptor)
 		+ sizeof(scsi_unmap_parameter_list);
 
-	// TODO: check block limits VPD page
-	// TODO: instead of failing, we should try to complete the request in
-	// several passes.
-	if (unmapBlockSize > 65536 || rangeCount == 0)
-		return B_BAD_VALUE;
-
-	scsi_unmap_parameter_list* unmapBlocks
-		= (scsi_unmap_parameter_list*)malloc(unmapBlockSize);
-	if (unmapBlocks == NULL)
+	scsi_unmap_parameter_list* unmapList
+		= (scsi_unmap_parameter_list*)malloc(unmapListAllocatedSize);
+	if (unmapList == NULL)
 		return B_NO_MEMORY;
 
-	MemoryDeleter deleter(unmapBlocks);
-
-	// Prepare request data
-	memset(unmapBlocks, 0, unmapBlockSize);
-	unmapBlocks->data_length = B_HOST_TO_BENDIAN_INT16(unmapBlockSize - 1);
-	unmapBlocks->block_data_length
-		= B_HOST_TO_BENDIAN_INT16(unmapBlockSize - 7);
+	MemoryDeleter deleter(unmapList);
 
+	status_t status = B_OK;
+	uint32 descriptorIndex = 0;
+	uint64 trimmedBlocksInRequest = 0;
+	memset(unmapList, 0, unmapListAllocatedSize);
 	for (uint32 i = 0; i < rangeCount; i++) {
-		unmapBlocks->blocks[i].lba = B_HOST_TO_BENDIAN_INT64(
-			ranges[i].offset / device->block_size);
-		unmapBlocks->blocks[i].block_count = B_HOST_TO_BENDIAN_INT32(
-			ranges[i].size / device->block_size);
+		uint64 lba = ranges[i].lba;
+		uint64 length = ranges[i].size;
+
+		if (length == 0)
+			continue; // Length of 0 would be ignored by the device anyway
+
+		if (lba > UNMAP_MAX_LBA_VALUE) {
+			SHOW_ERROR0(1, "LBA value is too large!"
+				" This unmap range will be skipped.");
+			continue;
+		}
+
+		// Split large ranges if needed.
+		// Range length is limited by:
+		//   - the UNMAP_MAX_BLOCK_COUNT_VALUE constant
+		//   - the total number of LBAs in one UNMAP command is limited by
+		//     the MAX UNMAP LBA COUNT field in the Block Limits VPD page
+		while (length > 0) {
+			uint64 trimLength = min_c(length, maxLength);
+			trimLength = min_c(trimLength,
+					maxBlocksInRequest - trimmedBlocksInRequest);
+			unmapList->blocks[descriptorIndex].lba
+				= B_HOST_TO_BENDIAN_INT64(lba);
+			unmapList->blocks[descriptorIndex].block_count
+				= B_HOST_TO_BENDIAN_INT32(trimLength);
+			descriptorIndex++;
+			trimmedBlocksInRequest += trimLength;
+
+			// Split into multiple requests if needed.
+			// The number of UNMAP block descriptors is limited by:
+			//   - the number of block descriptors cannot exceed the
+			//     MAXIMUM UNMAP PARAMETER COUNT value in the Block Limits VPD
+			//   - the size of our buffer
+			//   - what fits in one UNMAP command
+			//   - the total number of LBAs in one UNMAP command is limited by
+			//     the MAX UNMAP LBA COUNT field in the Block Limits VPD page
+			if (descriptorIndex >= maxDescriptors
+				|| descriptorIndex >= expectedDescriptorCount
+				|| descriptorIndex >= UNMAP_MAX_DESCRIPTORS
+				|| trimmedBlocksInRequest >= maxBlocksInRequest
+				|| (i == rangeCount - 1 && length <= maxLength))
+			{
+				uint16 unmapListSize = (descriptorIndex - 1)
+						* sizeof(scsi_unmap_block_descriptor)
+					+ sizeof(scsi_unmap_parameter_list);
+				unmapList->data_length = B_HOST_TO_BENDIAN_INT16(unmapListSize
+					- offsetof(scsi_unmap_parameter_list, block_data_length));
+				unmapList->block_data_length
+					= B_HOST_TO_BENDIAN_INT16(unmapListSize
+						- offsetof(scsi_unmap_parameter_list, blocks));
+
+				scsi_cmd_unmap* cmd = (scsi_cmd_unmap*)request->cdb;
+				memset(cmd, 0, sizeof(*cmd));
+				cmd->opcode = SCSI_OP_UNMAP;
+				cmd->length = B_HOST_TO_BENDIAN_INT16(unmapListSize);
+
+				request->flags = SCSI_DIR_OUT;
+				request->cdb_length = sizeof(*cmd);
+				request->sort = B_BENDIAN_TO_HOST_INT64(
+					unmapList->blocks[0].lba);
+				request->timeout = device->std_timeout;
+
+				request->data = (uint8*)unmapList;
+				request->data_length = unmapListSize;
+				request->sg_list = NULL;
+
+				SHOW_FLOW(3, "UNMAP data used %" B_PRIu16
+					" of %" B_PRIuSIZE " allocated bytes",
+					unmapListSize, unmapListAllocatedSize);
+
+#ifdef DEBUG_TRIM
+				uint16 scsiRangeCount = (uint16)B_BENDIAN_TO_HOST_INT16(
+					unmapList->block_data_length)
+					/ sizeof(scsi_unmap_block_descriptor);
+				uint64 count = 0;
+				dprintf("TRIM: SCSI: sending an UNMAP command to"
+					" the device (blocks):\n");
+				for (uint16 i = 0; i < scsiRangeCount; i++) {
+					dprintf("[%3" B_PRIu16 "] %" B_PRIu64 " : %" B_PRIu32 "\n",
+						i, (uint64)B_BENDIAN_TO_HOST_INT64(
+							unmapList->blocks[i].lba),
+						(uint32)B_BENDIAN_TO_HOST_INT32(
+							unmapList->blocks[i].block_count));
+					count += (uint32)B_BENDIAN_TO_HOST_INT32(
+							unmapList->blocks[i].block_count);
+				}
+				if (device->max_unmap_lba_count >= count)
+					dprintf("TRIM: SCSI: Previous UNMAP command would fit %"
+						B_PRIu64 " more LBAs\n",
+						device->max_unmap_lba_count - count);
+				else
+					dprintf("TRIM: SCSI: Previous UNMAP ranges exceed the"
+						" device limit!\n");
+#endif /* DEBUG_TRIM */
+
+				status = periph_safe_exec(device, request);
+
+				// peripheral layer only creates "read" error
+				if (status == B_DEV_READ_ERROR)
+					return B_DEV_WRITE_ERROR;
+				else if (status != B_OK)
+					return status;
+
+				*trimmedBlocks += trimmedBlocksInRequest;
+
+				descriptorIndex = 0;
+				trimmedBlocksInRequest = 0;
+				memset(unmapList, 0, unmapListSize);
+			}
+
+			length -= trimLength;
+			lba += trimLength;
+		}
 	}
 
-	request->flags = SCSI_DIR_OUT;
-	request->sort = ranges[0].offset / device->block_size;
-	request->timeout = device->std_timeout;
-
-	scsi_cmd_unmap* cmd = (scsi_cmd_unmap*)request->cdb;
-
-	memset(cmd, 0, sizeof(*cmd));
-	cmd->opcode = SCSI_OP_UNMAP;
-	cmd->length = B_HOST_TO_BENDIAN_INT16(unmapBlockSize);
-
-	request->data = (uint8*)unmapBlocks;
-	request->data_length = unmapBlockSize;
-
-	request->cdb_length = sizeof(*cmd);
-
-	status_t status = periph_safe_exec(device, request);
-
-	// peripheral layer only creates "read" error
-	if (status == B_DEV_READ_ERROR)
-		return B_DEV_WRITE_ERROR;
-
 	return status;
 }
 
+
+static status_t
+trim_writesame16(scsi_periph_device_info* device, scsi_ccb* request,
+	scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks)
+{
+	status_t status = B_OK;
+	*trimmedBlocks = 0;
+
+	for (uint32 i = 0; i < rangeCount; i++) {
+		uint64 lba = ranges[i].lba;
+		uint64 length = ranges[i].size;
+
+		if (length == 0)
+			continue; // length of 0 would mean the rest of the device!
+
+		if (lba > WS16_MAX_LBA_VALUE) {
+			SHOW_ERROR0(1, "LBA value is too large!"
+				" This unmap range will be skipped.");
+			continue;
+		}
+
+		// Split the range into multiple requests if needed
+		uint64 maxLength = min_c(device->max_unmap_lba_count,
+				WS16_MAX_BLOCK_COUNT_VALUE);
+		while (length > 0) {
+			uint64 trimLength = min_c(length, maxLength);
+			if (trimLength == 0) {
+				SHOW_ERROR0(1,
+					"Error: Length of zero in WRITE SAME (16) detected");
+				break;
+			}
+
+			void* block = malloc(device->block_size);
+			if (block == NULL)
+				return B_NO_MEMORY;
+			MemoryDeleter deleter(block);
+			memset(block, 0, device->block_size);
+
+			scsi_cmd_wsame_16* cmd = (scsi_cmd_wsame_16*)request->cdb;
+			memset(cmd, 0, sizeof(*cmd));
+			cmd->opcode = SCSI_OP_WRITE_SAME_16;
+			cmd->unmap = 1;
+			cmd->lba = B_HOST_TO_BENDIAN_INT64(lba);
+			cmd->length = B_HOST_TO_BENDIAN_INT32(trimLength);
+			//cmd->ndob = 1; // no data is needed if this bit is enabled
+
+			request->flags = SCSI_DIR_OUT;
+			request->cdb_length = sizeof(*cmd);
+			request->sort = lba;
+			request->timeout = device->std_timeout;
+
+			request->data = (uint8*)block;
+			request->data_length = device->block_size;
+			request->sg_list = NULL;
+
+#ifdef DEBUG_TRIM
+			dprintf("TRIM: SCSI: sending a WRITE SAME (16) command to"
+				" the device (blocks):\n");
+			dprintf("%" B_PRIu64 " : %" B_PRIu32 "\n",
+				(uint64)B_BENDIAN_TO_HOST_INT64(cmd->lba),
+				(uint32)B_BENDIAN_TO_HOST_INT32(cmd->length));
+#endif
+
+			status = periph_safe_exec(device, request);
+
+			// peripheral layer only creates "read" error
+			if (status == B_DEV_READ_ERROR)
+				return B_DEV_WRITE_ERROR;
+			else if (status != B_OK)
+				return status;
+
+			*trimmedBlocks += trimLength;
+			length -= trimLength;
+			lba += trimLength;
+		}
+	}
+
+	return status;
+}
+
+
+static status_t
+trim_writesame10(scsi_periph_device_info* device, scsi_ccb* request,
+	scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks)
+{
+	status_t status = B_OK;
+	*trimmedBlocks = 0;
+
+	for (uint32 i = 0; i < rangeCount; i++) {
+		uint64 lba = ranges[i].lba;
+		uint64 length = ranges[i].size;
+
+		if (length == 0)
+			continue; // length of 0 would mean the rest of the device!
+
+		if (lba > WS10_MAX_LBA_VALUE) {
+			SHOW_ERROR0(1, "LBA value is too large!"
+				" This unmap range will be skipped.");
+			continue;
+		}
+
+		// Split the range into multiple requests if needed
+		uint64 maxLength = min_c(device->max_unmap_lba_count,
+				WS10_MAX_BLOCK_COUNT_VALUE);
+		while (length > 0) {
+			uint64 trimLength = min_c(length, maxLength);
+			if (trimLength == 0) {
+				SHOW_ERROR0(1,
+					"Error: Length of zero in WRITE SAME (10) detected");
+				break;
+			}
+
+			void* block = malloc(device->block_size);
+			if (block == NULL)
+				return B_NO_MEMORY;
+			MemoryDeleter deleter(block);
+			memset(block, 0, device->block_size);
+
+			scsi_cmd_wsame_10* cmd = (scsi_cmd_wsame_10*)request->cdb;
+			memset(cmd, 0, sizeof(*cmd));
+			cmd->opcode = SCSI_OP_WRITE_SAME_10;
+			cmd->unmap = 1;
+			cmd->lba = B_HOST_TO_BENDIAN_INT32(lba);
+			cmd->length = B_HOST_TO_BENDIAN_INT16(trimLength);
+
+			request->flags = SCSI_DIR_OUT;
+			request->cdb_length = sizeof(*cmd);
+			request->sort = lba;
+			request->timeout = device->std_timeout;
+
+			request->data = (uint8*)block;
+			request->data_length = device->block_size;
+			request->sg_list = NULL;
+
+#ifdef DEBUG_TRIM
+			dprintf("TRIM: SCSI: sending a WRITE SAME (10) command to"
+				" the device (blocks):\n");
+			dprintf("%" B_PRIu32 " : %" B_PRIu16 "\n",
+				(uint32)B_BENDIAN_TO_HOST_INT32(cmd->lba),
+				(uint16)B_BENDIAN_TO_HOST_INT16(cmd->length));
+#endif
+
+			status = periph_safe_exec(device, request);
+
+			// peripheral layer only creates "read" error
+			if (status == B_DEV_READ_ERROR)
+				return B_DEV_WRITE_ERROR;
+			else if (status != B_OK)
+				return status;
+
+			*trimmedBlocks += trimLength;
+			length -= trimLength;
+			lba += trimLength;
+		}
+	}
+
+	return status;
+}
+
+
+status_t
+periph_trim_device(scsi_periph_device_info* device, scsi_ccb* request,
+	scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks)
+{
+	*trimmedBlocks = 0;
+
+	if (device->unmap_command == TRIM_NONE
+		|| device->max_unmap_lba_count == 0
+		|| device->max_unmap_descriptor_count == 0)
+		return B_UNSUPPORTED;
+
+	switch (device->unmap_command) {
+		case TRIM_UNMAP:
+			return trim_unmap(device, request, ranges, rangeCount,
+				trimmedBlocks);
+		case TRIM_WRITESAME16:
+			return trim_writesame16(device, request, ranges, rangeCount,
+				trimmedBlocks);
+		case TRIM_WRITESAME10:
+			return trim_writesame10(device, request, ranges, rangeCount,
+				trimmedBlocks);
+		default:
+			return B_UNSUPPORTED;
+	}
+}
diff --git a/src/add-ons/kernel/generic/scsi_periph/device.cpp b/src/add-ons/kernel/generic/scsi_periph/device.cpp
index 5d8ab33055..c6bcb83c07 100644
--- a/src/add-ons/kernel/generic/scsi_periph/device.cpp
+++ b/src/add-ons/kernel/generic/scsi_periph/device.cpp
@@ -81,6 +81,9 @@ periph_register_device(periph_device_cookie periph_device,
 	device->next_tag_action = 0;
 	device->preferred_ccb_size = preferredCcbSize;
 	device->rw10_enabled = true;
+	device->unmap_command = TRIM_NONE;
+	device->max_unmap_lba_count = 0;
+	device->max_unmap_descriptor_count = 0;
 
 	// launch sync daemon
 	status_t status = register_kernel_daemon(periph_sync_queue_daemon, device,
diff --git a/src/add-ons/kernel/generic/scsi_periph/io.cpp b/src/add-ons/kernel/generic/scsi_periph/io.cpp
index f3d8bcdc1a..6bce83f90d 100644
--- a/src/add-ons/kernel/generic/scsi_periph/io.cpp
+++ b/src/add-ons/kernel/generic/scsi_periph/io.cpp
@@ -46,64 +46,67 @@ inquiry(scsi_periph_device_info *device, scsi_inquiry *inquiry)
 
 
 static status_t
-vpd_page_inquiry(scsi_periph_device_info *device, uint8 page, void* data,
-	uint16 length)
+vpd_page_inquiry(scsi_periph_device_info* device, scsi_ccb* ccb,
+	uint8 page, void* data, uint16 length)
 {
 	SHOW_FLOW0(0, "");
 
-	scsi_ccb* ccb = device->scsi->alloc_ccb(device->scsi_device);
-	if (ccb == NULL)
-		return B_NO_MEMORY;
-
-	scsi_cmd_inquiry *cmd = (scsi_cmd_inquiry *)ccb->cdb;
+	scsi_cmd_inquiry* cmd = (scsi_cmd_inquiry*)ccb->cdb;
 	memset(cmd, 0, sizeof(scsi_cmd_inquiry));
 	cmd->opcode = SCSI_OP_INQUIRY;
 	cmd->lun = ccb->target_lun;
 	cmd->evpd = 1;
 	cmd->page_code = page;
+	// the scsi_cmd_inquiry structure follows an older SCSI standard
+	// which uses only 8 bits for allocation_length
+	if (length > UINT8_MAX)
+		return EINVAL;
 	cmd->allocation_length = length;
 
 	ccb->flags = SCSI_DIR_IN;
 	ccb->cdb_length = sizeof(scsi_cmd_inquiry);
-
 	ccb->sort = -1;
 	ccb->timeout = device->std_timeout;
 
 	ccb->data = (uint8*)data;
-	ccb->sg_list = NULL;
 	ccb->data_length = length;
+	ccb->sg_list = NULL;
 
-	status_t status = periph_safe_exec(device, ccb);
-
-	device->scsi->free_ccb(ccb);
-
-	return status;
+	return periph_safe_exec(device, ccb);
 }
 
 
 status_t
-vpd_page_get(scsi_periph_device_info *device, uint8 page, void* data,
-	uint16 length)
+vpd_page_get(scsi_periph_device_info* device, scsi_ccb* request,
+	uint8 page, void* data, uint16 length)
 {
 	SHOW_FLOW0(0, "");
 
-	status_t status = vpd_page_inquiry(device, 0, data, length);
+	if (page == SCSI_PAGE_SUPPORTED_VPD)
+		return vpd_page_inquiry(device, request, page, data, length);
+
+	const uint16 bufferLength = 252;
+		// maximum word-aligned value that fits in a byte,
+		// theoretical maximum is offsetof(scsi_page_list, pages) + UINT8_MAX;
+	uint8 buffer[bufferLength];
+	scsi_page_list* vpdPage = (scsi_page_list*)buffer;
+	memset(vpdPage, 0, bufferLength);
+
+	status_t status = vpd_page_inquiry(device, request,
+		SCSI_PAGE_SUPPORTED_VPD, vpdPage, bufferLength);
 	if (status != B_OK)
-		return status; // or B_BAD_VALUE
+		return status;
 
-	if (page == 0)
-		return B_OK;
+	if (vpdPage->page_code != SCSI_PAGE_SUPPORTED_VPD)
+		return B_ERROR;
 
-	scsi_page_list *list_data = (scsi_page_list*)data;
-	int page_length = min_c(list_data->page_length, length -
-		offsetof(scsi_page_list, pages));
-	for (int i = 0; i < page_length; i++) {
-		if (list_data->pages[i] == page)
-			return vpd_page_inquiry(device, page, data, length);
+	uint16 pageLength = min_c(vpdPage->page_length,
+		bufferLength - offsetof(scsi_page_list, pages));
+	for (uint16 i = 0; i < pageLength; i++) {
+		if (vpdPage->pages[i] == page)
+			return vpd_page_inquiry(device, request, page, data, length);
 	}
 
-	// TODO buffer might be not big enough
-
 	return B_BAD_VALUE;
 }
 
diff --git a/src/add-ons/kernel/generic/scsi_periph/scsi_periph_int.h b/src/add-ons/kernel/generic/scsi_periph/scsi_periph_int.h
index 29e4ba6d51..8a25e1f5b9 100644
--- a/src/add-ons/kernel/generic/scsi_periph/scsi_periph_int.h
+++ b/src/add-ons/kernel/generic/scsi_periph/scsi_periph_int.h
@@ -16,6 +16,14 @@
 #include "wrapper.h"
 
 
+enum trim_command {
+	TRIM_NONE,			// TRIM operation is disabled for this device
+	TRIM_UNMAP,			// UNMAP command wil be used
+	TRIM_WRITESAME10,	// WRITE SAME (10) with UNMAP bit enabled will be used
+	TRIM_WRITESAME16	// WRITE SAME (16) with UNMAP bit enabled will be used
+};
+
+
 typedef struct scsi_periph_device_info {
 	struct scsi_periph_handle_info *handles;
 
@@ -28,6 +36,10 @@ typedef struct scsi_periph_device_info {
 
 	bool removable;			// true, if device is removable
 
+	enum trim_command unmap_command;	// command to be used to discard free blocks
+	uint32 max_unmap_lba_count;			// max. number of LBAs in one command
+	uint32 max_unmap_descriptor_count;	// max. number of ranges in one command
+
 	uint32 block_size;
 	int32 preferred_ccb_size;
 	int32 rw10_enabled;		// 10 byte r/w commands supported; access must be atomic
@@ -78,7 +90,7 @@ status_t periph_handle_free(scsi_periph_handle_info *handle);
 
 status_t periph_check_capacity(scsi_periph_device_info *device, scsi_ccb *ccb);
 status_t periph_trim_device(scsi_periph_device_info *device, scsi_ccb *request,
-	scsi_block_range* ranges, uint32 rangeCount);
+	scsi_block_range* ranges, uint32 rangeCount, uint64* trimmedBlocks);
 
 
 // device.c
@@ -101,8 +113,8 @@ status_t periph_io(scsi_periph_device_info* device, io_operation* operation,
 status_t periph_ioctl(scsi_periph_handle_info *handle, int op,
 	void *buf, size_t len);
 void periph_sync_queue_daemon(void *arg, int iteration);
-status_t vpd_page_get(scsi_periph_device_info *device, uint8 page, void* data,
-	uint16 length);
+status_t vpd_page_get(scsi_periph_device_info *device, scsi_ccb* request,
+	uint8 page, void* data, uint16 length);
 
 
 // scsi_periph.c