pc_serial: manually probe the default ISA ports

Since config_manager is basically a stub, and even VirtualBox
doesn't publish the serial ports as PCI devices, we must probe for them.

Ideally config_manager would find them in the device manager tree
which would have been populated from the PnP BIOS or even ACPI tables...

src/add-ons/kernel/drivers/ports/pc_serial/Driver.cpp

@@ -151,6 +151,17 @@ static const struct serial_support_descriptor sSupportedDevices[] = {
 };
 
 
+// hardcoded ISA ports
+static struct isa_ports {
+	uint32 ioBase;
+	uint32 irq;
+} sHardcodedPorts[] = {
+	{ 0x3f8, 4 },
+	{ 0x2f8, 3 },
+	{ 0x3e8, 4 },
+	{ 0x2e8, 3 },
+};
+
 #if 0
 status_t
 pc_serial_device_added(pc_device device, void **cookie)
@@ -492,6 +503,30 @@ next_split:
 	return B_OK;
 }
 
+
+// until we support ISA device enumeration from PnP BIOS or ACPI,
+// we have to probe the 4 default COM ports...
+status_t
+scan_isa_hardcoded()
+{
+#ifdef HANDLE_ISA_COM
+	int i;
+
+	//TODO: check and filter out the kernel debug port
+	for (i = 0; i < 4; i++) {
+		SerialDevice *device;
+		device = new(std::nothrow) SerialDevice(&sSupportedDevices[0],
+			sHardcodedPorts[i].ioBase, sHardcodedPorts[i].irq);
+		if (device && device->Probe())
+			pc_serial_insert_device(device);
+		else
+			delete device;
+	}
+#endif
+	return B_OK;
+}
+
+
 // this version doesn't use config_manager, but can't probe the IRQ yet
 status_t
 scan_pci_alt()
@@ -695,14 +730,15 @@ init_driver()
 
 	status = ENOENT;
 
-	scan_bus(B_ISA_BUS);
+	(void)scan_bus;
+	//scan_bus(B_ISA_BUS);
 	//scan_bus(B_PCI_BUS);
+	scan_isa_hardcoded();
 	scan_pci_alt();
 
 	// XXX: ISA cards
 	// XXX: pcmcia
 
-	
 	TRACE_FUNCRET("< init_driver() returns\n");
 	return B_OK;
 

src/add-ons/kernel/drivers/ports/pc_serial/SerialDevice.cpp

@@ -65,6 +65,21 @@ SerialDevice::~SerialDevice()
 }
 
 
+bool
+SerialDevice::Probe()
+{
+	uint8 msr;
+	msr = ReadReg8(MSR);
+	// just in case read twice to make sure the "delta" bits are 0
+	msr = ReadReg8(MSR);
+	// this should be enough to probe for the device for now
+	// we might want to check the scratch reg, and try identifying
+	// the model as in:
+	// http://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Programming#Software_Identification_of_the_UART
+	return (msr != 0xff);
+}
+
+
 status_t
 SerialDevice::Init()
 {

src/add-ons/kernel/drivers/ports/pc_serial/SerialDevice.h

@@ -22,6 +22,8 @@ public:
 									*device, uint32 ioBase, uint32 irq, const SerialDevice *master=NULL);
 virtual							~SerialDevice();
 
+		bool					Probe();
+
 static	SerialDevice *			MakeDevice(struct serial_config_descriptor 
 									*device);