serial: 8250_exar: Bug fix for determination of number of ports for Commtech PCIe cards

serial: 8250_exar: Bug fix for determination of number of ports for Commtech PCIe cards

The following line is used to determine the number of ports for each exar board in a/drivers/tty/serial/8250/8250_exar.c:589

nr_ports = board->num_ports ? board->num_ports : pcidev->device & 0x0f;

If the number of ports a card has is not explicitly specified, it defaults to the rightmost 4 bits of the PCI device ID. This is prone to error since not all PCI device IDs contain a number which corresponds to the number of ports that card provides.

This particular case involves COMMTECH_4224PCIE and COMMTECH_4228PCIE cards with device ID 0x0020 and 0x0021. Currently the multiport cards receive 0 and 1 port instead of 4 and 8 ports respectively.

To fix this, each Commtech Fastcom PCIe card is given a struct where the number of ports is explicitly specified. This ensures 'board->num_ports' is used instead of the default 'pcidev->device & 0x0f'.

---
Thank you,
Valmer Huhn

index ddb6aeb76dc5..793906afb0f6 100644
@@ -734,6 +734,24 @@ static const struct exar8250_board pbn_exar_XR17V35x = {
 	.exit		= pci_xr17v35x_exit,
 };
 
+static const struct exar8250_board pbn_fastcom_XR17V352 = {
+	.num_ports	= 2,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
+static const struct exar8250_board pbn_fastcom_XR17V354 = {
+	.num_ports	= 4,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
+static const struct exar8250_board pbn_fastcom_XR17V358 = {
+	.num_ports	= 8,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
 static const struct exar8250_board pbn_exar_XR17V4358 = {
 	.num_ports	= 12,
 	.setup		= pci_xr17v35x_setup,

@@ -801,9 +819,9 @@ static const struct pci_device_id exar_pci_tbl[] = {
 	EXAR_DEVICE(EXAR, XR17V358, pbn_exar_XR17V35x),
 	EXAR_DEVICE(EXAR, XR17V4358, pbn_exar_XR17V4358),
 	EXAR_DEVICE(EXAR, XR17V8358, pbn_exar_XR17V8358),
-	EXAR_DEVICE(COMMTECH, 4222PCIE, pbn_exar_XR17V35x),
-	EXAR_DEVICE(COMMTECH, 4224PCIE, pbn_exar_XR17V35x),
-	EXAR_DEVICE(COMMTECH, 4228PCIE, pbn_exar_XR17V35x),
+	EXAR_DEVICE(COMMTECH, 4222PCIE, pbn_fastcom_XR17V352),
+	EXAR_DEVICE(COMMTECH, 4224PCIE, pbn_fastcom_XR17V354),
+	EXAR_DEVICE(COMMTECH, 4228PCIE, pbn_fastcom_XR17V358),
 
 	EXAR_DEVICE(COMMTECH, 4222PCI335, pbn_fastcom335_2),
 	EXAR_DEVICE(COMMTECH, 4224PCI335, pbn_fastcom335_4),

On Wed, Aug 12, 2020 at 05:49:37PM -0400, Valmer Huhn wrote:

Thanks for the report. It needs a slight corrections I tell about below.

This should not be present in the body.
And in the subject it would be better to reduce the text to something like

serial: 8250_exar: Fix number of ports for Commtech PCIe cards

There is no a/ folder and we don't need the full path anyway, just something like '8250_exar.c line 589' is enough.

Also refer to Exar with capitalized name.

'...with device IDs 0x0020, 0x0021 and 0x0022.'

and update this accordingly.

Please, add a Fixes tag.

...

With Best Regards,
Andy Shevchenko

Thank you very much for your feedback.

I will resubmit the patch with this subject line and include the changes you suggested.

Thank you,
Valmer Huhn