[PATCH v3] serial: 8250: Report which option to enable for blacklisted PCI devices

["Maciej W. Rozycki" <macro@orcam.me.uk>]

Provide information in the kernel log as to what configuration option to 
enable for PCI UART devices that have been blacklisted in the generic 
PCI 8250 UART driver and which have a dedicated driver available to 
handle that has been disabled.  The rationale is there is no easy way 
for the user to map a specific PCI vendor:device pair to an individual 
dedicated driver while the generic driver has this information readily 
available and it will likely be confusing that the generic driver does 
not register such a port.

This is unlike usual drivers, such as drivers/net/ethernet/3com/3c59x.c 
which handles all the hardware family members regardless of differences 
between them, and following an existing example where a serio driver 
provides suggestions as to the correct configuration options to use:

psmouse serio1: synaptics: The touchpad can support a better bus than the too old PS/2 protocol. Make sure MOUSE_PS2_SYNAPTICS_SMBUS and RMI4_SMB are enabled to get a better touchpad experience.

A message is then printed like:

serial 0000:04:00.3: ignoring port, enable SERIAL_8250_PERICOM to handle

when an affected device is encountered and the generic driver rejects it.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
Changes from v2:

- Include examples of current practices in the change description so as to 
  give a better justification.

Changes from v1:

- Add missing filler struct member initialisers for PCI_DEVICE entries.
---
 drivers/tty/serial/8250/8250_pci.c |   67 ++++++++++++++++++++++---------------
 1 file changed, 40 insertions(+), 27 deletions(-)

linux-serial-8250-pci-blacklist-config.diff
Index: linux-macro/drivers/tty/serial/8250/8250_pci.c
===================================================================
--- linux-macro.orig/drivers/tty/serial/8250/8250_pci.c
+++ linux-macro/drivers/tty/serial/8250/8250_pci.c
@@ -3518,6 +3518,12 @@ static struct pciserial_board pci_boards
 	},
 };
 
+#define REPORT_CONFIG(option) \
+	(IS_ENABLED(CONFIG_##option) ? 0 : (kernel_ulong_t)&#option)
+#define REPORT_8250_CONFIG(option) \
+	(IS_ENABLED(CONFIG_SERIAL_8250_##option) ? \
+	 0 : (kernel_ulong_t)&"SERIAL_8250_"#option)
+
 static const struct pci_device_id blacklist[] = {
 	/* softmodems */
 	{ PCI_VDEVICE(AL, 0x5457), }, /* ALi Corporation M5457 AC'97 Modem */
@@ -3525,40 +3531,43 @@ static const struct pci_device_id blackl
 	{ PCI_DEVICE(0x1543, 0x3052), }, /* Si3052-based modem, default IDs */
 
 	/* multi-io cards handled by parport_serial */
-	{ PCI_DEVICE(0x4348, 0x7053), }, /* WCH CH353 2S1P */
-	{ PCI_DEVICE(0x4348, 0x5053), }, /* WCH CH353 1S1P */
-	{ PCI_DEVICE(0x1c00, 0x3250), }, /* WCH CH382 2S1P */
+	/* WCH CH353 2S1P */
+	{ PCI_DEVICE(0x4348, 0x7053), 0, 0, REPORT_CONFIG(PARPORT_SERIAL), },
+	/* WCH CH353 1S1P */
+	{ PCI_DEVICE(0x4348, 0x5053), 0, 0, REPORT_CONFIG(PARPORT_SERIAL), },
+	/* WCH CH382 2S1P */
+	{ PCI_DEVICE(0x1c00, 0x3250), 0, 0, REPORT_CONFIG(PARPORT_SERIAL), },
 
 	/* Intel platforms with MID UART */
-	{ PCI_VDEVICE(INTEL, 0x081b), },
-	{ PCI_VDEVICE(INTEL, 0x081c), },
-	{ PCI_VDEVICE(INTEL, 0x081d), },
-	{ PCI_VDEVICE(INTEL, 0x1191), },
-	{ PCI_VDEVICE(INTEL, 0x18d8), },
-	{ PCI_VDEVICE(INTEL, 0x19d8), },
+	{ PCI_VDEVICE(INTEL, 0x081b), REPORT_8250_CONFIG(MID), },
+	{ PCI_VDEVICE(INTEL, 0x081c), REPORT_8250_CONFIG(MID), },
+	{ PCI_VDEVICE(INTEL, 0x081d), REPORT_8250_CONFIG(MID), },
+	{ PCI_VDEVICE(INTEL, 0x1191), REPORT_8250_CONFIG(MID), },
+	{ PCI_VDEVICE(INTEL, 0x18d8), REPORT_8250_CONFIG(MID), },
+	{ PCI_VDEVICE(INTEL, 0x19d8), REPORT_8250_CONFIG(MID), },
 
 	/* Intel platforms with DesignWare UART */
-	{ PCI_VDEVICE(INTEL, 0x0936), },
-	{ PCI_VDEVICE(INTEL, 0x0f0a), },
-	{ PCI_VDEVICE(INTEL, 0x0f0c), },
-	{ PCI_VDEVICE(INTEL, 0x228a), },
-	{ PCI_VDEVICE(INTEL, 0x228c), },
-	{ PCI_VDEVICE(INTEL, 0x4b96), },
-	{ PCI_VDEVICE(INTEL, 0x4b97), },
-	{ PCI_VDEVICE(INTEL, 0x4b98), },
-	{ PCI_VDEVICE(INTEL, 0x4b99), },
-	{ PCI_VDEVICE(INTEL, 0x4b9a), },
-	{ PCI_VDEVICE(INTEL, 0x4b9b), },
-	{ PCI_VDEVICE(INTEL, 0x9ce3), },
-	{ PCI_VDEVICE(INTEL, 0x9ce4), },
+	{ PCI_VDEVICE(INTEL, 0x0936), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x0f0a), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x0f0c), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x228a), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x228c), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b96), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b97), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b98), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b99), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b9a), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x4b9b), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x9ce3), REPORT_8250_CONFIG(LPSS), },
+	{ PCI_VDEVICE(INTEL, 0x9ce4), REPORT_8250_CONFIG(LPSS), },
 
 	/* Exar devices */
-	{ PCI_VDEVICE(EXAR, PCI_ANY_ID), },
-	{ PCI_VDEVICE(COMMTECH, PCI_ANY_ID), },
+	{ PCI_VDEVICE(EXAR, PCI_ANY_ID), REPORT_8250_CONFIG(EXAR), },
+	{ PCI_VDEVICE(COMMTECH, PCI_ANY_ID), REPORT_8250_CONFIG(EXAR), },
 
 	/* Pericom devices */
-	{ PCI_VDEVICE(PERICOM, PCI_ANY_ID), },
-	{ PCI_VDEVICE(ACCESSIO, PCI_ANY_ID), },
+	{ PCI_VDEVICE(PERICOM, PCI_ANY_ID), REPORT_8250_CONFIG(PERICOM), },
+	{ PCI_VDEVICE(ACCESSIO, PCI_ANY_ID), REPORT_8250_CONFIG(PERICOM), },
 
 	/* End of the black list */
 	{ }
@@ -3840,8 +3849,12 @@ pciserial_init_one(struct pci_dev *dev,
 	board = &pci_boards[ent->driver_data];
 
 	exclude = pci_match_id(blacklist, dev);
-	if (exclude)
+	if (exclude) {
+		if (exclude->driver_data)
+			pci_warn(dev, "ignoring port, enable %s to handle\n",
+				 (const char *)exclude->driver_data);
 		return -ENODEV;
+	}
 
 	rc = pcim_enable_device(dev);
 	pci_save_state(dev);