Re: [PATCH] Fix serial_match_port() for dynamic major tty-device numbers

On Tue, 24 Jun 2008, Andrew Morton wrote:

On Sun, 22 Jun 2008 00:45:25 +0200 (CEST)
Guennadi Liakhovetski [off-list ref] wrote:

quoted

As reported by Vipul Gandhi, the current serial_match_port() doesn't work 
for tty-devices using dynamic major number allocation. Fix it.

Signed-off-by: Guennadi Liakhovetski <redacted>
Tested-by: Vipul Gandhi <redacted>

---

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 0f5a179..593ae85 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c

@@ -1949,7 +1949,9 @@ struct uart_match {
 static int serial_match_port(struct device *dev, void *data)
 {
 	struct uart_match *match = data;
-	dev_t devt = MKDEV(match->driver->major, match->driver->minor) + match->port->line;
+	struct tty_driver *tty_drv = match->driver->tty_driver;
+	dev_t devt = MKDEV(tty_drv->major, tty_drv->minor_start) +
+		match->port->line;
 
 	return dev->devt == devt; /* Actually, only one tty per port */

Well that sounds bad.  We need to work out whether this fix is needed
in 2.6.25 and possibly eariler.

Not earlier, this code is only there since 2.6.25.

What are the consequences of this error?

It Oopses, if you suspend a serial port with _dynamic_ major number. ATM, 
I think, there's only the drivers/serial/jsm/jsm_driver.c driver, that 
does it in-tree.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer