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

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Date:	Wed, 25 Jun 2008 00:54:37 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	vcgandhi1@....com, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: 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 <g.liakhovetski@....de> wrote:
> 
> > 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 <g.liakhovetski@....de>
> > Tested-by: Vipul Gandhi <vcgandhi1@....com>
> > 
> > ---
> > 
> > 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
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