dev_printk output

[Matthew Wilcox <matthew@wil.cx>]

On Thu, May 18, 2006 at 01:09:57PM -0700, Patrick Mansfield wrote:
> Funky how loading sd after sg changes the output ... and using the driver
> name as a prefix sometimes messes this up for scsi.
> 
> i.e. scan without sd_mod or sg loaded (and distro I'm using loads sg
> before sd_mod via udev rules):
> 
>  0:0:0:0: Attached scsi generic sg0 type 0
>  0:0:0:1: Attached scsi generic sg1 type 0
> 
> Then remove/add those devices, and sg lines become:
> 
> sd 1:0:0:0: Attached scsi generic sg0 type 0
> sd 1:0:0:1: Attached scsi generic sg1 type 0

I find that a bit confusing too.  Obviously, we should distinguish
different kinds of bus_id from each other somehow -- but isn't the
obvious thing to use the bus name?  That must already be unique as sysfs
relies on it.  ie this patch:

(seems that dev->bus isn't always set; I got a null ptr dereference when
booting without that check).

Signed-off-by: Matthew Wilcox <matthew@wil.cx>

Index: include/linux/device.h
===================================================================
RCS file: /var/cvs/linux-2.6/include/linux/device.h,v
retrieving revision 1.25
diff -u -p -r1.25 device.h
--- include/linux/device.h	13 May 2006 04:12:30 -0000	1.25
+++ include/linux/device.h	19 May 2006 19:54:04 -0000
@@ -412,7 +412,7 @@ extern void firmware_unregister(struct s
 
 /* debugging and troubleshooting/diagnostic helpers. */
 #define dev_printk(level, dev, format, arg...)	\
-	printk(level "%s %s: " format , (dev)->driver ? (dev)->driver->name : "" , (dev)->bus_id , ## arg)
+	printk(level "%s %s: " format , (dev)->bus ? (dev)->bus->name : "", (dev)->bus_id , ## arg)
 
 #ifdef DEBUG
 #define dev_dbg(dev, format, arg...)		\