[sane-devel] 'scanimage -L' fails first time with modular SCSI drivers

[Douglas Gilbert]

Henning Meier-Geinitz wrote:
> Hi,
> 
> On Mon, Feb 25, 2002 at 01:30:32PM +0100, Oliver Rauch wrote:
> 
>>Henning Meier-Geinitz wrote:
>>
>>
>>>Is anybody against the following patch?
>>>
>>>+  #define FIND_DEVICES_TOUCH_FILE "/dev/sg0"
>>>
>>
>>May be this should be a list:
>>
>>/dev/sg0, /dev/sga are both relevant for linux,
>>
> 
> Are they really relevant any more? Even the oldest box I could find
> (SuSE system from 1997, kernel 2.0.3x) had only /dev/sg0...7 and no
> /dev/sga etc. I remember that some systems had symlinks sga --> sg0
> but how old are the real sga devices? Newer then /proc/scsi/scsi?

The sg driver internally switched from alphabetical
(e.g. /dev/sga) to numeric (e.g. /dev/sg0) notation
in sg version 2.1.38 which was dated 2000/05/27. That
first appeared in linux kernel 2.2.16 . Prior to that
distributions where already setting up /dev entries
(with mknod) for sg<n> where "n" is numeric.
It shouldn't hurt to probe both.

Just one suggestion: you should open sg devices
O_NONBLOCK when probing lest you hang on some other
application's exclusive lock (e.g. cdrecord). If
a non-blocking open fails with an errno of EBUSY
then leave that device alone.

>>what about /dev/uk0 - are there any modules when uk0 is used?
>>
> 
> Aren't those only used on *BSD? As we are talking about kernel modules
> and /proc/scsi/scsi this looks pretty Linux-only for me.

I don't know where these /dev/uk<n> device names came from.
Any char device name with a major number of 21 is a hook
to the sg driver.

Doug Gilbert