[516] in linux-scsi channel archive
Selectable Generic SCSI device
daemon@ATHENA.MIT.EDU (Brit Systems)
Wed Aug 16 06:25:43 1995
Date: Tue, 15 Aug 1995 16:54:32 -0500 (CDT)
From: Brit Systems <brit@metronet.com>
To: linux-scsi@vger.rutgers.edu
I'm playing with the generic SCSI device. Since some of the devices,
like robotic arms, are kind of slow, I wanted to use select to tell
me when the SCSI command has completed.
I tried to write a command to the sg device, then do a select on it
to wait for it to become ready to read, then I read the device.
It appears that the select will return immediately. Sometimes the read
will take a long time after that.
When I open the device with a O_NONBLOCK flag set, the select still
returns immediately but the read will fail with "Try Again". After
several retries, it eventually gets it.
I have not tried poll instead of select.
Does the generic SCSI device not support select or is there a problem
with my system?
If it does not support it, can someone give me an idea how hard it is
to add that kind of support?
Is there some better way that I should try doing this?
BRIT Systems, Medical Imaging
3626 N. Hall Street, Suite 616, Dallas, TX 75219
(214) 528-4446 fax: (214) 528-4916
