From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Date: Wed, 01 Aug 2007 22:22:56 +0000 Subject: Re: work-around for video4linux sysfs Message-Id: <20070801222256.GC9617@outflux.net> List-Id: References: <20070731195136.GW9881@outflux.net> In-Reply-To: <20070731195136.GW9881@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Wed, Aug 01, 2007 at 02:58:35PM -0700, Greg KH wrote: > On Wed, Aug 01, 2007 at 02:31:30PM -0700, Kees Cook wrote: > > Is the idea of /dev/v4l/by-path/... sane? Once v4l sysfs was fixed, > > it seems that to support this symlink, the path_id tool would still need > > at least the second patch hunk. Is this correct? > > Probably, and yes, the v4l by-path stuff is a good idea, I'm not trying > to keep that from happening. But are there ids on these devices you can > use too, to get a "by-id" path as well? Do the USB or PCI devices have > a serial number associated with them? If there are serial numbers, the v4l sub-drivers aren't fetching them, or I'm too dense to find them. This is basically why I opted for the by-path symlinks, since nothing else looked like a reasonable unique string. I had originally hoped to build one using something like: $driver_name-$device_type_name-$driver_init_order For example, if I had 2 ivtv devices, and one bttv device, I'd expect to see something like: ivtv-pvr250-0 ivtv-pvr500-1 bttv-thingy-0 But the v4l drivers don't have a common string for the "device_type_name" in my example. (They have a long description string that is usually truncated, but whose layout isn't common between drivers.) While ivtv internally knows about ivtv0 and ivtv1, there doesn't seem to be a way to query a v4l driver about which sub-instance it is. This might be another nice thing to plumb into sysfs, but I imagine it would be needed for each v4l driver. In the 3 example devices above, ivtv0 always inits before ivtv1 in the same order, but bttv may come before ivtv, swapping the video0, video1, video2 devices all over the place. > > By my estimation, the v4l sysfs is missing a "driver" linkage? I'm not > > entirely sure where to start looking. > > What does the v4l device sysfs directory tree look like? Is the > "driver" link the only thing you are missing to do this in an easier > manner in your script? I think if that was in there, it would at least solve the current gross need to cd into the directory to pull a PWD. :) There may still be a need to append the driver name to the path-id output, but I suspect that would be simple to do in the already-needed second hunk of the patch. -- Kees Cook @outflux.net ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel