On Tue, 21 Oct 2008, Larry on the Dell wrote:
> > My happauge PVR-USB2 wants to default to television input rather than my > preferred s-video. So I read cur_val could be written to control this. > So working my in > > [EMAIL PROTECTED]:/sys/class/pvrusb2/sn-8504958/ctl_input$ cd > /sys/class/pvrusb2/sn-8504958/ctl_input > [EMAIL PROTECTED]:/sys/class/pvrusb2/sn-8504958/ctl_input$ ls -al > total 0 > drwxr-xr-x 2 root root 0 2008-10-21 12:35 . > drwxr-xr-x 56 root root 0 2008-10-21 12:33 .. > -rw-rw-r-- 1 root root 4096 2008-10-21 12:35 cur_val > -r--r--r-- 1 root root 4096 2008-10-21 12:35 enum_val > -r--r--r-- 1 root root 4096 2008-10-21 12:35 name > -r--r--r-- 1 root root 4096 2008-10-21 12:35 type > > [EMAIL PROTECTED]:/sys/class/pvrusb2/sn-8504958/ctl_input$ cat cur_val > television > > so I don't want the television input, I want the s-video input. So > attempt to write that > > [EMAIL PROTECTED]:/sys/class/pvrusb2/sn-8504958/ctl_input$ echo s-video > > cur_val > > which results in > > -bash: cur_val: Permission denied > > so I tried > > [EMAIL PROTECTED]:/sys/class/pvrusb2/sn-8504958/ctl_input$ sudo echo > s-video > > cur_val > > with the same result. > > -bash: cur_val: Permission denied > > This is with mythbuntu and > MythTV Version : 18207 > MythTV Branch : branches/release-0-21-fixes > Library API : 0.21.20080304-1 > > > From the command line, how do I set ctl_imput to s-video? > You have to be root in order to do that. The sudo trick should have worked, but maybe your distro is doing something strange with sudo? Try using "sudo -s" to get a root shell. Then you can at least verify that you really are root. (And also once you're in the shell you can try to directly modify those sysfs nodes.) As for why you need to be root, there isn't much the driver can do about that. From the viewpoint of inside the kernel there really isn't a way to change the owner of those sysfs files. The permissions can be adjusted, but it's unwise for those fields to be world-writeable - since then anything can take over control of the device. With device control, usually one changes the gid of the files to match a specific group (e.g. "video") and then users with permission to operate the device need only be associated with that group. But even there the driver can't do anything even if it wanted to, since the actual integer gid value for, say, "video" is distro-specific. One clean, theoretical, way to fix this is for there to be a udev rule that executes a chgrp on all of /sys/class/pvrusb2/sn-xxxxxx at the point when the device appears. That has the additional advantage that udev can know the correct distro-specific gid value to use. But I haven't implemented this (this is a task really outside of the driver). But it would be a useful exercrise for someone else to set up. -Mike -- Mike Isely isely @ pobox (dot) com PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8 _______________________________________________ pvrusb2 mailing list [email protected] http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2
