Messages in this thread | | | Subject | Re: sysfs permissions on dynamic attributes (led delay_on and delay_off) | From | Richard Purdie <> | Date | Sat, 21 Jul 2012 12:21:47 +0100 |
| |
On Sat, 2012-07-21 at 01:26 -0700, Colin Cross wrote: > On Sat, Jul 21, 2012 at 12:33 AM, Richard Purdie > <richard.purdie@linuxfoundation.org> wrote: > > On Fri, 2012-07-20 at 21:08 -0700, Greg KH wrote: > >> On Fri, Jul 20, 2012 at 05:46:14PM -0700, Colin Cross wrote: > >> > I'm trying to use the standard ledtrig-timer.c code to handle led > >> > blinking for notifications on an Android device, and I'm hitting some > >> > issues with setting permissions on the dynamically created delay_on > >> > and delay_off attributes. For most sysfs files, we have userspace > >> > uevent parser that watches for device add notifications and > >> > chowns/chmods attributes. This doesn't work for delay_on and > >> > delay_off, because they are created later, when "timer" is written to > >> > the trigger attribute. There is no uevent when the new files are > >> > created, and sysfs doesn't support inotify, so I don't see any way to > >> > receive an event to set the permissions. This issue exists any time > >> > that device_create_file is called after device_add. > >> > > >> > What is the appropriate way to get an event to set the permissions? > >> > Add inotify support for sysfs file creation? Send a KOBJ_CHANGE > >> > uevent in device_create_file? > >> > >> No. > >> > >> > Send a KOBJ_CHANGE uevent from the driver after calling > >> > device_create_file? > >> > >> Yes. > >> > >> > Dynamically create a timer device under /sys/class/leds/<led> so a new > >> > add uevent gets sent? > >> > >> Ick. > >> > >> > Promote blinking to be a core led feature instead of a trigger, so the > >> > files are always present? > >> > >> That's the best thing, why not just do that? > > > > This implies we should make every trigger a core led feature and > > effectively do away with triggers. I'm not sure that makes sense. > > Blinking is already effectively a core feature. It is implemented in > led-core.c so it can be used by other triggers besides timer, it's > state is stored in the led_classdev structure, not in the trigger > data, and the only thing left in ledtrig-timer.c is the sysfs files.
Having the attributes present all the time leads to some nasty questions like how the on/off delays interact with things like say a network activity trigger. Not all triggers are going to respect these delay values and I can imagine a whole new set of nasty bug reports with no easy solutions if this change is made...
Cheers,
Richard
| |