From: Richard Purdie <richard.purdie@linuxfoundation.org>
To: Colin Cross <ccross@android.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
lkml <linux-kernel@vger.kernel.org>,
Bryan Wu <bryan.wu@canonical.com>
Subject: Re: sysfs permissions on dynamic attributes (led delay_on and delay_off)
Date: Sat, 21 Jul 2012 12:21:47 +0100 [thread overview]
Message-ID: <1342869707.21788.50.camel@ted> (raw)
In-Reply-To: <CAMbhsRREVcqf+pnamY62wGcd2mBif8W8_CRXdJQCQvL14Dy3Eg@mail.gmail.com>
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
next prev parent reply other threads:[~2012-07-21 11:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-21 0:46 sysfs permissions on dynamic attributes (led delay_on and delay_off) Colin Cross
2012-07-21 4:08 ` Greg KH
2012-07-21 5:14 ` Colin Cross
2012-07-21 15:07 ` Greg KH
2012-07-21 7:33 ` Richard Purdie
2012-07-21 8:26 ` Colin Cross
2012-07-21 11:21 ` Richard Purdie [this message]
2012-07-21 14:31 ` Henrique de Moraes Holschuh
2012-07-21 15:42 ` Colin Cross
2012-07-21 16:08 ` Henrique de Moraes Holschuh
2012-07-21 16:15 ` Greg KH
2012-07-21 16:23 ` Colin Cross
2012-07-21 16:13 ` Greg KH
2012-07-21 16:22 ` Colin Cross
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