On 2011-06-16 17:02, Takashi Iwai wrote:
At Thu, 16 Jun 2011 16:55:39 +0200,
Kay Sievers wrote:
On Thu, Jun 16, 2011 at 16:48, Takashi Iwai<tiwai@xxxxxxx> wrote:
At Thu, 16 Jun 2011 16:28:08 +0200,
Kay Sievers wrote:
On Thu, Jun 16, 2011 at 16:12, David Henningsson
<david.henningsson@xxxxxxxxxxxxx> wrote:
One missing piece for userspace (PulseAudio etc) to actually be able to use
the jack input devices that ALSA create, is that these devices are
accessible by root only. This patch makes the input device nodes accessible
by the same users that can access the sound card: the current logged in
user, as well as users in the audio group.
One thing I was thinking about, was that the udev-acl rule actually grants
read-write access to the input device node, where probably only read access
is needed. Is this dangerous?
Takashi, wasn't there already something else to use from ALSA than the
artificial input devices?
These input devices are just notification from the sound driver at
jack plugging, so basically it's read-only indeed, and setting the
file permission RO would make sense.
So the problem is that there is no way to accomplish that in
70-acl.rules right now. Would it be some kind of security flaw if we
allowed write access? What can you really do/damage by writing to these
things?
Na, I mean, I remember you talking about some other channel of
notifications about jack changes.
Ah, yeah, it's still possible to implement via ALSA control API, too.
Just add a new control element for jack notification, and the apps can
listen to it via normal ALSA API like the mixer elements.
Didn't the input devices get replaced by something on the control
device? Or was that just a plan?
I had some patches for it years ago, but never got merged.
If apps prefer it, I can revisit it. Meanwhile, the jack-input stuff
is already present, so it might not be worth for it.
As for which architecture works better, I'm not sure. Anyway, my point
is, as this is what ALSA currently uses, this is what we should support
all the way up the stack. If ALSA switches architecture, let's revisit
this patch at that point. (Btw, there are already an experimental set of
patches available for PulseAudio that polls for these input events.)
--
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic
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