power management in ALSA

power management in ALSA

[Tehn Yit Chin]

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Hi all,

I am trying to put power management awareness into a driver that I wrote,
but I am having a little trouble understanding which model to use.

Looking at the other drivers, I noticed that the suspend/resume callbacks
can be registered via snd_card_set_pm_callback(). The power management is
then handled via pm.c and friends.

The other way is to initialise the suspend/resume callbacks via the linux
device driver model like the following, and then registered via
driver_register(). I think that the power management is then handled by
sysfs.

static struct device_driver codec_driver = {
        .name = "codec",
        .bus = &platform_bus_type,
        .probe = codec_probe,
        .remove = codec_remove,
        .suspend = codec_suspend,
        .resume = codec_resume
};

Any suggestions on which is a better/correct method is welcome.

many thanks,
tyc

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Re: power management in ALSA

[Takashi Iwai]

At Wed, 14 Dec 2005 10:50:05 +1100,
Tehn Yit Chin wrote:
> 
> Hi all,
> 
> I am trying to put power management awareness into a driver that I wrote, but I am
> having a little trouble understanding which model to use.
> 
> Looking at the other drivers, I noticed that the suspend/resume callbacks can be
> registered via snd_card_set_pm_callback(). The power management is then handled via
> pm.c and friends.
> 
> The other way is to initialise the suspend/resume callbacks via the linux device
> driver model like the following, and then registered via driver_register(). I think
> that the power management is then handled by sysfs.
> 
> static struct device_driver codec_driver = {
>         .name = "codec",
>         .bus = &platform_bus_type,
>         .probe = codec_probe,
>         .remove = codec_remove,
>         .suspend = codec_suspend,
>         .resume = codec_resume
> };
> 
> Any suggestions on which is a better/correct method is welcome.

The PM stuff has been completely changed in the recent version.
There is no longer the common PM layer in ALSA (except for
snd_power_change_state()).  Please take a look at ALSA 1.0.11rc1.

BTW, the correct PM implementation is the latter, using suspend/resume
callbacks of corresponding driver structs.


Takashi


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Re: power management in alsa

[Takashi Iwai]

At Wed, 25 Jul 2007 14:36:58 +0200,
Andi Kleen wrote:
> 
> 
> Hallo,
> 
> I noticed ALSA hda seems to only change PCI power management states
> of the sound devices on suspend/resume. Is there a reason the device
> cannot be automatically suspended when nobody has sound opened? 

I made once the automatic power-control patch for hd-audio, but it was
possibly racy and a bit messy implementation, so I abandoned it.
Since then, no one has worked on this issue.


Takashi

power management in alsa

[Andi Kleen]

Hallo,

I noticed ALSA hda seems to only change PCI power management states
of the sound devices on suspend/resume. Is there a reason the device
cannot be automatically suspended when nobody has sound opened? 

-Andi