[PATCH] ALSA: core - add more card sysfs entries

[Jaroslav Kysela]

Dne 08. 04. 21 v 22:01 Jaroslav Kysela napsal(a):
> Dne 08. 04. 21 v 21:41 Pierre-Louis Bossart napsal(a):
>>
>>
>>
>>>>> Yes, I'm talking about rules which depends on the sound driver specific sysfs
>>>>> attributes (you can match the modified /sys/module/*/parameters here).
>>>>
>>>> you lost me with 'match the modified parameters' wording. who matches
>>>> and who modifies those parameters?
>>>
>>> You can probably add something like this to the sound-card.rules:
>>>
>>> SUBSYSTEMS=="pci",ATTR{device/driver/module}=="snd_soc_sof_sdw",
>>>    ATTR{device/driver/module/../snd_sof_pci/parameters/tplg_path}=="intel/sof-tplg/pdm1",
>>>    DO_SOMETHING_HERE
>>>
>>> DO_SOMETHING_HERE may be ATTR{longname}="My Long Name" for example when my change is accepted.
>>
>> Humm, not sure this can work due to dependencies.
>>
>> The machine device is neither an ACPI nor PCI one. It's a platform device.
>>
>> When the PCI device is detected, the PCI core will call the SOF driver 
>> probe, which will first try and boot the firmware, and then create the 
>> platform device. That results in the probe of the machine driver which 
>> creates the card, but that happens *after* booting the firmware.
>>
>> the DSP firmware is setup starting here:
>>
>> https://elixir.bootlin.com/linux/latest/source/sound/soc/sof/core.c#L138
>>
>> and the machine device is created almost last, after registering the 
>> ASoC components.
>>
>> https://elixir.bootlin.com/linux/latest/source/sound/soc/sof/core.c#L234
>>
>> when the card is created, it's too late to change the firmware path or 
>> any firmware-related parameters.
> 
> I just tried to describe the possible 2nd stage - modify the sysfs attributes
> when the card with the modified firmware is created (all modules are loaded
> and initialized). The 1st stage like from Curtis must be retained. It ensures
> to load the right fw.
> 
> SYSTEMS=="pci" checks also parents and card0 links to pci device: card0 ->
> ../../devices/pci0000:00/0000:00:1f.3/sof_sdw/sound/card0 . You can modify
> this matching anyway - the goal is to run commands for the specific driver and
> module parameters when the card is loaded (avoid to change the card attributes
> for other hw).
> 
> I'm not an udev expert, so there may be a bug in my suggestion. I also think
> that the filter may be specified more elegantly (probably using the DRIVER
> match or so).

Another way to use two rules - use internal udev device environment variable
(it seems more straight):

PCI detection level:

SUBSYSTEM=="pci", ATTR{vendor}=="0x8086", ATTR{device}=="0xa0c8",
ATTR{class}=="0x040100",ATTRS{[dmi/id]board_name}=="Eldrid",
ENV{SOUND_SOF_PROFILE}="MyProfile",...module stuff...

Card instance level (sound-card.rules):

SUBSYSTEMS=="pci",ENV{SOUND_SOF_PROFILE}=="MyProfile",...attr setup...

					Jaroslav

-- 
Jaroslav Kysela <perex at perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.