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

[Pierre-Louis Bossart]

>>> 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.