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

[Pierre-Louis Bossart]

>> No, replacing firmware files is not viable.
>>
>> Let me give you a practical example. In the course of SOF development,
>> we routinely copy new test firmware+topology in the location of
>> distribution-managed files. It's classic that when there is a
>> distribution update in the background to install the latest SOF
>> release, our test files are overwritten and it's not usual for
>> developers to lose time trying to figure out why the functionality
>> changed. We do need to have multiple paths and NEVER override what is
>> provided by the distributions. it's the moral equivalent of /usr/bin
>> v. /usr/local/bin.
> 
> Use /lib/firmware/updates/*.  That precedes over the standard path
> /lib/firmware/*.  (Also /lib/firmware/updates/$VERSION has even higher
> priority.)

thanks for the feedback Takashi, I had no idea this even existed :-)

The documentation is here:
https://www.kernel.org/doc/html/latest/driver-api/firmware/fw_search_path.html

I guess that removes the need for udev rules to select the 
firmware+topology in simple cases, e.g. if you have only one custom 
version or an image overlay.