ASoC driver names

[Pierre-Louis Bossart]

> +#ifdef CONFIG_SND_SOC_DRIVER_NAMES
> +       if (!card->driver_name) {
> +               dev_warn(card->dev,
> +                        "ASoC: Card driver does not set the driver name\n");
> +               return -EINVAL;
> +       }

I am all for Jaroslav's proposal of making the driver name the basis for 
UCM identification. we've been working on this since e.g. the addition 
of the sof- prefix creates a driver name that makes no sense after a 
truncation of the card name to 16 characters [1] [2] - still WIP.

Making the card name more user-friendly is also a good thing, there's 
also a nice hidden feature when the card name contains spaces, the last 
word - typically the codec - is used for the card ID.

But reporting an error when the driver name is not set is a bit extreme 
and would break all Intel boards. I think we want to encourage people to 
move to the suggested solution, but do we want to break existing setups?
I must admit I also don't see a generic solution when the card is 
generated from a DT description, it's not straightforward to translate 
parsed elements into human-readable ones.

While I am at it, I think we should probably avoid using the DMI 
information for the long card name. It's just awful. It might be a 
better idea to add it in the component strings (if it fits) so that UCM 
can use it internally, but it's really horrible. Even with the clean-ups 
suggested by Jaroslav I ended-up with this horror of a long name on my 
test device:

root at Zotac:~# cat /proc/asound/cards
  0 [rt5640         ]: SOF - sof-bytcht rt5640
                       ZOTAC-XXXXXX-XX-CherryTrailFFD

If we really wanted to be user-friendly we'd use something like

"SOF card for Baytrail/Cherrytrail devices with Realtek RT5640 codec"

and apply the same pattern for all machine drivers.

[1] https://github.com/thesofproject/linux/pull/2021

[2] 
https://github.com/alsa-project/alsa-ucm-conf/pull/20/commits/4cc7fe4493c237253cb43cf7d33c32ec975a0691