[PATCH v2] ASoC: core: clarify the driver name initialization

[Pierre-Louis Bossart]

Hi Jaroslav,

>>> The driver field in the struct snd_ctl_card_info is a valid
>>> user space identifier. Actually, many ASoC drivers do not care
>>> and let to initialize this field using a standard wrapping method.
>>> Unfortunately, in this way, this field becomes unusable and
>>> unreadable for the drivers with longer card names. Also,
>>> there is a possibility to have clashes (driver field has
>>> only limit of 15 characters).
>>>
>>> This change will print an error when the wrapping is used.
>>> The developers of the affected drivers should fix the problem.
>>
>> How should we fix this problem?
>>
>> I see all kinds of errors thrown in our first CI results based on
>> 6.1-rc1:
>>
>> [   12.684893] kernel: cml_rt1011_rt5682 cml_rt1011_rt5682: ASoC: driver
>> name too long 'sof-cml_rt1011_rt5682' -> 'sof-cml_rt1011_'
>>
>> [   12.219660] kernel: bxt_da7219_max98357a glk_da7219_mx98357a: ASoC:
>> driver name too long 'sof-glkda7219max' -> 'sof-glkda7219ma'
>>
>> I have no idea what is expected here in terms of naming. It's far from
>> obvious to respect the 15-character limit AND have something
>> readable/sensible given the proliferation of hardware skews.
>>
>> Any suggestions?
> 
> The question is, how deep the driver name should describe the hardware
> details. The two drivers covering the majority hardware use "HDA-Intel"
> and "USB-Audio" strings here and there are a lot of variants of the
> codec / user space devices / mixer controls. The codec chain and
> eventually the audio bridge can be described in other identification
> strings like card components or the card name (note that most end users
> are not able to identify the references to hardware - it's a GUI string).
> 
> I would use "SOF-Intel-CML" and "SOF-Intel-GLK" strings or just
> "SOF-Intel" or any other variant as you like (lower case etc.). My
> opinion is that it's not necessary to have an unique string per driver
> here (the drivers should have just something common like the SOF core
> code).

ok, adding 'SOF-Intel' would be fine, but remind me again how to set
the driver name?

We already set the card name to e.g.
	broxton_audio_card.name = "glkda7219max";
then the sof-prefix gets added, and that's what we use for UCM [1]

how would I modify the driver name?

If I just go ahead and set .driver_name = "SOF-Intel" in the card
declaration, isn't this going to impact the calls to

	soc_setup_card_name(card, card->snd_card->shortname,
			    card->name, NULL);
	soc_setup_card_name(card, card->snd_card->longname,
			    card->long_name, card->name);
	soc_setup_card_name(card, card->snd_card->driver,
			    card->driver_name, card->name);


#define soc_setup_card_name(card, name, name1, name2) \
	__soc_setup_card_name(card, name, sizeof(name), name1, name2)
static void __soc_setup_card_name(struct snd_soc_card *card,
				  char *name, int len,
				  const char *name1, const char *name2)
{
	const char *src = name1 ? name1 : name2;
	int i;

	snprintf(name, len, "%s", src);

	if (name != card->snd_card->driver)
		return;

so the shortname and longname would never be used?

I am beyond confused on all this :-)


[1]
https://github.com/alsa-project/alsa-ucm-conf/tree/master/ucm2/Intel/sof-glkda7219max