[alsa-devel] [PATCH V5 1/2] ASoC: core: add API for registering DMI card names

[Takashi Sakamoto]

On Apt 5 2016 14:38, Takashi Sakamoto wrote:
> Hi,
>
> On Apr 5 2016 13:26, han.lu at intel.com wrote:
>> From: "Lu, Han" <han.lu at intel.com>
>>
>> Add core API for registering DMI card names, so user space utils such
>> as PA and UCM can distinguish various products.
>> Previously on ASoC, the card short name, driver name and long name are
>> all the same as the machine driver name.
>> The patch adds more board information:
>>    card driver name --->  machine driver name
>>    card short name  --->  DMI_BOARD_NAME or DMI_PRODUCT_NAME
>>    card long name and
>>    card component   --->  short name;driver name;(DMI_SYS_VENDOR,
>>                           optional);(the firmware name, optional)
>>
>> Signed-off-by: Lu, Han <han.lu at intel.com>
>>
>> diff --git a/include/sound/soc.h b/include/sound/soc.h
>> index 02b4a21..4e80444 100644
>> --- a/include/sound/soc.h
>> +++ b/include/sound/soc.h
>> @@ -486,6 +486,9 @@ void snd_soc_runtime_deactivate(struct
>> snd_soc_pcm_runtime *rtd, int stream);
>>   int snd_soc_runtime_set_dai_fmt(struct snd_soc_pcm_runtime *rtd,
>>       unsigned int dai_fmt);
>>
>> +int snd_soc_set_card_names(struct snd_soc_card *card, const char *board,
>> +        const char *vendor, const char *firmware);
>> +
>>   /* Utility functions to get clock rates from various things */
>>   int snd_soc_calc_frame_size(int sample_size, int channels, int
>> tdm_slots);
>>   int snd_soc_params_to_frame_size(struct snd_pcm_hw_params *params);
>> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
>> index d2e62b15..a06b9b9 100644
>> --- a/sound/soc/soc-core.c
>> +++ b/sound/soc/soc-core.c
>> @@ -48,6 +48,9 @@
>>
>>   #define NAME_SIZE    32
>>
>> +#define LONGNAME_SIZE    80    /* size of longname[] in struct
>> snd_card */
>> +static char card_longname[LONGNAME_SIZE];
>> +
>
> I'm not a developer for SoC sound interfaces or Skylake something,
> however I wonder the reason to add fiile local variable for this
> purpose. Could I request your intension about it?
>
> Here, I assume a platform with some sound intefaces (I don't know we
> rarely have the situation or not). If several drivers are probed for
> these interfaces, the 'snd_soc_set_card_names()' might cause a race
> condition between the drivers against the local variable. However,
> there's no usage of lock primitive.
> Additionally, when probing processing finishes for the second driver,
> the local variable changes its contents. Then, ALSA core returns the
> renewed string as the component of the first driver. This is not good.

Oops. The additional case comes from my misunderstanding. It never occurs...

So the point is the race condition.

> If it's too rare that a platform with several interfaces, please inform
> it to me.
>
>>   #ifdef CONFIG_DEBUG_FS
>>   struct dentry *snd_soc_debugfs_root;
>>   EXPORT_SYMBOL_GPL(snd_soc_debugfs_root);
>> @@ -1828,6 +1831,70 @@ int snd_soc_runtime_set_dai_fmt(struct
>> snd_soc_pcm_runtime *rtd,
>>   }
>>   EXPORT_SYMBOL_GPL(snd_soc_runtime_set_dai_fmt);
>>
>> +/**
>> + * snd_soc_set_card_names() - Register DMI names to card
>> + * @card: The card to register DMI names
>> + * @board: DMI_BOARD_NAME or DMI_PRODUCT_NAME
>> + * @vendor: DMI_SYS_VENDOR, optional
>> + * @firmware: The firmware name, optional
>> + *
>> + * This function registers DMI names to card for the userspace to
>> distinguish
>> + * different boards/products:
>> + *   card driver name --->  machine driver name
>> + *   card short name  --->  DMI_BOARD_NAME or DMI_PRODUCT_NAME
>> + *   card long name and
>> + *   card component   --->  short name;driver name;(DMI_SYS_VENDOR,
>> optional)
>> + *                          ;(firmware name, optional)
>> + *
>> + * Returns 0 on success, otherwise a negative error code.
>> + */
>> +int snd_soc_set_card_names(struct snd_soc_card *card, const char *board,
>> +        const char *vendor, const char *firmware)
>> +{
>> +    int ret = 0;
>> +    size_t name_size;
>> +
>> +    if (!board) {
>> +        dev_err(card->dev, "ASoC: the board/product name is empty!\n");
>> +        return -EINVAL;
>> +    }
>> +
>> +    /* card driver name */
>> +    card->driver_name = card->name;
>> +
>> +    /* card short name */
>> +    card->name = board;
>> +
>> +    /* card long name */
>> +    name_size = strlen(card->name) + strlen(card->driver_name) + 4;
>> +    if (vendor)
>> +        name_size += strlen(vendor);
>> +    if (firmware)
>> +        name_size += strlen(firmware);
>> +    if (name_size > LONGNAME_SIZE)
>> +        return -ENOMEM;
>> +
>> +    snprintf(card_longname, LONGNAME_SIZE, "%s;%s;",
>> +            card->name, card->driver_name);
>> +    if (vendor)
>> +        strlcat(card_longname, vendor, LONGNAME_SIZE);
>> +    strlcat(card_longname, ";", LONGNAME_SIZE);
>> +    if (firmware)
>> +        strlcat(card_longname, firmware, LONGNAME_SIZE);
>> +
>> +    card->long_name = card_longname;
>> +
>> +    /* card component */
>> +    if (sizeof(card->snd_card->components) < name_size
>> +            + strlen(card->snd_card->components))
>> +        return -ENOMEM;
>> +
>> +    ret = snd_component_add(card->snd_card, card->long_name);
>> +
>> +    return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(snd_soc_set_card_names);
>> +
>>   static int snd_soc_instantiate_card(struct snd_soc_card *card)
>>   {
>>       struct snd_soc_codec *codec;
>
> Regards
>
>
> Takashi Sakamoto