On Tue, 14 Jan 2020 10:48:24 +0100, jeff_chang(張世佳) wrote:

Dear Takashi:

Thank for your replying.

1.> +static int mt6660_component_get_volsw(struct snd_kcontrol *kcontrol,

...

• struct snd_ctl_elem_value *ucontrol) {

+struct snd_soc_component *component = +snd_soc_kcontrol_component(kcontrol); +struct mt6660_chip *chip = (struct mt6660_chip *) +snd_soc_component_get_drvdata(component); +int ret = -EINVAL;

+if (!strcmp(kcontrol->id.name, "Chip Rev")) { +ucontrol->value.integer.value[0] = chip->chip_rev & 0x0f; +ret = 0; +} +return ret;

So, "T0 SEL" control gets always an error when reading? Then can't we pass simply NULL for get ops instead?

Jeff : T0 SEL use snd_soc_get_volsw, it will not use this function.

Then what's the reason of this hackish check?

2. So here both 24 and 32 bits data are handled equally, and...

....

...

+ret = snd_soc_component_update_bits(dai->component, +MT6660_REG_TDM_CFG3, 0x3f0, word_len << 4);

... word_len is same for both S32 and S24 formats, so there can be no difference between S24 and S32 format handling in the code. Meanwhile, the supported formats are:

...

+#define STUB_FORMATS(SNDRV_PCM_FMTBIT_S16_LE | \ +SNDRV_PCM_FMTBIT_U16_LE | \ +SNDRV_PCM_FMTBIT_S24_LE | \ +SNDRV_PCM_FMTBIT_U24_LE | \ +SNDRV_PCM_FMTBIT_S32_LE | \ +SNDRV_PCM_FMTBIT_U32_LE)

Are you sure that S24_* formats really work properly?

Also, the code has no check / setup of the format signedness. Do unsigned formats (U16, U24, etc) really work as expected, too?

Jeff : Yes, it works.

So, for the codec, it doesn't matter at all about the signedness and the alingment of 32bit / 24bit of the incoming signals, but magically handled as is? Interesting...

thanks,

Takashi