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SubjectRE: [alsa-devel] [PATCH] ASoC: Add support for multi register mux

> > On 03/26/2014 11:41 PM, Songhee Baek wrote:
> > >> On 03/26/2014 01:02 AM, Arun Shamanna Lakshmi wrote:
> > >>
> > >> The way you describe this it seems to me that a value array for
> > >> this kind of mux would look like.
> > >>
> > >> 0x00000000, 0x00000000, 0x00000001
> > >> 0x00000000, 0x00000000, 0x00000002
> > >> 0x00000000, 0x00000000, 0x00000003
> > >> 0x00000000, 0x00000000, 0x00000004
> > >> 0x00000000, 0x00000000, 0x00000008
> > >> ...
> > >>
> > >> That seems to be extremely tedious. If the MUX uses a one hot
> > >> encoding how about storing the index of the bit in the values array
> > >> and use (1 << value) when writing the value to the register?
> > >
> > > If we store the index of the bit, the value will be duplicated for
> > > each
> > registers inputs since register has 0 to 31bits to shift, then we need
> > to decode the index to interpret value for which registers to set. If
> > we need to interpret the decoded value of index, it is better to have
> > custom put/get function in our driver, isn't it?
> > >
> >
> > I'm not sure I understand. If you use (val / 32) to pick the register
> > and (val %
> > 32) to pick the bit in the register this should work just fine. Maybe
> > I'm missing something. Do you have a real world code example of of the
> > this type of enum is used?
> >
>
> I can use val/32 and val%32 for this multi register mux.

With this logic, put function would be easy however get function becomes tedious due to looping on each bit per register for 3 of them in our case. Rather, it would be easy to identify a unique MUX_OFFSET to distinguish between the 3 registers as shown in the code below.

#define MULTI_MUX_INPUT_OFFSET(n) (5 * n)

int snd_soc_dapm_get_enum_double(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_value *ucontrol)
{
struct snd_soc_codec *codec = snd_soc_dapm_kcontrol_codec(kcontrol);
struct soc_enum *e = (struct soc_enum *)kcontrol->private_value;
unsigned int reg_val, val, reg_idx;

if (e->reg[0] != SND_SOC_NOPM) {
for (reg_idx = 0; reg_idx < e->num_regs; reg_idx) {
reg_val = snd_soc_read(codec, e->reg[reg_idx]);
val = (reg_val >> e->shift_l) & e->mask[reg_idx];
if (val)
val += MULTI_MUX_INPUT_OFFSET(reg_idx);
}
} else {
reg_val = dapm_kcontrol_get_value(kcontrol);
val = (reg_val >> e->shift_l) & e->mask[0];
}

ucontrol->value.enumerated.item[0] = snd_soc_enum_val_to_item(e, val);
if (e->shift_l != e->shift_r) {
val = (reg_val >> e->shift_r) & e->mask[0];
val = snd_soc_enum_val_to_item(e, val);
ucontrol->value.enumerated.item[1] = val;
}

return 0;
}

int snd_soc_dapm_put_enum_double(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_value *ucontrol)
{
struct snd_soc_codec *codec = snd_soc_dapm_kcontrol_codec(kcontrol);
struct snd_soc_card *card = codec->card;
struct soc_enum *e = (struct soc_enum *)kcontrol->private_value;
unsigned int *item = ucontrol->value.enumerated.item;
unsigned int change, i, value, update_idx = 0;
unsigned int mask;
struct snd_soc_dapm_update update;
int ret = 0, reg_val;

if (item[0] >= e->items)
return -EINVAL;

value = snd_soc_enum_item_to_val(e, item[0]) << e->shift_l;
mask = e->mask[0] << e->shift_l;
if (e->shift_l != e->shift_r) {
if (item[1] > e->items)
return -EINVAL;
value |= snd_soc_enum_item_to_val(e, item[1]) << e->shift_l;
mask |= e->mask[0] << e->shift_r;
}

if (e->num_regs < 2) {
goto update_reg;
}

for (i = 0; i < e->num_regs; i++) {
reg_val = value - MULTI_MUX_INPUT_OFFSET(i);

/* checking reg_val is power of 2 : one-hot code */
/* if reg_val after subtract MULTI_MUX_INPUT_OFFSET is not power of 2, reg[i] should be zero */
if (reg_val & (reg_val - 1)) {
/* clear the current input register */
snd_soc_write(codec, e->reg[i], 0);
} else {
/* reg_val is power of 2, store updated info */
value = reg_val;
mask = e->mask[i];
update_idx = i;
}
}

update_reg:
mutex_lock_nested(&card->dapm_mutex, SND_SOC_DAPM_CLASS_RUNTIME);

if (e->reg[update_idx] != SND_SOC_NOPM)
change = snd_soc_test_bits(codec, e->reg[update_idx], mask, value);
else
change = dapm_kcontrol_set_value(kcontrol, value);

if (change) {
if (e->reg[update_idx] != SND_SOC_NOPM) {
update.kcontrol = kcontrol;
update.reg = e->reg[update_idx];
update.mask= mask;
update.val = value;
card->update = &update;
}
ret = soc_dapm_mux_update_power(card, kcontrol, item[0], e);

card->update = NULL;
}
mutex_unlock(&card->dapm_mutex);

if (ret > 0)
soc_dpcm_runtime_update(card);

return change;
}

> > >>> - int reg;
> > >>> + int reg[SOC_ENUM_MAX_REGS];
> > >>> unsigned char shift_l;
> > >>> unsigned char shift_r;
> > >>> unsigned int items;
> > >>> - unsigned int mask;
> > >>> + unsigned int mask[SOC_ENUM_MAX_REGS];
> > >>
> > >> If you make mask and reg pointers instead of arrays this should be
> > >> much more flexible and not be limited to 3 registers.

We will make reg* and mask* instead of arrays and since we use the same structure, the plan is to share the get and put function code.

Thanks.
Songhee.




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