Re: [alsa-devel] [PATCH v3 3/3] ASoC: cros_ec_codec: Add codec driver for Cros EC

[Cheng-yi Chiang]

On Thu, Jan 17, 2019 at 12:25 PM Cheng-yi Chiang <cychiang@xxxxxxxxxxxx> wrote:
>
> Hi Guenter,
>
> Thanks for the review!
>
> On Wed, Jan 16, 2019 at 2:18 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >
> > On Wed, Dec 26, 2018 at 03:03:19PM +0800, Cheng-Yi Chiang wrote:
> > > Add a codec driver to control ChromeOS EC codec.
> > >
> > > Use EC Host command to enable/disable I2S recording and control other
> > > configurations.
> > >
> > > Signed-off-by: Cheng-Yi Chiang <cychiang@xxxxxxxxxxxx>
> > > ---
> > > Changes in v3:
> > > 1.remove cros_ec_codec.h.
> > > 2.Fix error code overriding in
> > >     set_i2s_config
> > >     set_i2s_sample_depth
> > >     set_bclk
> > >     get_ec_mic_gain
> > >     set_ec_mic_gain
> > >     enable_i2s
> > > 3.Fix missing return code in cros_ec_i2s_set_dai_fmt.
> > > 4.Simplify return code in cros_ec_i2s_hw_params and mic_gain_put.
> > > 5.Remove useless debug message in cros_ec_codec_platform_probe.
> > >
> > >  MAINTAINERS                      |   2 +
> > >  sound/soc/codecs/Kconfig         |   8 +
> > >  sound/soc/codecs/Makefile        |   2 +
> > >  sound/soc/codecs/cros_ec_codec.c | 454 +++++++++++++++++++++++++++++++
> > >  4 files changed, 466 insertions(+)
> > >  create mode 100644 sound/soc/codecs/cros_ec_codec.c
> > >
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index 05e1922624e58..d66f80f3252d7 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -3638,8 +3638,10 @@ F:     drivers/platform/chrome/
> > >
> > >  CHROMEOS EC CODEC DRIVER
> > >  M:   Cheng-Yi Chiang <cychiang@xxxxxxxxxxxx>
> > > +R:   Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> > >  S:   Maintained
> > >  F:   Documentation/devicetree/bindings/sound/google,cros-ec-codec.txt
> > > +F:   sound/soc/codecs/cros_ec_codec.*
> > >
> > >  CIRRUS LOGIC AUDIO CODEC DRIVERS
> > >  M:   Brian Austin <brian.austin@xxxxxxxxxx>
> > > diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
> > > index 87cb9c51e6f5a..0b36428159b71 100644
> > > --- a/sound/soc/codecs/Kconfig
> > > +++ b/sound/soc/codecs/Kconfig
> > > @@ -50,6 +50,7 @@ config SND_SOC_ALL_CODECS
> > >       select SND_SOC_BT_SCO
> > >       select SND_SOC_BD28623
> > >       select SND_SOC_CQ0093VC
> > > +     select SND_SOC_CROS_EC_CODEC
> >
> > This unconditionally selects SND_SOC_CROS_EC_CODEC, but SND_SOC_CROS_EC_CODEC
> > depends on MFD_CROS_EC. This is missing an "if MFD_CROS_EC" qualifier.
> >
> Will fix in v4.
> > >       select SND_SOC_CS35L32 if I2C
> > >       select SND_SOC_CS35L33 if I2C
> > >       select SND_SOC_CS35L34 if I2C
> > > @@ -457,6 +458,13 @@ config SND_SOC_CPCAP
> > >  config SND_SOC_CQ0093VC
> > >       tristate
> > >
> > > +config SND_SOC_CROS_EC_CODEC
> > > +     tristate "codec driver for ChromeOS EC"
> > > +     depends on MFD_CROS_EC
> > > +     help
> > > +       If you say yes here you will get support for the
> > > +       ChromeOS Embedded Controller's Audio Codec.
> > > +
> > >  config SND_SOC_CS35L32
> > >       tristate "Cirrus Logic CS35L32 CODEC"
> > >       depends on I2C
> > > diff --git a/sound/soc/codecs/Makefile b/sound/soc/codecs/Makefile
> > > index 9bb3346fab2fe..3cfd8f5f61705 100644
> > > --- a/sound/soc/codecs/Makefile
> > > +++ b/sound/soc/codecs/Makefile
> > > @@ -42,6 +42,7 @@ snd-soc-bd28623-objs := bd28623.o
> > >  snd-soc-bt-sco-objs := bt-sco.o
> > >  snd-soc-cpcap-objs := cpcap.o
> > >  snd-soc-cq93vc-objs := cq93vc.o
> > > +snd-soc-cros-ec-codec-objs := cros_ec_codec.o
> > >  snd-soc-cs35l32-objs := cs35l32.o
> > >  snd-soc-cs35l33-objs := cs35l33.o
> > >  snd-soc-cs35l34-objs := cs35l34.o
> > > @@ -310,6 +311,7 @@ obj-$(CONFIG_SND_SOC_BD28623)     += snd-soc-bd28623.o
> > >  obj-$(CONFIG_SND_SOC_BT_SCO) += snd-soc-bt-sco.o
> > >  obj-$(CONFIG_SND_SOC_CQ0093VC) += snd-soc-cq93vc.o
> > >  obj-$(CONFIG_SND_SOC_CPCAP)  += snd-soc-cpcap.o
> > > +obj-$(CONFIG_SND_SOC_CROS_EC_CODEC)  += snd-soc-cros-ec-codec.o
> > >  obj-$(CONFIG_SND_SOC_CS35L32)        += snd-soc-cs35l32.o
> > >  obj-$(CONFIG_SND_SOC_CS35L33)        += snd-soc-cs35l33.o
> > >  obj-$(CONFIG_SND_SOC_CS35L34)        += snd-soc-cs35l34.o
> > > diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
> > > new file mode 100644
> > > index 0000000000000..85ea23f4b681c
> > > --- /dev/null
> > > +++ b/sound/soc/codecs/cros_ec_codec.c
> > > @@ -0,0 +1,454 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Driver for ChromeOS Embedded Controller codec.
> > > + *
> > > + * This driver uses the cros-ec interface to communicate with the ChromeOS
> > > + * EC for audio function.
> > > + */
> > > +
> > > +#include <linux/delay.h>
> > > +#include <linux/device.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/mfd/cros_ec.h>
> > > +#include <linux/mfd/cros_ec_commands.h>
> > > +#include <linux/module.h>
> > > +#include <linux/platform_device.h>
> > > +#include <sound/pcm.h>
> > > +#include <sound/pcm_params.h>
> > > +#include <sound/soc.h>
> > > +#include <sound/tlv.h>
> > > +
> > > +#define MAX_GAIN 43
> >
> > Is there some reason for this magic number ? What does it reflect ?
> >
>
> This value is determined by the EC chip to represent the maximum gain
> in dB that EC codec can support.
> Since it might be different in the future for different EC chip, it
> needs to be adjustable.
> I plan to pass this value as "max-dmic-gain" from device property.
> This driver can lookup the property it its probe function, and modify
> the max value in mixer control for gain accordingly.
> I could not find similar use case in other codec driver but it should be doable.
> Please let me know if this is not encouraged.
>
> > > +
> > > +#define DRV_NAME "cros-ec-codec"
> > > +
> > > +/**
> > > + * struct cros_ec_codec_data - ChromeOS EC codec driver data.
> > > + * @dev:         Device structure used in sysfs.
> > > + * @ec_device:   cros_ec_device structure to talk to the physical device.
> > > + * @component:   Pointer to the component.
> > > + */
> > > +struct cros_ec_codec_data {
> > > +     struct device *dev;
> > > +     struct cros_ec_device *ec_device;
> > > +     struct snd_soc_component *component;
> > > +};
> > > +
> > > +static const DECLARE_TLV_DB_SCALE(ec_mic_gain_tlv, 0, 100, 0);
> > > +/*
> > > + * Wrapper for EC command.
> > > + */
> > > +static int ec_command(struct snd_soc_component *component, int version,
> > > +                   int command, u8 *outdata, int outsize,
> > > +                   u8 *indata, int insize)
> > > +{
> > > +     struct cros_ec_codec_data *codec_data =
> > > +             snd_soc_component_get_drvdata(component);
> > > +     struct cros_ec_device *ec_device = codec_data->ec_device;
> > > +     struct cros_ec_command *msg;
> > > +     int ret;
> > > +
> > > +     msg = kzalloc(sizeof(*msg) + max(insize, outsize), GFP_KERNEL);
> > > +     if (!msg)
> > > +             return -ENOMEM;
> >
> > As far as I can see, the calling parameter is always "struct ec_param_codec_i2s".
> > With that in mind, this code seems unnecessarily complex. Is this code expected
> > to be called multiple times in parallel and requires multiple instances of
> > struct ec_param_codec_i2s to be allocated ? Even if so, why not just use
> > a local variable / array ?
> >
> > [ This makes me wonder how EC transfers are synchronized in
> >   cros_ec_cmd_xfer_status() and below. Does anyone know ? I don't immedately
> >   see it.
> > ]
>
> I agree with you suggestion of using local variable.
> All the needed commands are subcommands in EC_CMD_CODEC_I2S command.
> So "struct ec_param_codec_i2s" is the only param that will be passed
> to ec_command function.
> This ec_command function can be greatly simplified.
>
> As for multiple access to this ec_command function, I need to dig more into it.
> There are locks in stream and kcontrol to guard the access
> respectively, but I am not sure if stream and kcontrol will access
> this ec_command function at the same time.
> It should be safer to use local variable to hold this parameter.
>

Unfortunately I found that for ec command that needs a response (e.g.
getting mic gain from EC),
I still need to allocate buffer for message based on max(insize,outsize).

But for all other cases where there is no need for response, the code
can be simplified.

So I plan is to rename this function to ec_command_with_resp

static int ec_command_with_resp(struct snd_soc_component *component,
                                u8 *outdata, int outsize,
                                u8 *indata, int insize)

And add another function for commands that do not need response:

static int ec_command_no_resp(struct snd_soc_component *component,
                              struct ec_param_codec_i2s* param)

Many places that use ec_command_no_resp can be greatly simplified like

static int set_i2s_bclk(struct snd_soc_component *component, uint32_t bclk)
{
        struct ec_param_codec_i2s param;

        param.cmd = EC_CODEC_I2S_SET_BCLK;
        param.bclk = bclk;

        return ec_command_no_resp(component, &param);
}



> >
> > > +
> > > +     msg->version = version;
> > > +     msg->command = command;
> > > +     msg->outsize = outsize;
> > > +     msg->insize = insize;
> > > +
> > > +     if (outsize)
> > > +             memcpy(msg->data, outdata, outsize);
> > > +
> > > +     ret = cros_ec_cmd_xfer_status(ec_device, msg);
> > > +     if (ret > 0 && insize)
> > > +             memcpy(indata, msg->data, insize);
> > > +
> > > +     kfree(msg);
> > > +     return ret;
> >
> > I know this is wide-spread in cros_ec drivers, but that doesn't make it better.
> > The positive return value isn't used anywhere. On top of that, the called low
> > level code already generates error messages. As a result, the code calling this
> > function is unnecessarily complex. If the function was to return 0 for success
> > and a negative error code otherwise, pret much all all callers could be
> > simplified to
> >
> >         return ec_command(...);
> >
>
> My intention was to print some error message so I can identify the
> command that failed.
> cros_ec_cmd_xfer and cros_ec_cmd_xfer_status have messages for error,
> but not the command it tried to send.
> I can remove them since they cause unnecessary complexity.
> I guess I can still rely on error messages in upper layers to tell
> what command fails.
> Will follow your advice in v4.
>
> Thanks again!
>
>
>
> > > +}
> > > +
> > > +static int set_i2s_config(struct snd_soc_component *component,
> > > +                       enum ec_i2s_config i2s_config)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     int ret;
> > > +
> > > +     dev_dbg(component->dev, "%s set I2S format to %u\n", __func__,
> > > +             i2s_config);
> > > +
> > > +     param.cmd = EC_CODEC_I2S_SET_CONFIG;
> > > +     param.i2s_config = i2s_config;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      NULL, 0);
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev,
> > > +                     "set I2S format to %u command returned %d\n",
> > > +                     i2s_config, ret);
> > > +             return ret;
> > > +     }
> > > +     return 0;
> > > +}
> > > +
> > > +static int cros_ec_i2s_set_dai_fmt(struct snd_soc_dai *dai, unsigned int fmt)
> > > +{
> > > +     struct snd_soc_component *component = dai->component;
> > > +     enum ec_i2s_config i2s_config;
> > > +
> > > +     switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
> > > +     case SND_SOC_DAIFMT_CBS_CFS:
> > > +             break;
> > > +     default:
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     switch (fmt & SND_SOC_DAIFMT_INV_MASK) {
> > > +     case SND_SOC_DAIFMT_NB_NF:
> > > +             break;
> > > +     default:
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     switch (fmt & SND_SOC_DAIFMT_FORMAT_MASK) {
> > > +     case SND_SOC_DAIFMT_I2S:
> > > +             i2s_config = EC_DAI_FMT_I2S;
> > > +             break;
> > > +
> > > +     case SND_SOC_DAIFMT_RIGHT_J:
> > > +             i2s_config = EC_DAI_FMT_RIGHT_J;
> > > +             break;
> > > +
> > > +     case SND_SOC_DAIFMT_LEFT_J:
> > > +             i2s_config = EC_DAI_FMT_LEFT_J;
> > > +             break;
> > > +
> > > +     case SND_SOC_DAIFMT_DSP_A:
> > > +             i2s_config = EC_DAI_FMT_PCM_A;
> > > +             break;
> > > +
> > > +     case SND_SOC_DAIFMT_DSP_B:
> > > +             i2s_config = EC_DAI_FMT_PCM_B;
> > > +             break;
> > > +
> > > +     default:
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     return set_i2s_config(component, i2s_config);
> > > +}
> > > +
> > > +static int set_i2s_sample_depth(struct snd_soc_component *component,
> > > +                             enum ec_sample_depth_value depth)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     int ret;
> > > +
> > > +     dev_dbg(component->dev, "%s set depth to %u\n", __func__, depth);
> > > +
> > > +     param.cmd = EC_CODEC_SET_SAMPLE_DEPTH;
> > > +     param.depth = depth;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      NULL, 0);
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev, "I2S sample depth %u returned %d\n",
> > > +                     depth, ret);
> > > +             return ret;
> > > +     }
> > > +     return 0;
> > > +}
> > > +
> > > +static int set_bclk(struct snd_soc_component *component, uint32_t bclk)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     int ret;
> > > +
> > > +     dev_dbg(component->dev, "%s set i2s bclk to %u\n", __func__, bclk);
> > > +
> > > +     param.cmd = EC_CODEC_I2S_SET_BCLK;
> > > +     param.bclk = bclk;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      NULL, 0);
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev, "I2S set bclk %u command returned %d\n",
> > > +                     bclk, ret);
> > > +             return ret;
> > > +     }
> > > +     return 0;
> > > +}
> > > +
> > > +static int cros_ec_i2s_hw_params(struct snd_pcm_substream *substream,
> > > +                              struct snd_pcm_hw_params *params,
> > > +                              struct snd_soc_dai *dai)
> > > +{
> > > +     struct snd_soc_component *component = dai->component;
> > > +     int frame_size;
> > > +     unsigned int rate, bclk;
> > > +     int ret;
> > > +
> > > +     frame_size = snd_soc_params_to_frame_size(params);
> > > +     if (frame_size < 0) {
> > > +             dev_err(component->dev, "Unsupported frame size: %d\n",
> > > +                     frame_size);
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     rate = params_rate(params);
> > > +     if (rate != 48000) {
> > > +             dev_err(component->dev, "Unsupported rate\n");
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     switch (params_format(params)) {
> > > +     case SNDRV_PCM_FORMAT_S16_LE:
> > > +             ret = set_i2s_sample_depth(component, EC_CODEC_SAMPLE_DEPTH_16);
> > > +             break;
> > > +     case SNDRV_PCM_FORMAT_S24_LE:
> > > +             ret = set_i2s_sample_depth(component, EC_CODEC_SAMPLE_DEPTH_24);
> > > +             break;
> > > +     default:
> > > +             return -EINVAL;
> >
> > There is quite some inconsistency in error messages. Is there some kind of
> > plan behind it ? Do the error mesages above add value, but an error message
> > here wouldn't ?
> >
> > > +     }
> > > +     if (ret < 0)
> > > +             return ret;
> > > +
> > > +     bclk = snd_soc_params_to_bclk(params);
> > > +     return set_bclk(component, bclk);
> > > +}
> > > +
> > > +static const struct snd_soc_dai_ops cros_ec_i2s_dai_ops = {
> > > +     .hw_params = cros_ec_i2s_hw_params,
> > > +     .set_fmt = cros_ec_i2s_set_dai_fmt,
> > > +};
> > > +
> > > +struct snd_soc_dai_driver cros_ec_dai[] = {
> > > +     {
> > > +             .name = "cros_ec_codec I2S",
> > > +             .id = 0,
> > > +             .capture = {
> > > +                     .stream_name = "I2S Capture",
> > > +                     .channels_min = 2,
> > > +                     .channels_max = 2,
> > > +                     .rates = SNDRV_PCM_RATE_48000,
> > > +                     .formats = SNDRV_PCM_FMTBIT_S16_LE |
> > > +                                SNDRV_PCM_FMTBIT_S24_LE,
> > > +             },
> > > +             .ops = &cros_ec_i2s_dai_ops,
> > > +     }
> > > +};
> > > +
> > > +static int get_ec_mic_gain(struct snd_soc_component *component,
> > > +                        u8 *left, u8 *right)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     struct ec_response_codec_gain resp;
> > > +     int ret;
> > > +
> > > +     param.cmd = EC_CODEC_GET_GAIN;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      (u8 *)&resp, sizeof(resp));
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev, "I2S get gain command returned %d\n",
> > > +                     ret);
> > > +             return ret;
> > > +     }
> > > +
> > > +     *left = resp.left;
> > > +     *right = resp.right;
> > > +
> > > +     dev_dbg(component->dev, "%s get mic gain %u, %u\n", __func__,
> > > +             *left, *right);
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static int mic_gain_get(struct snd_kcontrol *kcontrol,
> > > +                     struct snd_ctl_elem_value *ucontrol)
> > > +{
> > > +     struct snd_soc_component *component =
> > > +             snd_soc_kcontrol_component(kcontrol);
> > > +     u8 left, right;
> > > +     int ret;
> > > +
> > > +     ret = get_ec_mic_gain(component, &left, &right);
> > > +     if (ret)
> > > +             return ret;
> > > +
> > > +     ucontrol->value.integer.value[0] = left;
> > > +     ucontrol->value.integer.value[1] = right;
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static int set_ec_mic_gain(struct snd_soc_component *component,
> > > +                        u8 left, u8 right)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     int ret;
> > > +
> > > +     dev_dbg(component->dev, "%s set mic gain to %u, %u\n",
> > > +             __func__, left, right);
> > > +
> > > +     param.cmd = EC_CODEC_SET_GAIN;
> > > +     param.gain.left = left;
> > > +     param.gain.right = right;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      NULL, 0);
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev, "I2S set gain command returned %d\n",
> > > +                     ret);
> > > +             return ret;
> > > +     }
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static int mic_gain_put(struct snd_kcontrol *kcontrol,
> > > +                     struct snd_ctl_elem_value *ucontrol)
> > > +{
> > > +     struct snd_soc_component *component =
> > > +             snd_soc_kcontrol_component(kcontrol);
> > > +     int left = ucontrol->value.integer.value[0];
> > > +     int right = ucontrol->value.integer.value[1];
> > > +
> > > +     if (left > MAX_GAIN || right > MAX_GAIN)
> > > +             return -EINVAL;
> > > +
> > > +     return set_ec_mic_gain(component, (u8)left, (u8)right);
> > > +}
> > > +
> > > +static const struct snd_kcontrol_new cros_ec_snd_controls[] = {
> > > +     SOC_DOUBLE_EXT_TLV("EC Mic Gain", SND_SOC_NOPM, SND_SOC_NOPM, 0, 43, 0,
> > > +                        mic_gain_get, mic_gain_put, ec_mic_gain_tlv)
> > > +};
> > > +
> > > +static int enable_i2s(struct snd_soc_component *component, int enable)
> > > +{
> > > +     struct ec_param_codec_i2s param;
> > > +     int ret;
> > > +
> > > +     dev_dbg(component->dev, "%s set i2s to %u\n", __func__, enable);
> > > +
> > > +     param.cmd = EC_CODEC_I2S_ENABLE;
> > > +     param.i2s_enable = enable;
> > > +
> > > +     ret = ec_command(component, 0, EC_CMD_CODEC_I2S,
> > > +                      (u8 *)&param, sizeof(param),
> > > +                      NULL, 0);
> > > +     if (ret < 0) {
> > > +             dev_err(component->dev, "I2S enable %d command returned %d\n",
> > > +                     enable, ret);
> > > +             return ret;
> > > +     }
> > > +     return 0;
> > > +}
> > > +
> > > +static int cros_ec_i2s_enable_event(struct snd_soc_dapm_widget *w,
> > > +                                 struct snd_kcontrol *kcontrol, int event)
> > > +{
> > > +     struct snd_soc_component *component =
> > > +             snd_soc_dapm_to_component(w->dapm);
> > > +
> > > +     switch (event) {
> > > +     case SND_SOC_DAPM_PRE_PMU:
> > > +             dev_dbg(component->dev,
> > > +                     "%s got SND_SOC_DAPM_PRE_PMU event\n", __func__);
> > > +             return enable_i2s(component, 1);
> > > +
> > > +     case SND_SOC_DAPM_PRE_PMD:
> > > +             dev_dbg(component->dev,
> > > +                     "%s got SND_SOC_DAPM_PRE_PMD event\n", __func__);
> > > +             return enable_i2s(component, 0);
> > > +     }
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +/*
> > > + * The goal of this DAPM route is to turn on/off I2S using EC
> > > + * host command when capture stream is started/stopped.
> > > + */
> > > +static const struct snd_soc_dapm_widget cros_ec_dapm_widgets[] = {
> > > +     SND_SOC_DAPM_INPUT("DMIC"),
> > > +
> > > +     /*
> > > +      * Control EC to enable/disable I2S.
> > > +      */
> > > +     SND_SOC_DAPM_SUPPLY("I2S Enable", SND_SOC_NOPM,
> > > +                         0, 0, cros_ec_i2s_enable_event,
> > > +                         SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_PRE_PMD),
> > > +
> > > +     SND_SOC_DAPM_AIF_OUT("I2STX", "I2S Capture", 0, SND_SOC_NOPM, 0, 0),
> > > +};
> > > +
> > > +static const struct snd_soc_dapm_route cros_ec_dapm_routes[] = {
> > > +     { "I2STX", NULL, "DMIC" },
> > > +     { "I2STX", NULL, "I2S Enable" },
> > > +};
> > > +
> > > +static const struct snd_soc_component_driver cros_ec_component_driver = {
> > > +     .controls               = cros_ec_snd_controls,
> > > +     .num_controls           = ARRAY_SIZE(cros_ec_snd_controls),
> > > +     .dapm_widgets           = cros_ec_dapm_widgets,
> > > +     .num_dapm_widgets       = ARRAY_SIZE(cros_ec_dapm_widgets),
> > > +     .dapm_routes            = cros_ec_dapm_routes,
> > > +     .num_dapm_routes        = ARRAY_SIZE(cros_ec_dapm_routes),
> > > +};
> > > +
> > > +/*
> > > + * Platform device and platform driver fro cros-ec-codec.
> > > + */
> > > +static int cros_ec_codec_platform_probe(struct platform_device *pd)
> > > +{
> > > +     struct device *dev = &pd->dev;
> > > +     struct cros_ec_device *ec_device = dev_get_drvdata(pd->dev.parent);
> > > +     struct cros_ec_codec_data *codec_data;
> > > +     int rc;
> > > +
> > > +     codec_data = devm_kzalloc(dev, sizeof(struct cros_ec_codec_data),
> > > +                               GFP_KERNEL);
> > > +     if (!codec_data)
> > > +             return -ENOMEM;
> > > +
> > > +     codec_data->dev = dev;
> > > +     codec_data->ec_device = ec_device;
> > > +
> > > +     platform_set_drvdata(pd, codec_data);
> > > +
> > > +     rc = snd_soc_register_component(dev, &cros_ec_component_driver,
> > > +                                     cros_ec_dai, ARRAY_SIZE(cros_ec_dai));
> > > +
> > > +     return 0;
> >
> > Why ignore errors from snd_soc_register_component() ? Is this on purpose
> > or an oversight ?
> >
> > > +}
> > > +
> > > +#ifdef CONFIG_OF
> > > +static const struct of_device_id cros_ec_codec_of_match[] = {
> > > +     { .compatible = "google,cros-ec-codec" },
> > > +     {},
> > > +};
> > > +MODULE_DEVICE_TABLE(of, cros_ec_codec_of_match);
> > > +#endif
> > > +
> > > +static struct platform_driver cros_ec_codec_platform_driver = {
> > > +     .driver = {
> > > +             .name = DRV_NAME,
> > > +             .of_match_table = of_match_ptr(cros_ec_codec_of_match),
> > > +     },
> > > +     .probe = cros_ec_codec_platform_probe,
> > > +};
> > > +
> > > +module_platform_driver(cros_ec_codec_platform_driver);
> >
> > The "platform" in the various variable and function names don't really
> > add any value.
> >
> > > +
> > > +MODULE_LICENSE("GPL v2");
> > > +MODULE_DESCRIPTION("ChromeOS EC codec driver");
> > > +MODULE_AUTHOR("Cheng-Yi Chiang <cychiang@xxxxxxxxxxxx>");
> > > +MODULE_ALIAS("platform:" DRV_NAME);