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SubjectRe: [PATCH] staging: greybus: fix warnings detected by sparse
On Mon, Aug 24, 2020 at 12:41:48PM +0300, Dan Carpenter wrote:
>On Mon, Aug 24, 2020 at 10:50:59AM +0800, Coiby Xu wrote:
>> This patch fix the following warnings from sparse,
>>
>> $ make C=2 drivers/staging/greybus/
>> drivers/staging/greybus/audio_codec.c:691:36: warning: incorrect type in initializer (different base types)
>> drivers/staging/greybus/audio_codec.c:691:36: expected unsigned long long [usertype] formats
>> drivers/staging/greybus/audio_codec.c:691:36: got restricted snd_pcm_format_t [usertype]
>> drivers/staging/greybus/audio_codec.c:701:36: warning: incorrect type in initializer (different base types)
>> drivers/staging/greybus/audio_codec.c:701:36: expected unsigned long long [usertype] formats
>> drivers/staging/greybus/audio_codec.c:701:36: got restricted snd_pcm_format_t [usertype]
>> drivers/staging/greybus/audio_module.c:222:25: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_module.c:222:25: expected restricted __le16 [usertype] data_cport
>> drivers/staging/greybus/audio_module.c:222:25: got unsigned short [usertype] intf_cport_id
>> drivers/staging/greybus/audio_topology.c:460:40: warning: restricted __le32 degrades to integer
>> drivers/staging/greybus/audio_topology.c:691:41: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:691:41: expected unsigned int access
>> drivers/staging/greybus/audio_topology.c:691:41: got restricted __le32 [usertype] access
>> drivers/staging/greybus/audio_topology.c:746:44: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:746:44: expected unsigned int
>> drivers/staging/greybus/audio_topology.c:746:44: got restricted __le32
>> drivers/staging/greybus/audio_topology.c:748:52: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:748:52: expected unsigned int
>> drivers/staging/greybus/audio_topology.c:748:52: got restricted __le32
>> drivers/staging/greybus/audio_topology.c:802:42: warning: restricted __le32 degrades to integer
>> drivers/staging/greybus/audio_topology.c:805:50: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:805:50: expected restricted __le32
>> drivers/staging/greybus/audio_topology.c:805:50: got unsigned int
>> drivers/staging/greybus/audio_topology.c:814:50: warning: restricted __le32 degrades to integer
>> drivers/staging/greybus/audio_topology.c:817:58: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:817:58: expected restricted __le32
>> drivers/staging/greybus/audio_topology.c:817:58: got unsigned int
>> drivers/staging/greybus/audio_topology.c:889:25: warning: incorrect type in assignment (different base types)
>> drivers/staging/greybus/audio_topology.c:889:25: expected unsigned int access
>> drivers/staging/greybus/audio_topology.c:889:25: got restricted __le32 [usertype] access
>>
>> Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
>> ---
>> drivers/staging/greybus/audio_codec.c | 4 ++--
>> drivers/staging/greybus/audio_module.c | 2 +-
>> drivers/staging/greybus/audio_topology.c | 18 +++++++++---------
>> 3 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/staging/greybus/audio_codec.c b/drivers/staging/greybus/audio_codec.c
>> index 74538f8c5fa4..494aa823e998 100644
>> --- a/drivers/staging/greybus/audio_codec.c
>> +++ b/drivers/staging/greybus/audio_codec.c
>> @@ -688,7 +688,7 @@ static struct snd_soc_dai_driver gbaudio_dai[] = {
>> .playback = {
>> .stream_name = "I2S 0 Playback",
>> .rates = SNDRV_PCM_RATE_48000,
>> - .formats = SNDRV_PCM_FORMAT_S16_LE,
>> + .formats = SNDRV_PCM_FMTBIT_S16_LE,
>> .rate_max = 48000,
>> .rate_min = 48000,
>> .channels_min = 1,
>> @@ -698,7 +698,7 @@ static struct snd_soc_dai_driver gbaudio_dai[] = {
>> .capture = {
>> .stream_name = "I2S 0 Capture",
>> .rates = SNDRV_PCM_RATE_48000,
>> - .formats = SNDRV_PCM_FORMAT_S16_LE,
>> + .formats = SNDRV_PCM_FMTBIT_S16_LE,
>> .rate_max = 48000,
>> .rate_min = 48000,
>> .channels_min = 1,
>
>These changes need to be explained better. We're changing formats from
>2 to 1 << 2.
>
>When you're writing commit messages, please imagine me as the target
>audience. I have a fairly decent understanding of the kernel and C, but
>I don't know very much about the sound subsystem.

(Sorry for the late reply! I didn't notice my email client failed to
delivered this email.)

Thank you for showing me SNDRV_PCM_FORMAT_S16_LE != SNDRV_PCM_FMTBIT_S16_LE.
I thought they only differ in type so no domain knowledge is needed.
>
>This code used to work, right? How was it that changing a 2 to a 4
>makes it better? It needs to be explained in the commit message. This
>change probably needs to be split into a separate commit because it
>seems different from the rest of the patch.

After doing some homework on greybus, ALSA, PCM, etc., I think
SNDRV_PCM_FORMAT_S16_LE could be a mistake,

1. According to the struct definition,

struct snd_soc_dai_driver {
...
/* DAI capabilities */
struct snd_soc_pcm_stream capture;
struct snd_soc_pcm_stream playback;
/* SoC PCM stream information */

struct snd_soc_pcm_stream {
const char *stream_name;
u64 formats; /* SNDRV_PCM_FMTBIT_* */
...
};


We should use SNDRV_PCM_FMTBIT_* which is a bit mask while
SNDRV_PCM_FORMAT_* are sequential integers.

2. This "formats" member represent PCM audio's resolution/sample Size,
Byte Order and Sign [1]. In terms of the values,
SNDRV_PCM_FORMAT_S16_LE == SNDRV_PCM_FMTBIT_S8.
Using 8 bits to represent the amplitude of the sound sample may lead to
low quality audio.

3. There is this commit e712bfca1ac1f63f622f87c2f33b57608f2a4d19
("ASoC: codecs: use SNDRV_PCM_FMTBIT_* for format bitmask"),

snd_soc_pcm_stream.formats is a bitmask of SNDRV_PCM_FMTBIT_*,
not of SNDRV_PCM_FORMAT_* (which are sequential integers),
however some of ASoC CODEC drivers use these values instead.

which simply replaced SNDRV_PCM_FORMAT_S16_LE with SNDRV_PCM_FMTBIT_S16_LE.

>
>(Presumably the rest of the patch doesn't affect runtime on little
>endian systems. This is the part which affects runtime so it is
>different from the rest).
>
>> diff --git a/drivers/staging/greybus/audio_module.c b/drivers/staging/greybus/audio_module.c
>> index 16f60256adb2..00848b84b022 100644
>> --- a/drivers/staging/greybus/audio_module.c
>> +++ b/drivers/staging/greybus/audio_module.c
>> @@ -219,7 +219,7 @@ static int gb_audio_add_data_connection(struct gbaudio_module_info *gbmodule,
>>
>> greybus_set_drvdata(bundle, gbmodule);
>> dai->id = 0;
>> - dai->data_cport = connection->intf_cport_id;
>> + dai->data_cport = cpu_to_le16(connection->intf_cport_id);
>> dai->connection = connection;
>> list_add(&dai->list, &gbmodule->data_list);
>>
>
>This is correct, but I think you should change the two places which
>print the data_cport to print the CPU endian value.
>
> 327 list_for_each_entry(dai, &gbmodule->data_list, list) {
> 328 ret = gb_connection_enable(dai->connection);
> 329 if (ret) {
> 330 dev_err(dev,
> 331 "%d:Error while enabling %d:data connection\n",
> 332 ret, dai->data_cport);
> 333 goto disable_data_connection;
> 334 }
> 335 }
>
> 449 list_for_each_entry(dai, &gbmodule->data_list, list) {
> 450 ret = gb_connection_enable(dai->connection);
> 451 if (ret) {
> 452 dev_err(dev,
> 453 "%d:Error while enabling %d:data connection\n",
> 454 ret, dai->data_cport);
> 455 return ret;
> 456 }
> 457 }
>
>Otherwise it's slightly confusing to mix the values.

Thank you for the suggestion! I'll fix it in next version.
>
>The rest of the patch seems fine to me.
>
>regards,
>dan carpenter
>
Thank you for reviewing this patch!

[1] https://wiki.multimedia.cx/index.php/PCM

--
Best regards,
Coiby

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