SAMA5D2 specific, I should add.
> On 27 Aug 2023, at 23:23, Tim Hardisty <t...@hardisty.co.uk> wrote:
>
> The classD driver DOES register itself as /dev/audio/pcm0, and works
> correctly as such with nx_player.
>
> The conversions are wav (or mp3 etc) to pcm.
>
> Don’t if we’re talking cross purposes or the classd driver works in a way it
> shouldn’t!!!
>
>> On 27 Aug 2023, at 23:00, Gregory Nutt <spudan...@gmail.com> wrote:
>>
>> Also, I don't think the /dev/audio/pcm0 device you are talking about is
>> what you think it is. It is a character driver but not the Class D lower
>> half. So, yes it can be opened.
>>
>> /Caveat: It has been ages since I worked with the audio subsystem so I
>> might be completely wrong./
>>
>> /dev/audio/pcm0 is the audio subsystem interface device. The "pcm"
>> indicates that it used the PCM software decoder (that will convert PCM file
>> data to WAV). It gets set up like:
>>
>> boards/arm/sama5/sama5d4-ek/src/sam_wm8904.c:
>>
>> pcm = pcm_decode_initialize(wm8904);
>> snprintf(devname, 12, "pcm%d", minor);
>> ret = audio_register(devname, pcm);
>>
>> And a character driver is registered by the audio subsystem in audio/audio.c:
>>
>> int audio_register(FAR const char *name, FAR struct
>> audio_lowerhalf_s *dev)
>> {
>> ...
>>
>> audinfo("Registering %s\n", path);
>> return register_driver(path, &g_audioops, 0666, upper);
>> }
>>
>> Where g_audioops is the character driver operations structure:
>>
>> static const struct file_operations g_audioops =
>> {
>> audio_open, /* open */
>> audio_close, /* close */
>> audio_read, /* read */
>> audio_write, /* write */
>> NULL, /* seek */
>> audio_ioctl, /* ioctl */
>> };
>>
>> So the registered pcm0 is the standard audio buffer chain configured for PCM
>> file to WAV conversion and terminating with a wm8904 DAC.
>>
>> I don't believe that there is any way to get the Class D audio_ops_s as a
>> driver under /dev. Nothing like that is supported.
>>
