[alsa-devel] [PATCH RFC 00/21] ALSA: pcm: add tracepoints for PCM params operation

[Takashi Iwai]

On Sun, 14 May 2017 10:57:35 +0200,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> In the last Audio Mini Conference held with Linux Plumber conference 2016[1], I mentioned about tracepoints for PCM params operation. This patchset is for the idea.
> 
> In ALSA PCM interface, applications can get hardware capability by ioctl(2) with SNDRV_PCM_IOCTL_HW_REFINE/SNDRV_PCM_IOCT_HW_PARAMS in a shape of 'struct snd_pcm_hw_params'. In kernel side, relevant processing is somewhat complicated and developers sometimes have hard time to debug drivers for PCM constraints and rules.
> 
> This patchset adds tracepoints for hw_params operations. When CONFIG_SND_DEBUG is enabled, you can see 'trace_hw_params_mask/trace_hw_params_interval' events of 'snd_pcm' subsystem. When applications execute ioctl(2) with SNDRV_PCM_IOCTL_HW_REFINE/SNDRV_PCM_IOCTL_HW_PARAMS, these events are probed. Developers can get how many PCM rules are added into runtime of PCM substream and which rule changed which parameters.
> 
> This patchset also includes some improvements. The last three commits brings small changes to kernel/userspace interface for error handling.
> 
> I'm happy to receive your comment for this patchset. For your information, low level application of SNDRV_PCM_IOCTL_HW_REFINE operation is available in my github repository[2].

The patches look good through a quick glance.
The only concern I have is the function regression, since there are
lots of code rewrites.  How did you test?


thanks,

Takashi