[alsa-devel] [PATCH v3 0/2] ALSA: Add PCM USER_PVERSION ioctl

[Takashi Sakamoto]

Hi,

On Jun 27 2017 19:29, Takashi Iwai wrote:
> Hi,
> 
> this is a revised patchset that is applied on top of the current
> for-next branch, in order to optimize the appl_ptr sync on x86-64,
> adapting the alsa-lib side change by Sakamoto-san's patchset.
> 
> Basically it adds a new ioctl for receiving the supported PCM protocol
> version from user-space side, and change the mmap code to allow only
> disabling the PCM status record depending on the supported protocol
> version.  The former patch is identical with the previous version,
> only the latter one differs.
> 
> The corresponding alsa-lib patch will follow.
> 
> 
> thanks,
> 
> Takashi
> 
> ===
> 
> Takashi Iwai (2):
>    ALSA: pcm: Add an ioctl to specify the supported protocol version
>    ALSA: pcm: Disable only control mmap for explicit appl_ptr sync
> 
>   include/sound/pcm.h         |  1 +
>   include/uapi/sound/asound.h |  3 ++-
>   sound/core/pcm_compat.c     |  1 +
>   sound/core/pcm_native.c     | 29 ++++++++++++++++++++++++-----
>   4 files changed, 28 insertions(+), 6 deletions(-)

Reviewed-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>

I note that the idea of USER_PVERSION ioctl is itself worth for the 
other interfaces/protocols such as control. In the interfaces/protocols, 
many structures have reserved members. As Iwai-san described in the 
first patch, when changing them to utilize these reserved members, this 
idea is a solution to balance compatibility and extensibility.


Thanks

Takashi Sakamoto