On Sun, 11 Dec 2016 12:31:38 +0100, Takashi Sakamoto wrote:
In a design of ALSA PCM interface, for PCM frame transmission to/from kernel space, applications can select from two options; direct memory access or ioctl(2). Available options are decided depending on device capacity and machine architecture. Applications can get available options by the first entry of 'struct snd_pcm_hw_params.masks'.
When the mask includes 'SNDRV_PCM_ACCESS_MMAP_xxx', applications can use direct memory access. For this use case, userspace library has two types of PCM API. One is to expose a pointer over the memory to start reading/writing PCM frames. Another is to copy PCM frames between the memory and a given buffer.
Current documentation includes wrong references to these APIs to describe their advantages/disadvantages. This confuses application developers because the references indicate PCM APIs to execute ioctl(2) operation to read/write PCM frames.
This commit fixes the bug.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp
Applied, thanks.
Takashi