Re: [alsa-devel] commit bd5389278c96f585afcac4058420e4f3ac201d2a introduce big problem

8 Nov 2011

      At Tue, 8 Nov 2011 17:16:33 +0800,
Scott Jiang wrote:
...
Hi Takash,
commit bd5389278c96f585afcac4058420e4f3ac201d2a
Author: Takashi Iwai tiwai@suse.de
Date:   Fri Aug 21 01:18:00 2009 +0200
pcm: workaround for avoiding automatic start in mmap mode

In the normal mmap mode, the stream isn't started automatically even after
the data >= start_threshold has been written.   However, in the
mmap-emulation mode, the stream is started because it uses
snd_pcm_write_areas() internally.

As a workaround for this inconsistency, start_threshold value is changed
dynamically in sw_parmams and mmap_commit callbacks in mmap-emul plugin.
Meanwhile, start_threshold for slave PCM is set to boundary so that only
this plugin (or the one over it) can control the start of the stream.

This will fix problems in some apps using pulse plugin in the mmap mode.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

src/pcm/pcm_mmap_emul.c
This commit caused codec using mmap-emul plugin can't work.
My config file list below:
bfin-ad1836.pcm.default {
        @args [ CARD ]
        @args.CARD {
                type string
        }
        type plug
        slave.pcm {
                type mmap_emul
                slave.pcm {
                        type hw
                        card $CARD
                        format S32_LE
                        rate 48000
                }
        }
}
Alsa will not send SNDRV_PCM_IOCTL_START to driver.
And how are you testing it?  The whole background is missing...
Takashi