[alsa-devel] [PATCH] plug: Move fast_ops copy after slave configuration.

Reilly Grant reillyeon at qotw.net
Tue Dec 6 03:05:42 CET 2011

The plug plugin copies the fast_ops structure and fast_op_arg from its
slave PCM on initialization and after inserting a new plugin. This works
unless the slave PCM is also an instance of the plug plugin because plug
can change its fast_ops structure during _snd_pcm_hw_params.

Instead of copying fast_ops in snd_pcm_plug_insert_plugins wait until
the end of snd_pcm_plug_hw_params when the slave has been fully

This fixes a crash when two instances of plug are instantiated back to
back and the format conversion plugin inserted by the second is skipped
by the first because the fast_ops pointer is not properly updated.
 src/pcm/pcm_plug.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/pcm/pcm_plug.c b/src/pcm/pcm_plug.c
index e9d2923..72456d5 100644
--- a/src/pcm/pcm_plug.c
+++ b/src/pcm/pcm_plug.c
@@ -659,8 +659,6 @@ static int snd_pcm_plug_insert_plugins(snd_pcm_t *pcm,
 		if (err) {
 			plug->gen.slave = new;
-			pcm->fast_ops = new->fast_ops;
-			pcm->fast_op_arg = new->fast_op_arg;
@@ -1049,6 +1047,9 @@ static int snd_pcm_plug_hw_params(snd_pcm_t *pcm,
snd_pcm_hw_params_t *params)
 	snd_pcm_unlink_hw_ptr(pcm, plug->req_slave);
 	snd_pcm_unlink_appl_ptr(pcm, plug->req_slave);
+	pcm->fast_ops = slave->fast_ops;
+	pcm->fast_op_arg = slave->fast_op_arg;
 	snd_pcm_link_hw_ptr(pcm, slave);
 	snd_pcm_link_appl_ptr(pcm, slave);
 	return 0;

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