Re: [PATCH 1/2] ALSA: firewire-tascam: Fix infinite loop in snd_tscm_stream_get_rate()

From: Takashi Sakamoto
Date: Mon May 15 2017 - 10:07:42 EST


Hi,

On May 15 2017 17:19, Geert Uytterhoeven wrote:
Obviously the intention was to put a limit on the maximum number of
operations. However, for this to work, the check should be
"&& trials++ < 5", not "|| trials++ < 5".

Fixes: 35efa5c489de63a9 ("ALSA: firewire-tascam: add streaming functionality")
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
Compile-tested only.

Triggered by a false-positive warning from gcc-4.1.2:

warning: âerrâ may be used uninitialized in this function
---
sound/firewire/tascam/tascam-stream.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/firewire/tascam/tascam-stream.c b/sound/firewire/tascam/tascam-stream.c
index f1657a4e0621ef49..e433b92ac6904db5 100644
--- a/sound/firewire/tascam/tascam-stream.c
+++ b/sound/firewire/tascam/tascam-stream.c
@@ -84,7 +84,7 @@ int snd_tscm_stream_get_rate(struct snd_tscm *tscm, unsigned int *rate)
unsigned int trials = 0;
int err;

- while (data == 0x0 || trials++ < 5) {
+ while (data == 0x0 && trials++ < 5) {
err = get_clock(tscm, &data);
if (err < 0)
return err;

Yep. It looks a bug.

...However, removal of the bug causes issue that the driver fails to start a pair of capture/playback PCM substream when application requests them mostly the same time, like jackd process.

I think I did apply the bug as a makeshift workaround, then forgot itself when developing the driver... I'd like to have a bit time for further investigation, then post my fix in this development period.

Please let me keep this patch pending.


Thanks

Takashi Sakamoto