[alsa-devel] [RFC] ASoC: pcm: Trigger all commands on error

[Markus Pargmann]

On Tue, Oct 08, 2013 at 11:44:57AM +0100, Mark Brown wrote:
> On Tue, Oct 08, 2013 at 11:48:39AM +0200, Markus Pargmann wrote:
> > On Tue, Oct 08, 2013 at 10:34:13AM +0100, Mark Brown wrote:
> 
> > > I meant just unwinding the things done in the trigger call.
> 
> > You mean unwinding when we detect the error? If we return the
> > error code from the trigger function, the pcm_native.c will still
> > trigger a STOP command which is executed on all components.
> 
> Sure, but it's another way of getting consistency and does seem a bit
> more obvious.

It is still not consistent as we get an additional STOP after cleanly
unwinding the START:

snd_pcm_do_start()
    soc_pcm_trigger() # START
        codec_dai->driver->ops->trigger() # START
	platform->driver->ops->trigger() # Assuming an error here

	unwind:
        codec_dai->driver->ops->trigger() # STOP

A failed snd_pcm_do_start() is detected, so undo_start is called:

snd_pcm_undo_start()
    soc_pcm_trigger() # STOP
        codec_dai->driver->ops->trigger() # STOP
	platform->driver->ops->trigger() # STOP
	cpu_dai->driver->ops->trigger() # STOP

Now all component trigger functions are called without a matching START
command.

> 
> > > > Another possibility is to explicitly allow multiple _STOPs. Then I could
> > > > fix the driver to store the clock state. But I would prefer a generic
> > > > solution.
> 
> > > You're going to have to handle this anyway to be robust - what happens
> > > if it's the clock enable that fails?
> 
> > If clk_enable fails, we can return an error code in the mxs-saif trigger
> > function. Of course the error handling is missing here, but it is not
> > necessary to store the state of the clock to handle errors properly.
> 
> Right, but then _STOP will be called without the clock having been
> successfully enabled so you'll have an unbalanced clk_disable().

_STOP is only called as long as the error handling is not working
properly. Otherwise STOP should not be called for a failed START.

Regards,

Markus

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