[alsa-devel] [PATCH v2 14/14] OMAPDSS: HDMI: Implement DSS driver interface for audio

[Tomi Valkeinen]

Hi,

On Thu, 2012-05-03 at 20:44 -0500, Ricardo Neri wrote:
> Implement the DSS device driver audio support interface in the HDMI
> panel driver and generic driver. The implementation relies on the
> IP-specific functions that are defined at DSS probe time.
> 
> At the moment, a hardirq-safe spinlock is used to protect the audio
> functions. This is because such functions might be called while
> holding a lock (this especially true for audio_start/stop). For the
> rest of the audio functions, a mutex could be used in the future as
> the enablement of resources might take too much time.

The series looks good, except locking. Granted, the locking in omapdss
is a bit bad generally also, but here I think it's a bit more broken.

For example, hdmi_panel.c:hdmi_panel_audio_supported() takes the audio
lock, and then uses variables like dssdev->state, and the hdmi video
mode. However, the video functions do not use audio lock, so effectively
the lock doesn't protect at all.

I'm not sure how to fix it, though. I think this shows the shortcomings
of the current locking strategy (or lack of =). What if the audio
functions that can sleep would take the hdmi panel's mutex, and also the
audio spinlock? That would at least fix some of the cases.

 Tomi

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