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Date: Fri, 14 Oct 2011 13:38:31 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] hda: do not mix output and input
 stream states, RHBZ #740493
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To: =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= <marcandre.lureau@gmail.com>
Cc: alevy@redhat.com, yhalperi@redhat.com, qemu-devel@nongnu.org, =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= <marcandre.lureau@redhat.com>, quintela@redhat.com

   Hi,

>> a) My understanding of this patch is that we move from an array of 16
>> bools representing anything to one array where the 1st 16 represent if
>> there are input and the 2nd 16's reprosenting if there are output for
>> that channel.

Correct.

>> So, what we should do if we migrate from one old version that only has
>> 16 bools?  My understanding is that copying directly is not gonna work?

Yes.  Putting output first increases the chance that it works as sound 
playback is used much more than sound recording.

I think hda-audio doesn't need so safe any running state.  intel-hda 
knows which streams are running and it can call 
intel_hda_notify_codecs() for each stream in intel_hda_post_load().  The 
only problem is that intel_hda_post_load() might get called before 
hda-audio state is loaded.

Now how to handle compatibility?  We can have a running_compat[] array 
with the current (broken) semantics, so we can write out the state which 
older qemu versions expect to see.  Also on load running_compat[] will 
be filled, and any state already set by intel_hda_post_load in 
running_real[] (or however we'll name this) will be kept intact.

cheers,
   Gerd