Re: [PATCH] ALSA: pcm: Introduce protocol version field to sw_params

From: Takashi Iwai <tiwai@suse.de>
To: Jaroslav Kysela <perex@perex.cz>
Cc: alsa-devel@alsa-project.org
Subject: Re: [PATCH] ALSA: pcm: Introduce protocol version field to sw_params
Date: Mon, 21 Jul 2014 09:02:57 +0200	[thread overview]
Message-ID: <s5hfvhvi47y.wl%tiwai@suse.de> (raw)
In-Reply-To: <53C82872.3040101@perex.cz>

At Thu, 17 Jul 2014 21:48:02 +0200,
Jaroslav Kysela wrote:
> 
> Date 16.7.2014 17:54, Takashi Iwai wrote:
> > For controlling the new fields more strictly, add sw_params.proto
> > field indicating the protocol version of the user-space.  User-space
> > should fill the SNDRV_PCM_VERSION value it's built with, then kernel
> > can know whether the new fields should be evaluated or not.
> > 
> > And now tstamp_type field is evaluated only when the valid value is
> > set there.  This avoids the wrong override of tstamp_type to zero,
> > which is SNDRV_PCM_TSTAMP_TYPE_GETTIMEOFDAY.
> > 
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> >  include/uapi/sound/asound.h | 4 ++--
> >  sound/core/pcm_native.c     | 6 ++++--
> >  2 files changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
> > index a7e062f91f39..c9fd199b9330 100644
> > --- a/include/uapi/sound/asound.h
> > +++ b/include/uapi/sound/asound.h
> > @@ -391,8 +391,8 @@ struct snd_pcm_sw_params {
> >  	snd_pcm_uframes_t silence_threshold;	/* min distance from noise for silence filling */
> >  	snd_pcm_uframes_t silence_size;		/* silence block size */
> >  	snd_pcm_uframes_t boundary;		/* pointers wrap point */
> > -	unsigned int tstamp_type;		/* timestamp type */
> > -	int pads;				/* alignment, reserved */
> > +	unsigned int tstamp_type;		/* timestamp type (req. proto >= 2.0.12) */
> > +	unsigned int proto;			/* protocol version */
> 
> I would switch the positions of tstamp_type and proto... It seems
> logical that all new member added after proto are dependent on this value.

Yeah, right.  I kept the order just because I thought of users of
already published tree including tstamp_type.  But, considering it
again, since the branch is obviously for development-only, I guess
this won't be too bad to swap the fields.  (And thanks to the proto
number check, the old branch wouldn't be broken too much.)

I'll swap the fields in the next revision.

thanks,

Takashi