[alsa-devel] [PATCH 1/5] allow up to 32 PCM devices

[Takashi Iwai]

At Thu, 13 May 2010 10:21:26 +0800,
Wu Fengguang wrote:
> 
> On Wed, May 12, 2010 at 06:55:09PM +0800, Takashi Iwai wrote:
> > At Wed, 12 May 2010 12:20:33 +0200,
> > Clemens Ladisch wrote:
> > > 
> > > Takashi Iwai wrote:
> > > > Wu Fengguang wrote:
> > > > > > Jaroslav Kysela wrote:
> > > > > > > I don't agree to have only 4 slots for soundcards in the static minor 
> > > > > > > numbering. Maybe the driver should be converted to use subdevices or we 
> > > > > > > might drop the static minor number allocation at all (it might have only 
> > > > > > > impact for old distros).
> > > > > 
> > > > > Jaroslav, will there be so many sound cards in one system?
> > > > 
> > > > In the old time, yes.  Now we have less and less PCI slots.
> > > > In theory, we may have lots of USB audio devices, though :)
> > > 
> > > I implemented CONFIG_SND_DYNAMIC_MINORS because people had been asking
> > > for more than eight cards.  (And by now I have lots of cards too,
> > > although my computer probably isn't very typical.)
> > > 
> > > Anyway, static numbering is needed only for systems without udev/devfs,
> > > and there we shouldn't change it for backwards compatibility.  The HDA
> > > driver already requires kernels >= 2.6, so I don't see a problem with
> > > requiring CONFIG_SND_DYNAMIC_MINORS to get all HDMI outputs.
> > 
> > Right.  We can make it dependent.
> > 
> 
> Like this?
> 
>  config SND_HDA_CODEC_INTELHDMI
>  	bool "Build INTEL HDMI HD-audio codec support"
> +	select SND_DYNAMIC_MINORS
>  	default y
> 
> That will effectively turn on CONFIG_SND_DYNAMIC_MINORS by default
> (distribution kernels will have to enable it).

It's always a question whether we use "depends on" or "select".
The former is safer while the latter is more intuitive.

In this particular case, I think "select" would be OK.
If other guys have no objection, please repost the patch so that I can
pick it up later.

> Another backwards compatible solution is to fall back to the two
> reserved values. This makes me a bit more comfortable :)

As mentioned in another post, I don't see a big merit by it.
In short: don't touch a working code :)  The non-dynamic minors are
only for old stuff, better to keep as is.


thanks,

Takashi

> --- drm-intel.orig/include/sound/minors.h	2010-05-13 10:06:52.000000000 +0800
> +++ drm-intel/include/sound/minors.h	2010-05-13 10:10:06.000000000 +0800
> @@ -35,7 +35,9 @@
>  #define SNDRV_MINOR_TIMER		(SNDRV_MINOR_GLOBAL + 1 * 32)
>  
>  #ifndef CONFIG_SND_DYNAMIC_MINORS
> -						/* 2 - 3 (reserved) */
> +
> +#define SNDRV_MINOR_BACKUP1		2
> +#define SNDRV_MINOR_BACKUP2		3
>  #define SNDRV_MINOR_HWDEP		4	/* 4 - 7 */
>  #define SNDRV_MINOR_RAWMIDI		8	/* 8 - 15 */
>  #define SNDRV_MINOR_PCM_PLAYBACK	16	/* 16 - 23 */
> --- drm-intel.orig/sound/core/sound.c	2010-05-13 10:06:04.000000000 +0800
> +++ drm-intel/sound/core/sound.c	2010-05-13 10:11:19.000000000 +0800
> @@ -269,8 +269,14 @@ int snd_register_device_for_dev(int type
>  	minor = snd_find_free_minor();
>  #else
>  	minor = snd_kernel_minor(type, card, dev);
> -	if (minor >= 0 && snd_minors[minor])
> -		minor = -EBUSY;
> +	if (minor >= 0) {
> +		if (snd_minors[minor])
> +			minor = SNDRV_MINOR_BACKUP1;
> +		if (snd_minors[minor])
> +			minor = SNDRV_MINOR_BACKUP2;
> +		if (snd_minors[minor])
> +			minor = -EBUSY;
> +	}
>  #endif
>  	if (minor < 0) {
>  		mutex_unlock(&sound_mutex);
> 
> Thanks,
> Fengguang
>