[alsa-devel] RFC: snd_card_create() function

[Takashi Iwai]

At Mon, 12 Jan 2009 14:42:06 +0000,
James Courtier-Dutton wrote:
> 
> Sounds good to me.
> One can keep the wrapper outside of the kernel, and only available in
> alsa-driver for those out of tree people.

Yes, that's good.
I think it'd be better to do that after one kernel-cycle later for a
softer landing, though.


thanks,

Takashi


> Kind Regards
> 
> James
> 
> 
> 
> 
> 2009/1/12 Takashi Iwai <tiwai at suse.de>:
> > Hi,
> >
> > so far, we use snd_card_new() function to create a card instance.
> > A known problem regarding this API is that it doesn't return a proper
> > error code, thus the probe callback always returns -ENOMEM (or
> > whatever the driver defines) no matter which error occurred actually.
> > A typical case is the card slot conflict.  Even in such a case, it
> > returns -ENOMEM, which may mislead the user.
> >
> > For fixing this situation, I'd like to convert from snd_card_new() to
> > a new function, snd_card_create():
> >
> > int snd_card_create(int idx, const char *id,
> >                    struct module *module, int extra_size,
> >                    struct snd_card **card_ret);
> >
> > and provides snd_card_new() as a wrapper with deprecated flag:
> >
> > static inline __deprecated
> > struct snd_card *snd_card_new(int idx, const char *id,
> >                              struct module *module, int extra_size)
> > {
> >        struct snd_card *card;
> >        if (snd_card_create(idx, id, module, extra_size, &card) < 0)
> >                return NULL;
> >        return card;
> > }
> >
> > The merit of creating a new function is that the older and out-of-tree
> > codes (like xfi) work without modification.  There is alternative
> > option, namely to use PTR_ERR() and keep the function as is.
> > But this has no advantage in practice -- it can't detect the old API
> > at build time, and it may Oops.
> >
> > The preliminary patches are found in test/snd_card_new-err branch
> > of sound git tree:
> >  git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6.git test/snd_card_new-err
> >
> > If anyone finds problems with this, please let me know.
> >
> >
> > thanks,
> >
> > Takashi
> > _______________________________________________
> > Alsa-devel mailing list
> > Alsa-devel at alsa-project.org
> > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
> >
>