[alsa-devel] RFC: snd_card_create() function

Takashi Iwai tiwai at suse.de
Thu Jan 15 14:05:08 CET 2009

At Mon, 12 Jan 2009 15:35:19 +0100,
I wrote:
> 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.

Since no big issues came up, I merged that branch to master branch.
Thanks for all your comments.


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