At Mon, 12 Jan 2009 17:08:28 +0100, Krzysztof Helt wrote: > > On Mon, 12 Jan 2009 15:35:19 +0100 > Takashi Iwai <tiwai@xxxxxxx> 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. > > Another approach is PTR_ERR macro used already in the kernel > (see include/linux/err.h). > It encodes the error code in the returned pointer value. There > are already hndy macros/inlines to get this code, test error, etc. Yep. However, as I mentioned in the paragraph after the text above, it gives you little advantage in this case. If an error occurs, the new function returns a non-NULL value. Since the old caller side does only a NULL-check, it would accept the error pointer as is, ended up an Oops. More badly, this old-style return-value check can't be detected at the compile time because the API (at least the function calling) is unchanged. So, PTR_ERR() is nice to be introduced at the first place but pretty bad as a transition from a NULL/non-NULL API. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
