[alsa-devel] [PATCH - alsa-lib 1/1] Change card/pid get functions to return -ENOSYS if the kernel is too old

[Martin Koegler]

On Fri, Apr 08, 2016 at 11:21:57AM -0400, Adam Goode wrote:
> So there are 2 alternatives I can think of:
> 
> option 1: introduce snd_seq_client_info_get_pid_2() and leave the existing
> function alone. This new function can return a new constant,
> SND_SEQ_CLIENT_INFO_PID_UNKNOWN for missing kernel support. Same for card.
> option 2: introduce snd_seq_client_info_pid_known() that returns a bool if
> there is kernel support. Same for card.

I wouldn't implement option 1. Using that methode for API changes will result in lots of rarely used functions.

Chrome will probable need that information to enable a fallback-code - if a application has no fallback code, 
it has no need for different returncodes. In a few years, most distributions will likely ship kernel including that functions,
so there is no need to for fallback-code and the kernel support check any more.

Why not a snd_seq_client_info_get_capatibilites() returing bit flags: .._CAP_CARD_NUMBER | .._CAP_PID ?

Regards,
Martin