Document the technique for determining if the running kernel supports the new snd_seq_client_info_get_pid and snd_seq_client_info_get_card functions. Also add a little information about how to use these functions and add some cross references.

Signed-off-by: Adam Goode agoode@google.com

diff --git a/src/seq/seq.c b/src/seq/seq.c index 9279830..b206e2f 100644 --- a/src/seq/seq.c +++ b/src/seq/seq.c @@ -1530,7 +1530,25 @@ int snd_seq_client_info_get_error_bounce(const snd_seq_client_info_t *info) * \param info client_info container * \return card number or -1 if value is not available. * - * Only available for SND_SEQ_KERNEL_CLIENT clients. + * Only available for #SND_SEQ_KERNEL_CLIENT clients. + * + * The card number can be used to query state about the hardware + * device providing this client, by concatenating <code>"hw:CARD="</code> + * with the card number and using it as the <code>name</code> parameter + * to #snd_ctl_open(). + * + * \note + * The return value of -1 is returned for two different conditions: when the + * running kernel does not support this operation, and when the client + * does not have a hardware card attached. See + * #snd_seq_client_info_get_pid() for a way to determine if the + * currently running kernel has support for this operation. + * + * \sa snd_seq_client_info_get_pid(), + * snd_card_get_name(), + * snd_card_get_longname(), + * snd_ctl_open(), + * snd_ctl_card_info() */ int snd_seq_client_info_get_card(const snd_seq_client_info_t *info) { @@ -1543,7 +1561,29 @@ int snd_seq_client_info_get_card(const snd_seq_client_info_t *info) * \param info client_info container * \return pid or -1 if value is not available. * - * Only available for SND_SEQ_USER_CLIENT clients. + * Only available for #SND_SEQ_USER_CLIENT clients. + * + * \note + * The functionality for getting a client's PID and getting a + * client's card was added to the kernel at the same time, so you can + * use this function to determine if the running kernel + * supports reporting these values. If your own client has a valid + * PID as reported by this function, then the running kernel supports + * both #snd_seq_client_info_get_card() and #snd_seq_client_info_get_pid(). + * + * \note + * Example code for determining kernel support: + * \code + * int is_get_card_or_pid_supported(snd_seq_t *seq) + * { + * snd_seq_client_info_t *my_client_info; + * snd_seq_client_info_alloca(&my_client_info); + * snd_seq_get_client_info(seq, my_client_info); + * return snd_seq_client_info_get_pid(my_client_info) != -1; + * } + * \endcode + * + * \sa snd_seq_client_info_get_card() */ int snd_seq_client_info_get_pid(const snd_seq_client_info_t *info) {