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seq: improve documentation about new get pid/card functions

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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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Adam Goode 2017-01-03 08:33:42 -05:00 • committed by Takashi Iwai
parent 6f7eaf92e7
commit 1eddf1f918
1 changed files with 42 additions and 2 deletions
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44
src/seq/seq.c
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@ -1530,7 +1530,25 @@ int snd_seq_client_info_get_error_bounce(const snd_seq_client_info_t *info)
* \param info client_info container * \param info client_info container
* \return card number or -1 if value is not available. * \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) 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 * \param info client_info container
* \return pid or -1 if value is not available. * \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) int snd_seq_client_info_get_pid(const snd_seq_client_info_t *info)
{ {