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control: ucm: add ioctl to retrieve full card components

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The fixed-size components field in SNDRV_CTL_IOCTL_CARD_INFO can be too
small on systems with many audio devices. The kernel [1] will provide a
new ioctl to read the full string while truncating the original in
card_info if it grows too big. Make sure alsa-lib can read the full
string if the original is truncated.

[1] https://lore.kernel.org/all/20260303145815.9930-1-mstrozek@opensource.cirrus.com/

Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>
This commit is contained in:
Maciej Strozek 2026-02-19 13:46:20 +00:00
parent 75ed5f05ba
commit 22c3701630
4 changed files with 61 additions and 6 deletions
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15
include/local.h
View file

@ -101,7 +101,6 @@
#define _snd_pcm_sw_params snd_pcm_sw_params
#define _snd_pcm_status snd_pcm_status
#define _snd_ctl_card_info snd_ctl_card_info
#define _snd_ctl_elem_id snd_ctl_elem_id
#define _snd_ctl_elem_list snd_ctl_elem_list
#define _snd_ctl_elem_info snd_ctl_elem_info
@ -226,6 +225,20 @@
#include "seq_midi_event.h"
#include "list.h"
/* V2 structure - increased components string from 128 bytes to 512 bytes */
struct _snd_ctl_card_info {
int card; /* card number */
int pad; /* reserved for future (was type) */
unsigned char id[16]; /* ID of card (user selectable) */
unsigned char driver[16]; /* Driver name */
unsigned char name[32]; /* Short name of soundcard */
unsigned char longname[80]; /* name + info text about soundcard */
unsigned char reserved_[16]; /* reserved for future (was ID of mixer) */
unsigned char mixername[80]; /* visual mixer identification */
char components[512];
};
struct _snd_async_handler {
enum {
SND_ASYNC_HANDLER_GENERIC,

14
include/sound/uapi/asound.h
View file

@ -1044,7 +1044,7 @@ struct snd_timer_tread {
* *
****************************************************************************/
#define SNDRV_CTL_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 9)
#define SNDRV_CTL_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 10)
struct snd_ctl_card_info {
int card; /* card number */
@ -1058,6 +1058,17 @@ struct snd_ctl_card_info {
unsigned char components[128]; /* card components / fine identification, delimited with one space (AC97 etc..) */
};
/*
* Card components can exceed the fixed 128 bytes in snd_ctl_card_info.
* Use SNDRV_CTL_IOCTL_CARD_COMPONENTS to retrieve the full string.
*
*/
struct snd_ctl_card_components {
int card; /* card number */
unsigned int length; /* returned length of components string for ioctl query */
unsigned char *components; /* user buffer for components string */
};
typedef int __bitwise snd_ctl_elem_type_t;
#define SNDRV_CTL_ELEM_TYPE_NONE ((snd_ctl_elem_type_t) 0) /* invalid */
#define SNDRV_CTL_ELEM_TYPE_BOOLEAN ((snd_ctl_elem_type_t) 1) /* boolean type */
@ -1184,6 +1195,7 @@ struct snd_ctl_tlv {
#define SNDRV_CTL_IOCTL_PVERSION _IOR('U', 0x00, int)
#define SNDRV_CTL_IOCTL_CARD_INFO _IOR('U', 0x01, struct snd_ctl_card_info)
#define SNDRV_CTL_IOCTL_CARD_COMPONENTS _IOWR('U', 0x02, struct snd_ctl_card_components)
#define SNDRV_CTL_IOCTL_ELEM_LIST _IOWR('U', 0x10, struct snd_ctl_elem_list)
#define SNDRV_CTL_IOCTL_ELEM_INFO _IOWR('U', 0x11, struct snd_ctl_elem_info)
#define SNDRV_CTL_IOCTL_ELEM_READ _IOWR('U', 0x12, struct snd_ctl_elem_value)