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| author | Maciej Strozek <mstrozek@opensource.cirrus.com> | 2026-07-20 11:35:05 +0100 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2026-08-05 09:28:59 +0200 |
| commit | 86cac980c9668106b32ffca3bda106cbb6d7ac2b (patch) | |
| tree | dcff04016533bad4a0dea51b5e852c6db4528b2c /include/uapi | |
| parent | eaf46ee96599e20c56c46401c937102f18e081bf (diff) | |
| download | linux-86cac980c9668106b32ffca3bda106cbb6d7ac2b.tar.gz linux-86cac980c9668106b32ffca3bda106cbb6d7ac2b.zip | |
ALSA: control: add ioctl to retrieve full card components
The fixed-size components field in SNDRV_CTL_IOCTL_CARD_INFO can be too
small on systems with many audio devices.
Keep the existing struct snd_ctl_card_info ABI intact and add a new
ioctl SNDRV_CTL_IOCTL_CARD_BYTES that carries a variable-length payload
selected by a type discriminator. The first defined type
SND_CTL_CARD_BTYPE_COMPONENTS returns the full components string. The
ioctl is designed to be reused for other variable-length card payloads
in the future.
The user-space caller may set data_allocated == 0 (or data == NULL) to
query the required length; otherwise the kernel copies the payload into
the user buffer and writes back the actual length in data_len.
When the legacy components field in struct snd_ctl_card_info is
truncated, '>' is written just before the NUL terminator to signal to
user-space that the full string is available via the new ioctl.
card->components is now dynamically allocated and grown in 32 byte
increments via krealloc(), capped at 512 bytes.
Link: https://github.com/alsa-project/alsa-lib/pull/494
Suggested-by: Jaroslav Kysela <perex@perex.cz>
Suggested-by: Takashi Iwai <tiwai@suse.com>
Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260720103505.1860399-2-mstrozek@opensource.cirrus.com
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/sound/asound.h | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h index d3ce75ba938a..500599213f93 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -1058,7 +1058,7 @@ 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 */ @@ -1072,6 +1072,25 @@ 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_BYTES with type SND_CTL_CARD_BTYPE_COMPONENTS + * to retrieve the full string. + */ + +/* Type values for struct snd_ctl_card_bytes::type */ +enum { + SND_CTL_CARD_BTYPE_COMPONENTS = 1, /* full card components string */ +}; + +struct snd_ctl_card_bytes { + __u32 type; /* SND_CTL_CARD_BTYPE_* */ + __u32 data_allocated; /* size of @data buffer in bytes */ + __u32 data_len; /* in/out: actual data length in bytes */ + __u32 reserved; /* explicit pad */ + __u64 data; /* user buffer (pointer stored as __u64) */ +}; + typedef int __bitwise snd_ctl_elem_type_t; #define SNDRV_CTL_ELEM_TYPE_NONE ((__force snd_ctl_elem_type_t) 0) /* invalid */ #define SNDRV_CTL_ELEM_TYPE_BOOLEAN ((__force snd_ctl_elem_type_t) 1) /* boolean type */ @@ -1198,6 +1217,7 @@ 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_BYTES _IOWR('U', 0x02, struct snd_ctl_card_bytes) #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) |