[ALSA] Control API - TLV implementation for additional information like dB scale

This patch implements a TLV mechanism to transfer an additional information
like dB scale to the user space. The types might be extended in future.
Acked-by: Takashi Iwai <tiwai@suse.de>

Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/sound/asound.h b/include/sound/asound.h
index 41885f48ad91..76a20406bd18 100644
--- a/include/sound/asound.h
+++ b/include/sound/asound.h
@@ -688,7 +688,7 @@ struct snd_timer_tread {
  *                                                                          *
  ****************************************************************************/
 
-#define SNDRV_CTL_VERSION               SNDRV_PROTOCOL_VERSION(2, 0, 3)
+#define SNDRV_CTL_VERSION               SNDRV_PROTOCOL_VERSION(2, 0, 4)
 
 struct snd_ctl_card_info {
         int card;                       /* card number */
@@ -818,6 +818,12 @@ struct snd_ctl_elem_value {
         unsigned char reserved[128-sizeof(struct timespec)];
 };
 
+struct snd_ctl_tlv {
+        unsigned int numid;     /* control element numeric identification */
+        unsigned int length;    /* in bytes aligned to 4 */
+        unsigned int tlv[0];    /* first TLV */
+};
+
 enum {
         SNDRV_CTL_IOCTL_PVERSION = _IOR('U', 0x00, int),
         SNDRV_CTL_IOCTL_CARD_INFO = _IOR('U', 0x01, struct snd_ctl_card_info),
@@ -831,6 +837,7 @@ enum {
         SNDRV_CTL_IOCTL_ELEM_ADD = _IOWR('U', 0x17, struct snd_ctl_elem_info),
         SNDRV_CTL_IOCTL_ELEM_REPLACE = _IOWR('U', 0x18, struct snd_ctl_elem_info),
         SNDRV_CTL_IOCTL_ELEM_REMOVE = _IOWR('U', 0x19, struct snd_ctl_elem_id),
+        SNDRV_CTL_IOCTL_TLV_READ = _IOWR('U', 0x1a, struct snd_ctl_tlv),
         SNDRV_CTL_IOCTL_HWDEP_NEXT_DEVICE = _IOWR('U', 0x20, int),
         SNDRV_CTL_IOCTL_HWDEP_INFO = _IOR('U', 0x21, struct snd_hwdep_info),
         SNDRV_CTL_IOCTL_PCM_NEXT_DEVICE = _IOR('U', 0x30, int),