[ALSA] Add TLV support to snd-usb-audio driver
Added TLV-read support to snd-usb-audio driver for passing
the volume dB scale information to user-space.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/usb/usbmixer.c b/sound/usb/usbmixer.c
index 491e975..e516d6a 100644
--- a/sound/usb/usbmixer.c
+++ b/sound/usb/usbmixer.c
@@ -37,6 +37,7 @@
#include <sound/control.h>
#include <sound/hwdep.h>
#include <sound/info.h>
+#include <sound/tlv.h>
#include "usbaudio.h"
@@ -416,6 +417,26 @@
return set_ctl_value(cval, SET_CUR, (cval->control << 8) | channel, value);
}
+/*
+ * TLV callback for mixer volume controls
+ */
+static int mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
+ unsigned int size, unsigned int __user *_tlv)
+{
+ struct usb_mixer_elem_info *cval = kcontrol->private_data;
+ DECLARE_TLV_DB_SCALE(scale, 0, 0, 0);
+
+ if (size < sizeof(scale))
+ return -ENOMEM;
+ /* USB descriptions contain the dB scale in 1/256 dB unit
+ * while ALSA TLV contains in 1/100 dB unit
+ */
+ scale[2] = (convert_signed_value(cval, cval->min) * 100) / 256;
+ scale[3] = (convert_signed_value(cval, cval->res) * 100) / 256;
+ if (copy_to_user(_tlv, scale, sizeof(scale)))
+ return -EFAULT;
+ return 0;
+}
/*
* parser routines begin here...
@@ -933,6 +954,12 @@
}
strlcat(kctl->id.name + len, control == USB_FEATURE_MUTE ? " Switch" : " Volume",
sizeof(kctl->id.name));
+ if (control == USB_FEATURE_VOLUME) {
+ kctl->tlv.c = mixer_vol_tlv;
+ kctl->vd[0].access |=
+ SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+ SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
+ }
break;
default: