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Subject[PATCH] ALSA: usb-audio: Fix UAC2 get_ctl request with a RANGE attribute
Date
The layout of the UAC2 Control request and response varies depending on
the request type. With the current implementation, only the Layout 2
Parameter Block (with the 2-byte sized RANGE attribute) is handled
properly. For the Control requests with the 1-byte sized RANGE attribute
(Bass Control, Mid Control, Tremble Control), the response is parsed
incorrectly.

This commit:
* fixes the wLength field value in the request
* fixes parsing the range values from the response

Fixes: 23caaf19b11e ("ALSA: usb-mixer: Add support for Audio Class v2.0")
Signed-off-by: Kirill Marinushkin <k.marinushkin@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Jaejoong Kim <climbbb.kim@gmail.com>
Cc: Bhumika Goyal <bhumirks@gmail.com>
Cc: Stephen Barber <smbarber@chromium.org>
Cc: Julian Scheel <julian@jusst.de>
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.kernel.org
---
sound/usb/mixer.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 2b4ceda36291..20b28a5a1456 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -347,17 +347,20 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,
int validx, int *value_ret)
{
struct snd_usb_audio *chip = cval->head.mixer->chip;
- unsigned char buf[4 + 3 * sizeof(__u32)]; /* enough space for one range */
+ /* enough space for one range */
+ unsigned char buf[sizeof(__u16) + 3 * sizeof(__u32)];
unsigned char *val;
- int idx = 0, ret, size;
+ int idx = 0, ret, val_size, size;
__u8 bRequest;

+ val_size = uac2_ctl_value_size(cval->val_type);
+
if (request == UAC_GET_CUR) {
bRequest = UAC2_CS_CUR;
- size = uac2_ctl_value_size(cval->val_type);
+ size = val_size;
} else {
bRequest = UAC2_CS_RANGE;
- size = sizeof(buf);
+ size = sizeof(__u16) + 3 * val_size;
}

memset(buf, 0, sizeof(buf));
@@ -390,16 +393,17 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,
val = buf + sizeof(__u16);
break;
case UAC_GET_MAX:
- val = buf + sizeof(__u16) * 2;
+ val = buf + sizeof(__u16) + val_size;
break;
case UAC_GET_RES:
- val = buf + sizeof(__u16) * 3;
+ val = buf + sizeof(__u16) + val_size * 2;
break;
default:
return -EINVAL;
}

- *value_ret = convert_signed_value(cval, snd_usb_combine_bytes(val, sizeof(__u16)));
+ *value_ret = convert_signed_value(cval,
+ snd_usb_combine_bytes(val, val_size));

return 0;
}
--
2.13.6
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