Commit 9a7b7ec3 authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Takashi Iwai
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ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config

Clang warns:

sound/usb/mixer_scarlett_gen2.c:1189:32: warning: expression result
unused [-Wunused-value]
                        for (i = 0; i < count; i++, (u16 *)buf++)
                                                    ^      ~~~~~
1 warning generated.

It appears the intention was to cast the void pointer to a u16 pointer
so that the data could be iterated through like an array of u16 values.
However, the cast happens after the increment because a cast is an
rvalue, whereas the post-increment operator only works on lvalues, so
the loop does not iterate as expected. This is not a bug in practice
because count is not greater than one at the moment but this could
change in the future so this should be fixed.

Replace the cast with a temporary variable of the proper type, which is
less error prone and fixes the iteration. Do the same thing for the
'u8 *' below this if block.

Fixes: ac34df73 ("ALSA: usb-audio: scarlett2: Update get_config to do endian conversion")

Acked-by: default avatarGeoffrey D. Bennett <>
Signed-off-by: default avatarNathan Chancellor <>

Signed-off-by: default avatarTakashi Iwai <>
parent fb3acdb2
......@@ -1177,6 +1177,7 @@ static int scarlett2_usb_get_config(
const struct scarlett2_config *config_item =
int size, err, i;
u8 *buf_8;
u8 value;
/* For byte-sized parameters, retrieve directly into buf */
......@@ -1185,9 +1186,12 @@ static int scarlett2_usb_get_config(
err = scarlett2_usb_get(mixer, config_item->offset, buf, size);
if (err < 0)
return err;
if (size == 2)
for (i = 0; i < count; i++, (u16 *)buf++)
*(u16 *)buf = le16_to_cpu(*(__le16 *)buf);
if (size == 2) {
u16 *buf_16 = buf;
for (i = 0; i < count; i++, buf_16++)
*buf_16 = le16_to_cpu(*(__le16 *)buf_16);
return 0;
......@@ -1197,8 +1201,9 @@ static int scarlett2_usb_get_config(
return err;
/* then unpack from value into buf[] */
buf_8 = buf;
for (i = 0; i < 8 && i < count; i++, value >>= 1)
*(u8 *)buf++ = value & 1;
*buf_8++ = value & 1;
return 0;
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