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.
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: ac34df733d2d ("ALSA: usb-audio: scarlett2: Update get_config to do endian conversion") Link: https://github.com/ClangBuiltLinux/linux/issues/1408 Acked-by: Geoffrey D. Bennett g@b4.vu Signed-off-by: Nathan Chancellor nathan@kernel.org ---
v1 -> v2:
* Use temporary variables of proper type rather than casting, as requested by Takashi.
* Mention that there is not a bug at the moment per Geoffrey's comment.
v2 -> v3:
* Restrict scope of buf_16 more, as requested by Geoffrey.
* Add Geoffrey's ack.
v3 -> v4:
* Fix stray newline added below
if (config_item->size >= 8) {
leftover from buf_16's declaration.
sound/usb/mixer_scarlett_gen2.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c index fcba682cd422..161d832cafef 100644 --- a/sound/usb/mixer_scarlett_gen2.c +++ b/sound/usb/mixer_scarlett_gen2.c @@ -1177,6 +1177,7 @@ static int scarlett2_usb_get_config( const struct scarlett2_config *config_item = &scarlett2_config_items[info->has_mixer][config_item_num]; 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; }
base-commit: 0cbbeaf370221fc469c95945dd3c1198865c5fe4