From: Nathan Chancellor <nathan@kernel.org>
To: "Geoffrey D. Bennett" <g@b4.vu>, Jaroslav Kysela <perex@perex.cz>,
Takashi Iwai <tiwai@suse.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH v3] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config
Date: Fri, 25 Jun 2021 13:05:50 -0700 [thread overview]
Message-ID: <20210625200549.1061113-1-nathan@kernel.org> (raw)
In-Reply-To: <20210625184342.GA23780@m.b4.vu>
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.
sound/usb/mixer_scarlett_gen2.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
index fcba682cd422..07ba0ef884a2 100644
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -1177,17 +1177,22 @@ 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 */
if (config_item->size >= 8) {
+
size = config_item->size / 8 * count;
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 +1202,9 @@ 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
--
2.32.0.93.g670b81a890
next prev parent reply other threads:[~2021-06-25 20:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-24 21:20 [PATCH] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Nathan Chancellor
2021-06-25 2:07 ` Geoffrey D. Bennett
2021-06-25 7:45 ` Takashi Iwai
2021-06-25 17:54 ` [PATCH v2] " Nathan Chancellor
2021-06-25 18:43 ` Geoffrey D. Bennett
2021-06-25 20:05 ` Nathan Chancellor [this message]
2021-06-25 20:11 ` [PATCH v4] " Nathan Chancellor
2021-06-25 20:26 ` Geoffrey D. Bennett
2021-06-27 5:12 ` [PATCH v5] " Nathan Chancellor
2021-07-01 17:12 ` Takashi Iwai
2021-06-25 20:08 ` [PATCH v2] " Nathan Chancellor
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