From: Takashi Iwai <tiwai@suse.de>
To: Nathan Chancellor <nathan@kernel.org>
Cc: "Geoffrey D. Bennett" <g@b4.vu>, Jaroslav Kysela <perex@perex.cz>,
Takashi Iwai <tiwai@suse.com>,
Nick Desaulniers <ndesaulniers@google.com>,
alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com
Subject: Re: [PATCH] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config
Date: Fri, 25 Jun 2021 09:45:48 +0200 [thread overview]
Message-ID: <s5heecql74j.wl-tiwai@suse.de> (raw)
In-Reply-To: <20210624212048.1356136-1-nathan@kernel.org>
On Thu, 24 Jun 2021 23:20:48 +0200,
Nathan Chancellor wrote:
>
> 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 post-increment shorthand with the full expression so the
> cast can be added in the right place and the look works as expected.
>
> Fixes: ac34df733d2d ("ALSA: usb-audio: scarlett2: Update get_config to do endian conversion")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1408
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> sound/usb/mixer_scarlett_gen2.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
> index fcba682cd422..c20c7f1ddc50 100644
> --- a/sound/usb/mixer_scarlett_gen2.c
> +++ b/sound/usb/mixer_scarlett_gen2.c
> @@ -1186,7 +1186,7 @@ static int scarlett2_usb_get_config(
> if (err < 0)
> return err;
> if (size == 2)
> - for (i = 0; i < count; i++, (u16 *)buf++)
> + for (i = 0; i < count; i++, buf = (u16 *)buf + 1)
> *(u16 *)buf = le16_to_cpu(*(__le16 *)buf);
That's still too error-prone.
Could you rather introduce another variable of u16 * type, and use it
instead? Ditto for u8 access for the code after that, too.
thanks,
Takashi
next prev parent reply other threads:[~2021-06-25 7:45 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 [this message]
2021-06-25 17:54 ` [PATCH v2] " Nathan Chancellor
2021-06-25 18:43 ` Geoffrey D. Bennett
2021-06-25 20:05 ` [PATCH v3] " Nathan Chancellor
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=s5heecql74j.wl-tiwai@suse.de \
--to=tiwai@suse.de \
--cc=alsa-devel@alsa-project.org \
--cc=clang-built-linux@googlegroups.com \
--cc=g@b4.vu \
--cc=linux-kernel@vger.kernel.org \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=perex@perex.cz \
--cc=tiwai@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).