From: Nathan Chancellor <nathan@kernel.org> To: "Geoffrey D. Bennett" <g@b4.vu> Cc: alsa-devel@alsa-project.org, Nick Desaulniers <ndesaulniers@google.com>, linux-kernel@vger.kernel.org, Takashi Iwai <tiwai@suse.com>, clang-built-linux@googlegroups.com Subject: Re: [PATCH v2] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Fri, 25 Jun 2021 13:08:00 -0700 [thread overview] Message-ID: <YNY3oF3RkbZRk2Ri@Ryzen-9-3900X.localdomain> (raw) In-Reply-To: <20210625184342.GA23780@m.b4.vu> On Sat, Jun 26, 2021 at 04:13:42AM +0930, Geoffrey D. Bennett wrote: > On Fri, Jun 25, 2021 at 10:54:19AM -0700, 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. 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: 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> > > --- > > > > v1 -> v2: > > > > * Use temporary variables of proper type rather than casting, as > > requested by Takashi. I did not include Geoffrey's ack for this > > reason. > > > > * Mention that there is not a bug at the moment per Geoffrey's comment. > > > > 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..b13903bed330 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) { > > + u16 *buf_16; > > + > > I would prefer that the u16 *buf_16 declaration above be removed from > there... > > > 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) { > > + buf_16 = buf; > > ...and combined with the assignment here, like: u16 *buf_16 = buf; Thanks for pointing it out, I was not paying enough attention to realize that the scope could be reduced. v3 sent with your Ack added, thank you for taking a look in a quick manner! Cheers, Nathan > Regardless: > > Acked-by: Geoffrey D. Bennett <g@b4.vu> > > And, thanks again! > > > + 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 > >
WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <nathan@kernel.org> To: "Geoffrey D. Bennett" <g@b4.vu> Cc: clang-built-linux@googlegroups.com, alsa-devel@alsa-project.org, Nick Desaulniers <ndesaulniers@google.com>, linux-kernel@vger.kernel.org, Takashi Iwai <tiwai@suse.com> Subject: Re: [PATCH v2] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Fri, 25 Jun 2021 13:08:00 -0700 [thread overview] Message-ID: <YNY3oF3RkbZRk2Ri@Ryzen-9-3900X.localdomain> (raw) In-Reply-To: <20210625184342.GA23780@m.b4.vu> On Sat, Jun 26, 2021 at 04:13:42AM +0930, Geoffrey D. Bennett wrote: > On Fri, Jun 25, 2021 at 10:54:19AM -0700, 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. 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: 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> > > --- > > > > v1 -> v2: > > > > * Use temporary variables of proper type rather than casting, as > > requested by Takashi. I did not include Geoffrey's ack for this > > reason. > > > > * Mention that there is not a bug at the moment per Geoffrey's comment. > > > > 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..b13903bed330 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) { > > + u16 *buf_16; > > + > > I would prefer that the u16 *buf_16 declaration above be removed from > there... > > > 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) { > > + buf_16 = buf; > > ...and combined with the assignment here, like: u16 *buf_16 = buf; Thanks for pointing it out, I was not paying enough attention to realize that the scope could be reduced. v3 sent with your Ack added, thank you for taking a look in a quick manner! Cheers, Nathan > Regardless: > > Acked-by: Geoffrey D. Bennett <g@b4.vu> > > And, thanks again! > > > + 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 20:08 UTC|newest] Thread overview: 22+ 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 2021-06-24 21:20 ` Nathan Chancellor 2021-06-25 2:07 ` Geoffrey D. Bennett 2021-06-25 2:07 ` Geoffrey D. Bennett 2021-06-25 7:45 ` Takashi Iwai 2021-06-25 7:45 ` Takashi Iwai 2021-06-25 17:54 ` [PATCH v2] " Nathan Chancellor 2021-06-25 17:54 ` Nathan Chancellor 2021-06-25 18:43 ` Geoffrey D. Bennett 2021-06-25 18:43 ` Geoffrey D. Bennett 2021-06-25 20:05 ` [PATCH v3] " Nathan Chancellor 2021-06-25 20:05 ` Nathan Chancellor 2021-06-25 20:11 ` [PATCH v4] " Nathan Chancellor 2021-06-25 20:11 ` Nathan Chancellor 2021-06-25 20:26 ` Geoffrey D. Bennett 2021-06-25 20:26 ` Geoffrey D. Bennett 2021-06-27 5:12 ` [PATCH v5] " Nathan Chancellor 2021-06-27 5:12 ` Nathan Chancellor 2021-07-01 17:12 ` Takashi Iwai 2021-07-01 17:12 ` Takashi Iwai 2021-06-25 20:08 ` Nathan Chancellor [this message] 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=YNY3oF3RkbZRk2Ri@Ryzen-9-3900X.localdomain \ --to=nathan@kernel.org \ --cc=alsa-devel@alsa-project.org \ --cc=clang-built-linux@googlegroups.com \ --cc=g@b4.vu \ --cc=linux-kernel@vger.kernel.org \ --cc=ndesaulniers@google.com \ --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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.