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 v5] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Sat, 26 Jun 2021 22:12:03 -0700 [thread overview] Message-ID: <20210627051202.1888250-1-nathan@kernel.org> (raw) In-Reply-To: <20210625202604.GB23780@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. 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 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. v4 -> v5 (or how many times does it take Nathan to get a patch right): * Re-add note about no bug that was dropped in v3 by accident, as noticed by Geoffrey. My apologies for the multiple revisions. 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 -- 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>, Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com> Cc: Nathan Chancellor <nathan@kernel.org>, clang-built-linux@googlegroups.com, alsa-devel@alsa-project.org, Nick Desaulniers <ndesaulniers@google.com>, linux-kernel@vger.kernel.org Subject: [PATCH v5] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Sat, 26 Jun 2021 22:12:03 -0700 [thread overview] Message-ID: <20210627051202.1888250-1-nathan@kernel.org> (raw) In-Reply-To: <20210625202604.GB23780@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. 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 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. v4 -> v5 (or how many times does it take Nathan to get a patch right): * Re-add note about no bug that was dropped in v3 by accident, as noticed by Geoffrey. My apologies for the multiple revisions. 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 -- 2.32.0.93.g670b81a890
next prev parent reply other threads:[~2021-06-27 5:18 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 ` Nathan Chancellor [this message] 2021-06-27 5:12 ` [PATCH v5] " Nathan Chancellor 2021-07-01 17:12 ` Takashi Iwai 2021-07-01 17:12 ` Takashi Iwai 2021-06-25 20:08 ` [PATCH v2] " Nathan Chancellor 2021-06-25 20:08 ` Nathan Chancellor
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