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 <[email protected]>
---
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);
return 0;
}
base-commit: 5c89c2c7fbfa9124dd521c375b9c82b9ed75bc28
--
2.32.0.93.g670b81a890
On Thu, Jun 24, 2021 at 02:20:48PM -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.
>
> 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.
look -> loop
> 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 <[email protected]>
> ---
> 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);
> return 0;
> }
Thanks Nathan!
FYI: although incorrect, this caused no bug as there is not yet any
case where count > 1.
Acked-by: Geoffrey D. Bennett <[email protected]>
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 <[email protected]>
> ---
> 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
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 <[email protected]>
---
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;
+
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;
+ 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
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 <[email protected]>
> ---
>
> 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;
Regardless:
Acked-by: Geoffrey D. Bennett <[email protected]>
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
>
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 <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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
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 <[email protected]>
> > ---
> >
> > 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 <[email protected]>
>
> 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
> >
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 <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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
--
2.32.0.93.g670b81a890
On Fri, Jun 25, 2021 at 01:11:51PM -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.
Your note about no bug which was added in v2 went missing in v3:
> > 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 <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
>
> 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
> --
> 2.32.0.93.g670b81a890
>
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 <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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
On Sun, 27 Jun 2021 07:12:03 +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. 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 <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
>
> 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.
Thanks, applied now.
Takashi