diff mbox series

Input: touchscreen - Avoid bitwise vs logical OR warning

Message ID 20211014205757.3474635-1-nathan@kernel.org (mailing list archive)
State Accepted
Commit a02dcde595f7cbd240ccd64de96034ad91cffc40
Headers show
Series Input: touchscreen - Avoid bitwise vs logical OR warning | expand

Commit Message

Nathan Chancellor Oct. 14, 2021, 8:57 p.m. UTC 
A new warning in clang points out a few places in this driver where a
bitwise OR is being used with boolean types:

drivers/input/touchscreen.c:81:17: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
        data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This use of a bitwise OR is intentional, as bitwise operations do not
short circuit, which allows all the calls to touchscreen_get_prop_u32()
to happen so that the last parameter is initialized while coalescing the
results of the calls to make a decision after they are all evaluated.

To make this clearer to the compiler, use the '|=' operator to assign
the result of each touchscreen_get_prop_u32() call to data_present,
which keeps the meaning of the code the same but makes it obvious that
every one of these calls is expected to happen.

Link: https://github.com/ClangBuiltLinux/linux/issues/1472
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/input/touchscreen.c | 42 ++++++++++++++++++-------------------
 1 file changed, 21 insertions(+), 21 deletions(-)


base-commit: a41392e0877a271007e9209e63c34cab7527eb43

Comments

Nick Desaulniers Oct. 14, 2021, 9:02 p.m. UTC | #1 
On Thu, Oct 14, 2021 at 1:58 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> A new warning in clang points out a few places in this driver where a
> bitwise OR is being used with boolean types:
>
> drivers/input/touchscreen.c:81:17: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
>         data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
>                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This use of a bitwise OR is intentional, as bitwise operations do not
> short circuit, which allows all the calls to touchscreen_get_prop_u32()
> to happen so that the last parameter is initialized while coalescing the
> results of the calls to make a decision after they are all evaluated.
>
> To make this clearer to the compiler, use the '|=' operator to assign
> the result of each touchscreen_get_prop_u32() call to data_present,
> which keeps the meaning of the code the same but makes it obvious that
> every one of these calls is expected to happen.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1472
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks for the patch!
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  drivers/input/touchscreen.c | 42 ++++++++++++++++++-------------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/input/touchscreen.c b/drivers/input/touchscreen.c
> index dd18cb917c4d..4620e20d0190 100644
> --- a/drivers/input/touchscreen.c
> +++ b/drivers/input/touchscreen.c
> @@ -80,27 +80,27 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
>
>         data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
>                                                 input_abs_get_min(input, axis_x),
> -                                               &minimum) |
> -                      touchscreen_get_prop_u32(dev, "touchscreen-size-x",
> -                                               input_abs_get_max(input,
> -                                                                 axis_x) + 1,
> -                                               &maximum) |
> -                      touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
> -                                               input_abs_get_fuzz(input, axis_x),
> -                                               &fuzz);
> +                                               &minimum);
> +       data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-x",
> +                                                input_abs_get_max(input,
> +                                                                  axis_x) + 1,
> +                                                &maximum);
> +       data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
> +                                                input_abs_get_fuzz(input, axis_x),
> +                                                &fuzz);
>         if (data_present)
>                 touchscreen_set_params(input, axis_x, minimum, maximum - 1, fuzz);
>
>         data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-y",
>                                                 input_abs_get_min(input, axis_y),
> -                                               &minimum) |
> -                      touchscreen_get_prop_u32(dev, "touchscreen-size-y",
> -                                               input_abs_get_max(input,
> -                                                                 axis_y) + 1,
> -                                               &maximum) |
> -                      touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
> -                                               input_abs_get_fuzz(input, axis_y),
> -                                               &fuzz);
> +                                               &minimum);
> +       data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-y",
> +                                                input_abs_get_max(input,
> +                                                                  axis_y) + 1,
> +                                                &maximum);
> +       data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
> +                                                input_abs_get_fuzz(input, axis_y),
> +                                                &fuzz);
>         if (data_present)
>                 touchscreen_set_params(input, axis_y, minimum, maximum - 1, fuzz);
>
> @@ -108,11 +108,11 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
>         data_present = touchscreen_get_prop_u32(dev,
>                                                 "touchscreen-max-pressure",
>                                                 input_abs_get_max(input, axis),
> -                                               &maximum) |
> -                      touchscreen_get_prop_u32(dev,
> -                                               "touchscreen-fuzz-pressure",
> -                                               input_abs_get_fuzz(input, axis),
> -                                               &fuzz);
> +                                               &maximum);
> +       data_present |= touchscreen_get_prop_u32(dev,
> +                                                "touchscreen-fuzz-pressure",
> +                                                input_abs_get_fuzz(input, axis),
> +                                                &fuzz);
>         if (data_present)
>                 touchscreen_set_params(input, axis, 0, maximum, fuzz);
>
>
> base-commit: a41392e0877a271007e9209e63c34cab7527eb43
> --
> 2.33.1.637.gf443b226ca
>
>
diff mbox series

Patch

diff --git a/drivers/input/touchscreen.c b/drivers/input/touchscreen.c
index dd18cb917c4d..4620e20d0190 100644
--- a/drivers/input/touchscreen.c
+++ b/drivers/input/touchscreen.c
@@ -80,27 +80,27 @@  void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 
 	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
 						input_abs_get_min(input, axis_x),
-						&minimum) |
-		       touchscreen_get_prop_u32(dev, "touchscreen-size-x",
-						input_abs_get_max(input,
-								  axis_x) + 1,
-						&maximum) |
-		       touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
-						input_abs_get_fuzz(input, axis_x),
-						&fuzz);
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-x",
+						 input_abs_get_max(input,
+								   axis_x) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
+						 input_abs_get_fuzz(input, axis_x),
+						 &fuzz);
 	if (data_present)
 		touchscreen_set_params(input, axis_x, minimum, maximum - 1, fuzz);
 
 	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-y",
 						input_abs_get_min(input, axis_y),
-						&minimum) |
-		       touchscreen_get_prop_u32(dev, "touchscreen-size-y",
-						input_abs_get_max(input,
-								  axis_y) + 1,
-						&maximum) |
-		       touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
-						input_abs_get_fuzz(input, axis_y),
-						&fuzz);
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-y",
+						 input_abs_get_max(input,
+								   axis_y) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
+						 input_abs_get_fuzz(input, axis_y),
+						 &fuzz);
 	if (data_present)
 		touchscreen_set_params(input, axis_y, minimum, maximum - 1, fuzz);
 
@@ -108,11 +108,11 @@  void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 	data_present = touchscreen_get_prop_u32(dev,
 						"touchscreen-max-pressure",
 						input_abs_get_max(input, axis),
-						&maximum) |
-		       touchscreen_get_prop_u32(dev,
-						"touchscreen-fuzz-pressure",
-						input_abs_get_fuzz(input, axis),
-						&fuzz);
+						&maximum);
+	data_present |= touchscreen_get_prop_u32(dev,
+						 "touchscreen-fuzz-pressure",
+						 input_abs_get_fuzz(input, axis),
+						 &fuzz);
 	if (data_present)
 		touchscreen_set_params(input, axis, 0, maximum, fuzz);