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Date: Thu, 14 Oct 2021 14:02:43 -0700
From: Nick Desaulniers <ndesaulniers@...gle.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>,
linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: Re: [PATCH] Input: touchscreen - Avoid bitwise vs logical OR warning
On Thu, Oct 14, 2021 at 1:58 PM Nathan Chancellor <nathan@...nel.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@...nel.org>
Thanks for the patch!
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.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
>
>
--
Thanks,
~Nick Desaulniers
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