Re: [PATCH] Input: touchscreen - Avoid bitwise vs logical OR warning

From
Nick Desaulniers <ndesaulniers@google.com>
Date
2021-10-14 21:03:00
Also in
linux-input, lkml
Reply to
Nathan Chancellor, 2021-10-14
On Thu, Oct 14, 2021 at 1:58 PM Nathan Chancellor [off-list ref] 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>
quoted hunk ↗ jump to hunk
---
 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
Thread (2 messages) 2 messages, 2 authors, last reply 2021-10-14
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