[PATCH] input/misc/drv260x: Remove a useless comparison

[PATCH] input/misc/drv260x: Remove a useless comparison

[ChenTao]

Fix the following warning:

'mode' and 'library' are u32, they are never be negative,
DRV260X_LRA_MODE and DRV260X_LIB_EMPTY are 0x00, the comparison
is always false.

drivers/input/misc/drv260x.c:478:20: warning:
comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (haptics->mode < DRV260X_LRA_MODE ||
drivers/input/misc/drv260x.c:490:23: warning:
comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (haptics->library < DRV260X_LIB_EMPTY ||

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: ChenTao <chentao107@huawei.com>
---
 drivers/input/misc/drv260x.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/input/misc/drv260x.c b/drivers/input/misc/drv260x.c
index 79d7fa710a71..0078f742df5c 100644
--- a/drivers/input/misc/drv260x.c
+++ b/drivers/input/misc/drv260x.c
@@ -475,8 +475,7 @@ static int drv260x_probe(struct i2c_client *client,
 		return error;
 	}
 
-	if (haptics->mode < DRV260X_LRA_MODE ||
-	    haptics->mode > DRV260X_ERM_MODE) {
+	if (haptics->mode > DRV260X_ERM_MODE) {
 		dev_err(dev, "Vibrator mode is invalid: %i\n", haptics->mode);
 		return -EINVAL;
 	}
@@ -487,8 +486,7 @@ static int drv260x_probe(struct i2c_client *client,
 		return error;
 	}
 
-	if (haptics->library < DRV260X_LIB_EMPTY ||
-	    haptics->library > DRV260X_ERM_LIB_F) {
+	if (haptics->library > DRV260X_ERM_LIB_F) {
 		dev_err(dev,
 			"Library value is invalid: %i\n", haptics->library);
 		return -EINVAL;
-- 
2.22.0

Re: [PATCH] input/misc/drv260x: Remove a useless comparison

[Dmitry Torokhov]

Hi,

On Thu, May 07, 2020 at 01:16:17PM +0800, ChenTao wrote:
> Fix the following warning:
> 
> 'mode' and 'library' are u32, they are never be negative,
> DRV260X_LRA_MODE and DRV260X_LIB_EMPTY are 0x00, the comparison
> is always false.


The fact that the symbolic names resolve to 0 is just a happenstance. We
should not be writing code based on concrete values in this case. I
wish we could tell the compiler to ignore this kind of cases, where we
want to test a range of values, and do not care about concrete numeric
bounds of said range.

> 
> drivers/input/misc/drv260x.c:478:20: warning:
> comparison of unsigned expression < 0 is always false [-Wtype-limits]
>   if (haptics->mode < DRV260X_LRA_MODE ||
> drivers/input/misc/drv260x.c:490:23: warning:
> comparison of unsigned expression < 0 is always false [-Wtype-limits]
>   if (haptics->library < DRV260X_LIB_EMPTY ||

Are we planning on enabling this warning in kernel by default?

Thanks.

-- 
Dmitry