[PATCH v2] Input: edt-ft5x06 - use U16_MAX instead of -1

[PATCH v2] Input: edt-ft5x06 - use U16_MAX instead of -1

[Andy Shevchenko]

Explicitly show what the value we supply for the touchscreen resolution
when it can't be detected. -1 is hard to compare with when unsigned short
type is in use. The change will help to avoid signed vs. unsigned error
prone comparisons.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
v2: rebased on top of v5.10-rc1
 drivers/input/touchscreen/edt-ft5x06.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
index 6ff81d48da86..34e9cb9c0691 100644
--- a/drivers/input/touchscreen/edt-ft5x06.c
+++ b/drivers/input/touchscreen/edt-ft5x06.c
@@ -23,6 +23,7 @@
 #include <linux/input/touchscreen.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>
+#include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/ratelimit.h>
 #include <linux/regulator/consumer.h>
@@ -1005,8 +1006,8 @@ edt_ft5x06_ts_get_parameters(struct edt_ft5x06_ts_data *tsdata)
 		tsdata->num_y = edt_ft5x06_register_read(tsdata,
 							 reg_addr->reg_num_y);
 	} else {
-		tsdata->num_x = -1;
-		tsdata->num_y = -1;
+		tsdata->num_x = U16_MAX;
+		tsdata->num_y = U16_MAX;
 	}
 }
 
-- 
2.28.0

Re: [PATCH v2] Input: edt-ft5x06 - use U16_MAX instead of -1

[Andy Shevchenko]

On Mon, Oct 26, 2020 at 07:41:26PM +0200, Andy Shevchenko wrote:
> Explicitly show what the value we supply for the touchscreen resolution
> when it can't be detected. -1 is hard to compare with when unsigned short
> type is in use. The change will help to avoid signed vs. unsigned error
> prone comparisons.

Any comments on this?


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] Input: edt-ft5x06 - use U16_MAX instead of -1

[Dmitry Torokhov]

Hi Andy,

On Mon, Oct 26, 2020 at 07:41:26PM +0200, Andy Shevchenko wrote:
> Explicitly show what the value we supply for the touchscreen resolution
> when it can't be detected. -1 is hard to compare with when unsigned short
> type is in use. The change will help to avoid signed vs. unsigned error
> prone comparisons.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> v2: rebased on top of v5.10-rc1
>  drivers/input/touchscreen/edt-ft5x06.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
> index 6ff81d48da86..34e9cb9c0691 100644
> --- a/drivers/input/touchscreen/edt-ft5x06.c
> +++ b/drivers/input/touchscreen/edt-ft5x06.c
> @@ -23,6 +23,7 @@
>  #include <linux/input/touchscreen.h>
>  #include <linux/irq.h>
>  #include <linux/kernel.h>
> +#include <linux/limits.h>
>  #include <linux/module.h>
>  #include <linux/ratelimit.h>
>  #include <linux/regulator/consumer.h>
> @@ -1005,8 +1006,8 @@ edt_ft5x06_ts_get_parameters(struct edt_ft5x06_ts_data *tsdata)
>  		tsdata->num_y = edt_ft5x06_register_read(tsdata,
>  							 reg_addr->reg_num_y);
>  	} else {
> -		tsdata->num_x = -1;
> -		tsdata->num_y = -1;
> +		tsdata->num_x = U16_MAX;
> +		tsdata->num_y = U16_MAX;

Here we do not really do any comparisons, and using -1 to set to
maximum unsigned number is a common pattern...

However I just CCed you on a patch that removes special handling for
number of electrodes on select firmwares, so this patch will no longer
be relevant.

Thanks.

-- 
Dmitry