Re: [PATCH v1 09/11] leds: aw200xx: improve autodim calculation method

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On 10/9/23 17:02, Dmitry Rokosov wrote:
On Mon, Oct 09, 2023 at 04:18:08PM +0300, Dmitry Rokosov wrote:
On Fri, Oct 06, 2023 at 09:03:47PM +0300, Andy Shevchenko wrote:
On Fri, Oct 6, 2023 at 7:05 PM Dmitry Rokosov
<ddrokosov@xxxxxxxxxxxxxxxxx> wrote:

From: George Stark <gnstark@xxxxxxxxxxxxxxxxx>

use DIV_ROUND_UP instead of coarse div

Please, respect English grammar and punctuation.
Refer to macros and functions as func() (note the parentheses).

...

  #define AW200XX_REG_DIM2FADE(x) ((x) + 1)
+#define AW200XX_REG_FADE2DIM(fade) \
+       DIV_ROUND_UP((fade) * AW200XX_DIM_MAX, AW200XX_FADE_MAX)

Have you checked if the overflow is _now_ possible (compiling on
32-bit platforms as well)?

I suppose we shouldn't carry on about overflow here because the value of
fade cannot exceed 255, and DIM_MAX is set at 63

You can find maximum values of fade and dim in the aw200xx driver
header:

#define AW200XX_DIM_MAX                  (BIT(6) - 1)
#define AW200XX_FADE_MAX                 (BIT(8) - 1)

I agree that checking if the fade is not greater than FADE_MAX will not
be excessive. The LED subsystem is capable of sending brightness levels
higher than 255


Probably we should set max_brightness to AW200XX_FADE_MAX in led_classdev when adding leds.

--
Best regards
George




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