[PATCH v2 2/2] backlight: Add Kinetic KTD2801 driver

[Linus Walleij]

Hi Duje,

thanks for your patch!

On Thu, Jan 18, 2024 at 6:33 PM Duje Mihanović <duje.mihanovic at skole.hr> wrote:

> Add driver for the Kinetic KTD2801 backlight driver.>
> Signed-off-by: Duje Mihanović <duje.mihanovic at skole.hr>

Add some commit message?

> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/of.h>

I don't think you need <linux/of.h>, the compatible table works without
that (is in the device driver core).

> +/* These values have been extracted from Samsung's driver. */
> +#define KTD2801_EXPRESSWIRE_DETECT_DELAY_US    150
> +#define KTD2801_EXPRESSWIRE_DETECT_US          270
> +#define KTD2801_LOW_BIT_HIGH_TIME_US           5
> +#define KTD2801_LOW_BIT_LOW_TIME_US            (4 * KTD2801_HIGH_BIT_LOW_TIME_US)
> +#define KTD2801_HIGH_BIT_LOW_TIME_US           5
> +#define KTD2801_HIGH_BIT_HIGH_TIME_US          (4 * KTD2801_HIGH_BIT_LOW_TIME_US)
> +#define KTD2801_DATA_START_US                  5
> +#define KTD2801_END_OF_DATA_LOW_US             10
> +#define KTD2801_END_OF_DATA_HIGH_US            350
> +#define KTD2801_PWR_DOWN_DELAY_US              2600
> +
> +#define KTD2801_DEFAULT_BRIGHTNESS     100
> +#define KTD2801_MAX_BRIGHTNESS         255
> +
> +struct ktd2801_backlight {
> +       struct backlight_device *bd;
> +       struct gpio_desc *gpiod;
> +       bool was_on;
> +};
> +
> +static int ktd2801_update_status(struct backlight_device *bd)
> +{
> +       struct ktd2801_backlight *ktd2801 = bl_get_data(bd);
> +       u8 brightness = (u8) backlight_get_brightness(bd);
> +
> +       if (backlight_is_blank(bd)) {
> +               gpiod_set_value(ktd2801->gpiod, 0);
> +               udelay(KTD2801_PWR_DOWN_DELAY_US);

That's 2600 us, a pretty long delay in a hard loop or delay timer!

Can you use usleep_range() instead, at least for this one?

> +       for (int i = 0; i < 8; i++) {
> +               u8 next_bit = (brightness & 0x80) >> 7;

I would just:

#include <linux/bits.h>

bool next_bit = !!(brightness & BIT(7));

Yours,
Linus Walleij