linux-kernel - Re: [RFC PATCH v3 2/3] drm/panel: sofef00: Use 16-bit brightness function

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Date:   Wed, 18 Jan 2023 10:46:06 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Richard Acayan <mailingradian@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Vinay Simha BN <simhavcs@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Daniel Mentz <danielmentz@...gle.com>,
        Caleb Connolly <caleb@...nolly.tech>
Subject: Re: [RFC PATCH v3 2/3] drm/panel: sofef00: Use 16-bit brightness
 function

On 16/01/2023 23:49, Richard Acayan wrote:
> These panels communicate brightness in big endian. This is not a quirk
> of the panels themselves, but rather, a part of the MIPI standard. Use
> the new mipi_dsi_dcs_set_display_brightness_large() function that
> properly handles 16-bit brightness instead of doing special processing
> of the brightness values.
> 
> Signed-off-by: Richard Acayan <mailingradian@...il.com>
> Tested-by: Caleb Connolly <caleb@...nolly.tech>
> ---
>   drivers/gpu/drm/panel/panel-samsung-sofef00.c | 9 ++-------
>   1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-samsung-sofef00.c b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> index 9db49a028930..1ebb79e3103c 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-sofef00.c
> @@ -10,7 +10,6 @@
>   #include <linux/of.h>
>   #include <linux/of_device.h>
>   #include <linux/regulator/consumer.h>
> -#include <linux/swab.h>
>   #include <linux/backlight.h>
>   
>   #include <video/mipi_display.h>
> @@ -213,13 +212,9 @@ static int sofef00_panel_bl_update_status(struct backlight_device *bl)
>   {
>   	struct mipi_dsi_device *dsi = bl_get_data(bl);
>   	int err;
> -	u16 brightness;
> +	u16 brightness = (u16)backlight_get_brightness(bl);
>   
> -	brightness = (u16)backlight_get_brightness(bl);
> -	// This panel needs the high and low bytes swapped for the brightness value
> -	brightness = __swab16(brightness);
> -
> -	err = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
> +	err = mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
>   	if (err < 0)
>   		return err;
>   

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>