Hi Rajeev
On Sat, Jun 19, 2021 at 04:10:26PM +0530, Rajeev Nandan wrote:
> Some panels support backlight control over DP AUX channel using
> VESA's standard backlight control interface.
> Using new DRM eDP backlight helpers, add support to create and
> register a backlight for those panels in drm_panel to simplify
> the panel drivers.
>
> The panel driver with access to "struct drm_dp_aux" can create and
> register a backlight device using following code snippet in its
> probe() function:
>
> err = drm_panel_dp_aux_backlight(panel, aux);
> if (err)
> return err;
IT very good to have this supported by drm_panel, so we avoid
bolierplate in various drivers.
>
> Then drm_panel will handle backlight_(enable|disable) calls
> similar to the case when drm_panel_of_backlight() is used.
>
> Currently, we are not supporting one feature where the source
> device can combine the backlight brightness levels set through
> DP AUX and the BL_PWM_DIM eDP connector pin. Since it's not
> required for the basic backlight controls, it can be added later.
>
> Signed-off-by: Rajeev Nandan <rajeevny@xxxxxxxxxxxxxx>
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
> ---
>
> (no changes since v6)
>
> Changes in v5:
> - New
>
> Changes in v6:
> - Fixed ordering of memory allocation (Douglas)
> - Updated word wrapping in a comment (Douglas)
>
> drivers/gpu/drm/drm_panel.c | 108 ++++++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_panel.h | 15 ++++--
> 2 files changed, 119 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index f634371..9e65342 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -26,12 +26,20 @@
> #include <linux/module.h>
>
> #include <drm/drm_crtc.h>
> +#include <drm/drm_dp_helper.h>
> #include <drm/drm_panel.h>
> #include <drm/drm_print.h>
>
> static DEFINE_MUTEX(panel_lock);
> static LIST_HEAD(panel_list);
>
> +struct dp_aux_backlight {
> + struct backlight_device *base;
> + struct drm_dp_aux *aux;
> + struct drm_edp_backlight_info info;
> + bool enabled;
> +};
> +
> /**
> * DOC: drm panel
> *
> @@ -342,6 +350,106 @@ int drm_panel_of_backlight(struct drm_panel *panel)
> return 0;
> }
> EXPORT_SYMBOL(drm_panel_of_backlight);
> +
> +static int dp_aux_backlight_update_status(struct backlight_device *bd)
> +{
> + struct dp_aux_backlight *bl = bl_get_data(bd);
> + u16 brightness = backlight_get_brightness(bd);
backlight_get_brightness() returns an int, so using u16 seems wrong.
But then drm_edp_backlight_enable() uses u16 for level - so I guess it
is OK.
We use unsigned long, int, u16 for brightness. Looks like something one
could look at one day, but today is not that day.
> + int ret = 0;
> +
> + if (brightness > 0) {
Use backlight_is_blank(bd) here, as this is really what you test for.
I cannot see why you need the extra check on ->enabled?
Would it be sufficient to check backlight_is_blank() only?
> + if (!bl->enabled) {
> + drm_edp_backlight_enable(bl->aux, &bl->info, brightness);
> + bl->enabled = true;
> + return 0;
> + }
> + ret = drm_edp_backlight_set_level(bl->aux, &bl->info, brightness);
> + } else {
> + if (bl->enabled) {
> + drm_edp_backlight_disable(bl->aux, &bl->info);
> + bl->enabled = false;
> + }
> + }
> +
> + return ret;
> +}
Sam
