Hi Sam,
On 20-06-2021 15:01, Sam Ravnborg wrote:
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@codeaurora.org Reviewed-by: Douglas Anderson dianders@chromium.org Reviewed-by: Lyude Paul lyude@redhat.com
(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.
The backlight_get_brightness() used above has the backlight_is_blank() check and returns brightness 0 when the backlight_is_blank(bd) is true. So, instead of calling backlight_is_blank(bd), we are checking brightness value here. I took the reference from pwm_backlight_update_status() of the PWM backlight driver (drivers/video/backlight/pwm_bl.c)
Yes, we can change this _if_ condition to use backlight_is_blank(bd), as this is an inline function, and is more meaningful. With this, there would be one change in the behavior of _backlight_update_status function in the following case:
- Setting brightness=0 when the backlight is not blank: In the current case setting brightness=0 is disabling the backlight. In the new case, setting brightness=0 will set the brightness to 0 and will do nothing to backlight disable.
I think that should not be a problem?
I cannot see why you need the extra check on ->enabled? Would it be sufficient to check backlight_is_blank() only?
This extra check on bl->enabled flag is added to avoid enabling/disabling backlight again if it is already enabled/disabled. Using this flag way can know the transition between backlight blank and un-blank, and decide when to enable/disable the backlight.
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
Thanks, Rajeev