On Thu, 02 Jun 2016, Vinay Simha BN <simhavcs@xxxxxxxxx> wrote:
> Provide a small convenience wrapper that set/get the
> backlight brightness control and creates the backlight
> device for the panel interface
To be pedantic, we should downplay "backlight" in the DSI DCS brightness
control... there need not be a backlight, at all, for brightness control
(see AMOLED).
> Cc: John Stultz <john.stultz@xxxxxxxxxx>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: Archit Taneja <archit.taneja@xxxxxxxxx>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Signed-off-by: Vinay Simha BN <simhavcs@xxxxxxxxx>
>
> --
> v1:
> *tested in nexus7 2nd gen.
> ---
> drivers/gpu/drm/drm_mipi_dsi.c | 63 ++++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_mipi_dsi.h | 3 ++
> 2 files changed, 66 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 2f0b85c..ac4521e 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -1026,6 +1026,69 @@ int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format)
> }
> EXPORT_SYMBOL(mipi_dsi_dcs_set_pixel_format);
>
> +static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
I'd rather see convenience helpers that are not tied to struct
backlight_device. You can add a one-line wrapper on top that takes
struct backlight_device pointer.
While at it, please name the helpers according to the DCS command.
> +{
> + struct mipi_dsi_device *dsi = bl_get_data(bl);
> + int ret;
> + u8 brightness;
> +
> + dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
> +
> + ret = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
> + &brightness, sizeof(brightness));
> + if (ret < 0)
> + return ret;
> +
> + dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> + return brightness;
> +}
> +
> +static int dsi_dcs_bl_update_status(struct backlight_device *bl)
> +{
> + struct mipi_dsi_device *dsi = bl_get_data(bl);
> + int ret;
> + u8 brightness = bl->props.brightness;
> +
> + dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
> +
> + ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
> + &brightness, sizeof(brightness));
> + if (ret < 0)
> + return ret;
> +
> + dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> + return 0;
> +}
> +
> +static const struct backlight_ops dsi_bl_ops = {
> + .update_status = dsi_dcs_bl_update_status,
> + .get_brightness = dsi_dcs_bl_get_brightness,
> +};
> +
> +/**
> + * drm_panel_create_dsi_backlight() - creates the backlight device for the panel
> + * @dsi: DSI peripheral device
> + *
> + * @return a struct backlight on success, or an ERR_PTR on error
> + */
> +struct backlight_device
> + *drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi)
> +{
> + struct device *dev = &dsi->dev;
> + struct backlight_properties props;
> +
> + memset(&props, 0, sizeof(props));
> + props.type = BACKLIGHT_RAW;
> + props.brightness = 255;
> + props.max_brightness = 255;
The DCS spec says the max is either 0xff or 0xffff depending on the
implementation... this obviously affects the helpers as well.
And how about the backlight bits in write_control_display? I just fear
this is a simplistic view of brightness control on DSI, and this will
grow hairy over time. I think I'd rather see generic DSI DCS brightness
*helpers* in this file, and then *perhaps* a separate file for
brightness control in general.
BR,
Jani.
> +
> + return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
> + &dsi_bl_ops, &props);
> +}
> +EXPORT_SYMBOL(drm_panel_create_dsi_backlight);
> +
> static int mipi_dsi_drv_probe(struct device *dev)
> {
> struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 2788dbe..9dd6a97 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -12,6 +12,7 @@
> #ifndef __DRM_MIPI_DSI_H__
> #define __DRM_MIPI_DSI_H__
>
> +#include <linux/backlight.h>
> #include <linux/device.h>
>
> struct mipi_dsi_host;
> @@ -269,6 +270,8 @@ int mipi_dsi_dcs_set_tear_off(struct mipi_dsi_device *dsi);
> int mipi_dsi_dcs_set_tear_on(struct mipi_dsi_device *dsi,
> enum mipi_dsi_dcs_tear_mode mode);
> int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format);
> +struct backlight_device
> + *drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi);
>
> /**
> * struct mipi_dsi_driver - DSI driver
--
Jani Nikula, Intel Open Source Technology Center
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