drm/dsi: Implement DCS set/get display brightness

Provide a small convenience wrapper that set/get the display brightness.

Cc: John Stultz <[e-mail]>
Cc: Sumit Semwal <[e-mail]>
Cc: Archit Taneja <[e-mail]>
Cc: Rob Clark <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Thierry Reding <[e-mail]>
Cc: Emil Velikov <[e-mail]>
Signed-off-by: Vinay Simha BN <[e-mail]>
Reviewed-by: Emil Velikov <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/drm/drm_mipi_dsi.c

···
 }
 EXPORT_SYMBOL(mipi_dsi_dcs_set_tear_scanline);
 
+/**
+ * mipi_dsi_dcs_set_display_brightness() - sets the brightness value of the
+ *    display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
+					u16 brightness)
+{
+	u8 payload[2] = { brightness & 0xff, brightness >> 8 };
+	ssize_t err;
+
+	err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
+				 payload, sizeof(payload));
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness);
+
+/**
+ * mipi_dsi_dcs_get_display_brightness() - gets the current brightness value
+ *    of the display
+ * @dsi: DSI peripheral device
+ * @brightness: brightness value
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
+					u16 *brightness)
+{
+	ssize_t err;
+
+	err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
+				brightness, sizeof(*brightness));
+	if (err <= 0) {
+		if (err == 0)
+			err = -ENODATA;
+
+		return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);
+
 static int mipi_dsi_drv_probe(struct device *dev)
 {
 	struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);

include/drm/drm_mipi_dsi.h

···
 			     enum mipi_dsi_dcs_tear_mode mode);
 int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format);
 int mipi_dsi_dcs_set_tear_scanline(struct mipi_dsi_device *dsi, u16 scanline);
+int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
+					u16 brightness);
+int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
+					u16 *brightness);
 
 /**
  * struct mipi_dsi_driver - DSI driver