drm/mipi-dsi: Introduce mipi_dsi_dcs_write_seq macro

A helper macro that can be used to simplify sending DCS commands.
It is useful in scenarios like panel initialization which can sometimes
involve sending lot of DCS commands.
Signed-off-by: Joel Selvaraj <jo@jsfamily.in>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/BY5PR02MB700952493EEB6F0E77DC8416D9DF9@BY5PR02MB7009.namprd02.prod.outlook.com

include/drm/drm_mipi_dsi.h

@@ -295,6 +295,23 @@ int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
 int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
 					u16 *brightness);
 
+/**
+ * mipi_dsi_dcs_write_seq - transmit a DCS command with payload
+ * @dsi: DSI peripheral device
+ * @cmd: Command
+ * @seq: buffer containing data to be transmitted
+ */
+#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) do {				\
+		static const u8 d[] = { cmd, seq };				\
+		struct device *dev = &dsi->dev;	\
+		int ret;						\
+		ret = mipi_dsi_dcs_write_buffer(dsi, d, ARRAY_SIZE(d));	\
+		if (ret < 0) {						\
+			dev_err_ratelimited(dev, "sending command %#02x failed: %d\n", cmd, ret); \
+			return ret;						\
+		}						\
+	} while (0)
+
 /**
  * struct mipi_dsi_driver - DSI driver
  * @driver: device driver model driver