[PATCH 3/4] drm/dsi: Make mipi_dsi_dcs_{read,write}() symmetrical

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

Currently the mipi_dsi_dcs_write() function requires the DCS command
byte to be embedded within the write buffer whereas mipi_dsi_dcs_read()
has a separate parameter. Make them more symmetrical by adding an extra
command parameter to mipi_dsi_dcs_write().

Also update the S6E8AA0 panel driver (the only user of this API) to
adapt to this new API.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/gpu/drm/drm_mipi_dsi.c        | 45 ++++++++++++++++++++++++-----------
 drivers/gpu/drm/panel/panel-s6e8aa0.c |  4 ++--
 include/drm/drm_mipi_dsi.h            |  4 ++--
 3 files changed, 35 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 6aa6a9e95570..bbab06ef80c9 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -201,29 +201,41 @@ EXPORT_SYMBOL(mipi_dsi_detach);
 /**
  * mipi_dsi_dcs_write - send DCS write command
  * @dsi: DSI device
- * @data: pointer to the command followed by parameters
- * @len: length of @data
+ * @cmd: DCS command
+ * @data: pointer to the command payload
+ * @len: payload length
  */
-ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
-			    size_t len)
+ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
+			   const void *data, size_t len)
 {
 	const struct mipi_dsi_host_ops *ops = dsi->host->ops;
-	struct mipi_dsi_msg msg = {
-		.channel = dsi->channel,
-		.tx_buf = data,
-		.tx_len = len
-	};
+	struct mipi_dsi_msg msg;
+	ssize_t err;
+	u8 *tx;
 
 	if (!ops || !ops->transfer)
 		return -ENOSYS;
 
+	if (len > 0) {
+		tx = kmalloc(1 + len, GFP_KERNEL);
+		if (!tx)
+			return -ENOMEM;
+
+		tx[0] = cmd;
+		memcpy(tx + 1, data, len);
+	} else {
+		tx = &cmd;
+	}
+
+	msg.channel = dsi->channel;
+	msg.tx_len = 1 + len;
+	msg.tx_buf = tx;
+
 	switch (len) {
 	case 0:
-		return -EINVAL;
-	case 1:
 		msg.type = MIPI_DSI_DCS_SHORT_WRITE;
 		break;
-	case 2:
+	case 1:
 		msg.type = MIPI_DSI_DCS_SHORT_WRITE_PARAM;
 		break;
 	default:
@@ -231,14 +243,19 @@ ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
 		break;
 	}
 
-	return ops->transfer(dsi->host, &msg);
+	err = ops->transfer(dsi->host, &msg);
+
+	if (len > 0)
+		kfree(tx);
+
+	return err;
 }
 EXPORT_SYMBOL(mipi_dsi_dcs_write);
 
 /**
  * mipi_dsi_dcs_read - send DCS read request command
  * @dsi: DSI device
- * @cmd: DCS read command
+ * @cmd: DCS command
  * @data: pointer to read buffer
  * @len: length of @data
  *
diff --git a/drivers/gpu/drm/panel/panel-s6e8aa0.c b/drivers/gpu/drm/panel/panel-s6e8aa0.c
index 5502ef6bc074..d39bee36816c 100644
--- a/drivers/gpu/drm/panel/panel-s6e8aa0.c
+++ b/drivers/gpu/drm/panel/panel-s6e8aa0.c
@@ -130,7 +130,7 @@ static int s6e8aa0_clear_error(struct s6e8aa0 *ctx)
 	return ret;
 }
 
-static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const void *data, size_t len)
+static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const u8 *data, size_t len)
 {
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
 	ssize_t ret;
@@ -138,7 +138,7 @@ static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const void *data, size_t len)
 	if (ctx->error < 0)
 		return;
 
-	ret = mipi_dsi_dcs_write(dsi, data, len);
+	ret = mipi_dsi_dcs_write(dsi, data[0], data + 1, len - 1);
 	if (ret < 0) {
 		dev_err(ctx->dev, "error %zd writing dcs seq: %*ph\n", ret, len,
 			data);
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 7b5e1a9244e1..bea181121e8b 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -127,8 +127,8 @@ struct mipi_dsi_device {
 
 int mipi_dsi_attach(struct mipi_dsi_device *dsi);
 int mipi_dsi_detach(struct mipi_dsi_device *dsi);
-ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
-			    size_t len);
+ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
+			   const void *data, size_t len);
 ssize_t mipi_dsi_dcs_read(struct mipi_dsi_device *dsi, u8 cmd, void *data,
 			  size_t len);
 
-- 
2.0.1