[PATCH 03/15] drm/dsi: Add mipi_dsi_set_maximum_return_packet_size() helper

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

From: YoungJun Cho <yj44.cho@samsung.com>

This function can be used to set the maximum return packet size for a
MIPI DSI peripheral.

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
[treding: endianess, kerneldoc, return value]
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 30 ++++++++++++++++++++++++++++++
 include/drm/drm_mipi_dsi.h     |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 1702ffd07986..27fc6dac5e4a 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -198,6 +198,36 @@ int mipi_dsi_detach(struct mipi_dsi_device *dsi)
 }
 EXPORT_SYMBOL(mipi_dsi_detach);
 
+/*
+ * mipi_dsi_set_maximum_return_packet_size() - specify the maximum size of the
+ *    the payload in a long packet transmitted from the peripheral back to the
+ *    host processor
+ * @dsi: DSI peripheral device
+ * @value: the maximum size of the payload
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
+					    u16 value)
+{
+	u8 tx[2] = { value & 0xff, value >> 8 };
+	struct mipi_dsi_msg msg;
+	ssize_t err;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.channel = dsi->channel;
+	msg.type = MIPI_DSI_SET_MAXIMUM_RETURN_PACKET_SIZE;
+	msg.tx_len = sizeof(tx);
+	msg.tx_buf = tx;
+
+	err = dsi->host->ops->transfer(dsi->host, &msg);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_set_maximum_return_packet_size);
+
 /**
  * mipi_dsi_dcs_write_buffer() - transmit a DCS command with payload
  * @dsi: DSI peripheral device
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 836cc2b677d0..ef50b5d0de57 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -132,6 +132,8 @@ static inline struct mipi_dsi_device *to_mipi_dsi_device(struct device *dev)
 
 int mipi_dsi_attach(struct mipi_dsi_device *dsi);
 int mipi_dsi_detach(struct mipi_dsi_device *dsi);
+int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
+					    u16 value);
 ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
 				  const void *data, size_t len);
 ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
-- 
2.1.2