From: Philippe Cornu <philippe.cornu@st.com>
Date: Thu, 25 Jan 2018 11:37:59 +0100
Subject: drm/bridge/synopsys: dsi: Add a warning msg on dsi read requests
Git-commit: 4cda6e8e1ea0e7bc80028fa4fe196357a2799d05
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The dcs/generic dsi read feature is not yet implemented so it
is important to warn the host_transfer() caller in case of
read operation requests.

Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180125103800.1999-2-philippe.cornu@st.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -398,6 +398,12 @@ static ssize_t dw_mipi_dsi_host_transfer
 	struct mipi_dsi_packet packet;
 	int ret;
 
+	if (msg->rx_buf || msg->rx_len) {
+		/* TODO dw drv improvements: implement read feature */
+		dev_warn(dsi->dev, "read operations not yet implemented\n");
+		return -EINVAL;
+	}
+
 	ret = mipi_dsi_create_packet(&packet, msg);
 	if (ret) {
 		dev_err(dsi->dev, "failed to create packet: %d\n", ret);