drm/panel: novatek-nt35560: Fix invalid return value

[ Upstream commit 125459e19ec654924e472f3ff5aeea40358dbebf ]

Fix bug in nt35560_set_brightness() which causes the function to
erroneously report an error. mipi_dsi_dcs_write() returns either a
negative value when an error occurred or a positive number of bytes
written when no error occurred. The buggy code reports an error under
either condition.

Fixes: 8152c2bfd780 ("drm/panel: Add driver for Sony ACX424AKP panel")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Brigham Campbell <me@brighamcampbell.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250731032343.1258366-2-me@brighamcampbell.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/panel/panel-novatek-nt35560.c b/drivers/gpu/drm/panel/panel-novatek-nt35560.c
index cc7f96d70826322475b4a2345d8cf96608431dff..52df7e776fae0008fc60f19f292f1fd3f50a4dd1 100644 (file)
--- a/drivers/gpu/drm/panel/panel-novatek-nt35560.c
+++ b/drivers/gpu/drm/panel/panel-novatek-nt35560.c
@@ -162,7 +162,7 @@ static int nt35560_set_brightness(struct backlight_device *bl)
                par = 0x00;
                ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_WRITE_CONTROL_DISPLAY,
                                         &par, 1);
-               if (ret) {
+               if (ret < 0) {
                        dev_err(nt->dev, "failed to disable display backlight (%d)\n", ret);
                        return ret;
                }