[PATCH v2 1/8] drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_dcs_write_seq()

[Douglas Anderson]

The mipi_dsi_dcs_write_seq() macro makes a call to
mipi_dsi_dcs_write_buffer() which returns a type ssize_t. The macro
then stores it in an int and checks to see if it's negative. This
could theoretically be a problem if "ssize_t" is larger than "int".

To see the issue, imagine that "ssize_t" is 32-bits and "int" is
16-bits, you could see a problem if there was some code out there that
looked like:

  mipi_dsi_dcs_write_seq(dsi, cmd, <32767 bytes as arguments>);

...since we'd get back that 32768 bytes were transferred and 32768
stored in a 16-bit int would look negative.

Though there are no callsites where we'd actually hit this (even if
"int" was only 16-bit), it's cleaner to make the types match so let's
fix it.

Fixes: 2a9e9daf7523 ("drm/mipi-dsi: Introduce mipi_dsi_dcs_write_seq macro")
Signed-off-by: Douglas Anderson <dianders at chromium.org>
---

Changes in v2:
- New

 include/drm/drm_mipi_dsi.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 82b1cc434ea3..b3576be22bfa 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -337,12 +337,12 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
 	do {                                                               \
 		static const u8 d[] = { cmd, seq };                        \
 		struct device *dev = &dsi->dev;                            \
-		int ret;                                                   \
+		ssize_t 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);                                 \
+				cmd, (int)ret);                            \
 			return ret;                                        \
 		}                                                          \
 	} while (0)
-- 
2.44.0.769.g3c40516874-goog