[PATCH v2 2/8] drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_generic_write_seq()

[Douglas Anderson]

The mipi_dsi_generic_write_seq() macro makes a call to
mipi_dsi_generic_write() 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_generic_write_seq(dsi, <32768 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: a9015ce59320 ("drm/mipi-dsi: Add a 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 b3576be22bfa..5de2bd62448b 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -318,11 +318,11 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
 	do {                                                                   \
 		static const u8 d[] = { seq };                                 \
 		struct device *dev = &dsi->dev;                                \
-		int ret;                                                       \
+		ssize_t ret;                                                   \
 		ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d));           \
 		if (ret < 0) {                                                 \
 			dev_err_ratelimited(dev, "transmit data failed: %d\n", \
-					    ret);                              \
+					    (int)ret);                         \
 			return ret;                                            \
 		}                                                              \
 	} while (0)
-- 
2.44.0.769.g3c40516874-goog