On Sat, 27 Apr 2024 at 02:59, Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxxx>
> ---
>
> 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); \
Please consider using %zd instead
> return ret; \
> } \
> } while (0)
> --
> 2.44.0.769.g3c40516874-goog
>
--
With best wishes
Dmitry
