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 <[email protected]>
---
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
On Sat, 27 Apr 2024 at 02:59, Douglas Anderson <[email protected]> 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 <[email protected]>
> ---
>
> 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
On Sat, Apr 27, 2024 at 04:44:33AM +0300, Dmitry Baryshkov wrote:
> On Sat, 27 Apr 2024 at 02:59, Douglas Anderson <[email protected]> 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 <[email protected]>
> > ---
> >
> > 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
Hi Douglas,
please consider the above for all the pathces, there are more places
where a cast can be dropped.
Sam
Hi,
On Fri, Apr 26, 2024 at 11:22 PM Sam Ravnborg <[email protected]> wrote:
>
> On Sat, Apr 27, 2024 at 04:44:33AM +0300, Dmitry Baryshkov wrote:
> > On Sat, 27 Apr 2024 at 02:59, Douglas Anderson <[email protected]> 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 <[email protected]>
> > > ---
> > >
> > > 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
>
> Hi Douglas,
> please consider the above for all the pathces, there are more places
> where a cast can be dropped.
Sure, I'll change in the next version. I personally prefer the %d with
an "int" type because technically we're printing an error code and
errors are int-sized. ...but I don't feel strongly and I guess there's
a tiny chance some bug in the code could lead to a negative value
that's more useful as 64-bits than 32-bits. ;-)
I will note that I will still need a cast in some of the later patches
for "%*ph" since, I believe, the size passed for the "*" in a printf
format string is defined to be an int, not a size_t or ssize_t.
-Doug