Re: [PATCH v4 04/79] drm_mode.h: use __u32 and __u64 from linux/types.h

Hi Alex,

On 15 October 2015 at 14:48, Mikko Rapeli [off-list ref] wrote:

On Thu, Oct 15, 2015 at 09:32:10AM -0400, Alex Deucher wrote:

quoted

On Thu, Oct 15, 2015 at 1:55 AM, Mikko Rapeli [off-list ref] wrote:

quoted

Fixes userspace compilation error:

drm/drm_mode.h:472:2: error: unknown type name ‘uint32_t’

Signed-off-by: Mikko Rapeli <redacted>

NACK on all these type conversions.  This has not been a problem for
years and years and the result looks terrible.

Documentation/CodingStyle, section 5

 (e) Types safe for use in userspace.

     In certain structures which are visible to userspace, we cannot
     require C99 types and cannot use the 'u32' form above. Thus, we
     use __u32 and similar types in all structures which are shared
     with userspace.

I have only been looking at kernel headers from userspace occationally in
the past 10 years and had a several cases where the provided headers did
not compile when included into trivial programs trying to use the structs
for an ioctl() for example. This long lasting problem triggered me to write
a test for this and provide these fixes too. In previous reviews usage
of <stdint.h> and its types in kernel headers was already NACK'ed
so I changed several places from uint32_t's to __u32.

With these changes it is btw trivial now to add a grep test the there
are no uint32_t's in include/uapi/ anymore, thus enforcing that coding style
rule.

Based of the reply from Mikko, can you please elaborate your concern ?
Are you thinking about some corner case where this may cause breakage,
or it's solely on stylistic point of view ?

Over the last few years we've been doing some ad-hoc 'synchronisation'
with the headers in libdrm, and this will get us one step closer to
doing things properly.

Fwiw I fully support these changes, as does Gustavo for exynos and Rob for msm.
Reviewed-by: Emil Velikov <redacted>

Thanks
Emil