sparse: ioctl defines and "error: bad integer constant expression"

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi!

Here is another sparse error that I get when running sparse over
drivers/media/v4l2-core/v4l2-ioctl.c:

drivers/media/v4l2-core/v4l2-ioctl.c:2043:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2044:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2045:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2046:9: error: bad integer constant expression

etc.

The root cause of that turns out to be in include/asm-generic/ioctl.h:

#include <uapi/asm-generic/ioctl.h>

/* provoke compile error for invalid uses of size argument */
extern unsigned int __invalid_size_argument_for_IOC;
#define _IOC_TYPECHECK(t) \
        ((sizeof(t) == sizeof(t[1]) && \
          sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
          sizeof(t) : __invalid_size_argument_for_IOC)

If it is defined as this:

#define _IOC_TYPECHECK(t) (sizeof(t))

then all is well with the world.

I can patch v4l2-ioctl.c to redefine _IOC_TYPECHECK if __CHECKER__ is defined, but
shouldn't sparse understand this instead? There was a similar situation with
ARRAY_SIZE in the past that sparse now understands.

Regards,

	Hans