doc: ioctl: Add some clarifications to botching-up-ioctls
- The guide currently says to pad the structure to a multiple of
64-bits. This is not necessary in cases where the structure contains
no 64-bit types. Clarify this concept to avoid unnecessary padding.
- When using __u64 to hold user pointers, blindly trying to do a cast to
a void __user * may generate a warning on 32-bit systems about a cast
from an integer to a pointer of different size. There is a macro to
deal with this which hides an ugly double cast. Add a reference to
this macro.
Signed-off-by: Laura Abbott <labbott@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
1 file changed