On Wed, Sep 12, 2018 at 05:01:02PM +0200, Arnd Bergmann wrote: > Many drivers have ioctl() handlers that are completely compatible > between 32-bit and 64-bit architectures, except for the argument > that is passed down from user space and may have to be passed > through compat_ptr() in order to become a valid 64-bit pointer. > > Using ".compat_ptr=generic_compat_ioctl_ptrarg" in file operations > should let us simplify a lot of those drivers to avoid #ifdef > checks, and convert additional drivers that don't have proper > compat handling yet. Just keep in mind that this should *only* be used when all ioctls implemented in a given instance do take pointers. Because otherwise you are asking for trouble - e.g. if one of them takes an u32 used as a bitmap, this will run into trouble as soon as somebody uses bit 31. With no visible warnings. IOW, it shouldn't be used blindly and it should come with big fat warning.
