Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

Linus Torvalds
2007-04-26T15:56:11Z

On Thu, 26 Apr 2007, Pavel Machek wrote:
>
> #define SNAPSHOT_ATOMIC_SNAPSHOT _IOW(SNAPSHOT_IOC_MAGIC, 3, void *)
> #define SNAPSHOT_SET_IMAGE_SIZE _IOW(SNAPSHOT_IOC_MAGIC, 6, unsigned long)
> #define SNAPSHOT_AVAIL_SWAP _IOR(SNAPSHOT_IOC_MAGIC, 7, void *)
> #define SNAPSHOT_GET_SWAP_PAGE _IOR(SNAPSHOT_IOC_MAGIC, 8, void *)
> #define SNAPSHOT_SET_SWAP_FILE _IOW(SNAPSHOT_IOC_MAGIC, 10, unsigned int)
> #define SNAPSHOT_PMOPS _IOW(SNAPSHOT_IOC_MAGIC, 12, unsigned int)
>
> Are these a problem? Do we need to just use u32 as a argument to keep
> ioctl numbers same between 32 and 64bit versions?

No, you need to use the *proper* type as an argument, and assuming that
type has the same representation in both 32-bit and 64-bit world, the
numbers will automatically match.

Using "void *" is totally bogus. It's supposed to be the actual argument
you pass in, not the pointer to it. If your argument doesn't have a
"struct xyz" kind of format, then you could use "int" (or u32 or
something: but realistically int is 32-bit for the forseeable future), but
it's always wrong to pass in "void *" or "unsigned long", since either of
those are just a sign of the interface being either (a) misunderstood or
(b) broken.

Linus