Re: [RFC] Splitting kernel headers and deprecating __KERNEL__

Andries Brouwer
2004-12-05T02:26:25Z

On Sat, Dec 04, 2004 at 07:49:57PM -0500, Rob Landley wrote:

> How the heck do you implement losetup without including linux/loop.h?

Copy the util-linux sources.

> The way both busybox and util-linux do it is the to block copy out lots of
> ugly crap, include linux/version.h, and have #ifdefs to fix up differences
> between known kernel versions. I'm serious.

Yes, a well-known problem. Util-linux has roughly

#include <linux/posix_types.h>
#include <linux/version.h>

#if LINUX_VERSION_CODE < KERNEL_VERSION(2,5,68)
#define my_dev_t __kernel_dev_t
#else
#define my_dev_t __kernel_old_dev_t
#endif

Here the struct has not changed, but the names for the types have changed.
Thus, instead of looking at <linux/version.h> and <linux/posix_types.h>
one could have a completely kernel-independent source with different defines
for each architecture.

But, all that nonsense is needed only for the obsolete struct loop_info.
Any new program should use struct loop_info64, and it has a clean definition:

struct loop_info64 {
__u64 lo_device; /* ioctl r/o */
__u64 lo_inode; /* ioctl r/o */
__u64 lo_rdevice; /* ioctl r/o */
__u64 lo_offset;
__u64 lo_sizelimit;/* bytes, 0 == max available */
__u32 lo_number; /* ioctl r/o */
__u32 lo_encrypt_type;
__u32 lo_encrypt_key_size; /* ioctl w/o */
__u32 lo_flags; /* ioctl r/o */
__u8 lo_file_name[LO_NAME_SIZE];
__u8 lo_crypt_name[LO_NAME_SIZE];
__u8 lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
__u64 lo_init[2];
};