source: GPL/trunk/include/linux/uio.h

/* $Id: uio.h,v 1.1.1.1 2003/07/02 13:57:00 eleph Exp $ */

#ifndef _LINUX_UIO_H
#define _LINUX_UIO_H

#include <linux/types.h>

enum iter_type {
        /* iter types */
        ITER_IOVEC,
        ITER_KVEC,
        ITER_BVEC,
        ITER_XARRAY,
        ITER_DISCARD,
        ITER_UBUF,
};

#define ITER_SOURCE     1       // == WRITE
#define ITER_DEST       0       // == READ

struct kvec {
        void *iov_base; /* and that should *never* hold a userland pointer */
        size_t iov_len;
};

struct iovec {
        char    *iov_base;      /* Base address. */
#ifdef __32BIT__
        size_t   iov_len;       /* Length. */
#else
        long     iov_len;       /* Length. */
#endif
};

struct iov_iter {
        u8 iter_type;
        bool copy_mc;
        bool nofault;
        bool data_source;
        bool user_backed;
        union {
                /*
                 * This really should be a const, but we cannot do that without
                 * also modifying any of the zero-filling iter init functions.
                 * Leave it non-const for now, but it should be treated as such.
                 */
                struct iovec __ubuf_iovec;
                struct {
                        union {
                                /* use iter_iov() to get the current vec */
                                const struct iovec *__iov;
                                void __user *ubuf;
                        };
                        size_t count;
                };
        };
        union {
                const struct iovec *iov;
                const struct kvec *kvec;
                const struct bio_vec *bvec;
        };
        unsigned long nr_segs;
};

static inline bool iter_is_iovec(const struct iov_iter *i)
{
        return !(i->iter_type & (ITER_BVEC | ITER_KVEC));
}

static inline const struct iovec *iter_iov(const struct iov_iter *iter)
{
        if (iter->iter_type == ITER_UBUF)
                return (const struct iovec *) &iter->__ubuf_iovec;
        return iter->__iov;
}
int import_ubuf(int type, void __user *buf, size_t len, struct iov_iter *i);

#endif /* _LINUX_UIO_H */