Fill the spefified area with zeros.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Useful for debugging purposes.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

iov_to_buf() has an 'offset' parameter, iov_from_buf() hasn't.
This patch adds the missing parameter to iov_from_buf().
It also renames the 'offset' parameter to 'iov_off' to
emphasize it's the offset into the iovec and not the buffer.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Acked-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

The iov functions can be useful to other code as well.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
CC: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

iov_to_buf() puts the buffer contents in the iov in a linearized buffer.

iov_size() gets the length of the contents in the iov.

The iov_to_buf() function is the memcpy_to_iovec() function that was
used in virtio-ballon.c.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

The virtio-net code uses iov_fill() which fills an iov from a linear
buffer. The virtio-serial-bus code does something similar in an
open-coded function.

Create a new iov.c file that has iov_from_buf().

Convert virtio-net and virtio-serial-bus over to use this functionality.
virtio-net used ints to hold sizes, the new function is going to use
size_t types.

Later commits will add the opposite functionality -- going from an iov
to a linear buffer.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>