tree 2ef5c99a73fe3d9c9ef2e85bdf72d0807b170d5b
parent 1f9dec1e0164b48da9b268a02197f38caa69b118
author David Herrmann <dh.herrmann@googlemail.com> 1339334176 +0200
committer Jiri Kosina <jkosina@suse.cz> 1340019720 +0200

HID: uhid: implement read() on uhid devices

User-space can use read() to get a single event from uhid devices. read()
does never return multiple events. This allows us to extend the event
structure and still keep backwards compatibility.

If user-space wants to get multiple events in one syscall, they should use
the readv()/writev() syscalls which are supported by uhid.

This introduces a new lock which helps us synchronizing simultaneous reads
from user-space. We also correctly return -EINVAL/-EFAULT only on errors
and retry the read() when some other thread captured the event faster than
we did.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>