select: add poll_select_set_timeout() and poll_select_copy_remaining() helpers

This patch adds 2 helpers that will be used for the hrtimer based select/poll:

poll_select_set_timeout() is a helper that takes a timeout (as a second, nanosecond
pair) and turns that into a "struct timespec" that represents the absolute end time.
This is a common operation in the many select() and poll() variants and needs various,
common, sanity checks.

poll_select_copy_remaining() is a helper that takes care of copying the remaining
time to userspace, as select(), pselect() and ppoll() do. This function comes in
both a natural and a compat implementation (due to datastructure differences).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/poll.h b/include/linux/poll.h
index ef453828877a..f65de5128a9e 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -120,6 +120,8 @@ extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                            fd_set __user *exp, s64 *timeout);
 
+extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);
+
 #endif /* KERNEL */
 
 #endif /* _LINUX_POLL_H */