Extract the no_poll() and vop_nopoll() code into the common routine

poll_no_poll().
Return a poll_no_poll() result from devfs_poll_f() when
filedescriptor does not reference the live cdev, instead of ENXIO.

Noted and tested by:	hps
MFC after:	1 week

1 files changed, 16 insertions, 0 deletions

diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
index 3209610..ad7c32e 100644
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -731,6 +731,22 @@ out:
 	return (error);
 }
 
+int
+poll_no_poll(int events)
+{
+	/*
+	 * Return true for read/write.  If the user asked for something
+	 * special, return POLLNVAL, so that clients have a way of
+	 * determining reliably whether or not the extended
+	 * functionality is present without hard-coding knowledge
+	 * of specific filesystem implementations.
+	 */
+	if (events & ~POLLSTANDARD)
+		return (POLLNVAL);
+
+	return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
+}
+
 #ifndef _SYS_SYSPROTO_H_
 struct select_args {
 	int	nd;