Non blocking IO is supported in the read path of usb-skeleton.
This is done by just not blocking. As support for handling signals
without stopping IO is already there, it can be used for O_NONBLOCK, too.
Signed-off-by: Oliver Neukum <oliver@xxxxxxxxxx>
--
commit 5dab1a11bc706d1bd087b63d705db98e8c1913d2
Author: Oliver Neukum <oliver@xxxxxxxxxx>
Date: Wed Sep 9 14:23:52 2009 +0200
usb:usb-skeleton: nonblocking IO in the read path
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 7441df2..ef8c877 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -268,6 +268,11 @@ retry:
spin_unlock_irq(&dev->err_lock);
if (ongoing_io) {
+ /* nonblocking IO shall not wait */
+ if (file->f_flags & O_NONBLOCK) {
+ rv = -EAGAIN;
+ goto exit;
+ }
/*
* IO may take forever
* hence wait in an interruptible state
@@ -351,8 +356,9 @@ retry:
rv = skel_do_read_io(dev, count);
if (rv < 0)
goto exit;
- else
- goto retry;
+ else if (!file->f_flags & O_NONBLOCK)
+ goto retry;
+ rv = -EAGAIN;
}
exit:
mutex_unlock(&dev->io_mutex);
--
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