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Subject[043/136] USB: CDC WDM driver doesnt support non-blocking reads
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Oliver Neukum <oliver@neukum.org>

commit 7f1dc313d01f5f0f84c06051343a3b8623932d3c upstream.

support for O_NONBLOCK in read and write path
by simply not waiting for data in read or availability
of the write urb in write but returning -EAGAIN

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/usb/class/cdc-wdm.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)

--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -313,8 +313,13 @@ static ssize_t wdm_write
r = usb_autopm_get_interface(desc->intf);
if (r < 0)
goto outnp;
- r = wait_event_interruptible(desc->wait, !test_bit(WDM_IN_USE,
- &desc->flags));
+
+ if (!file->f_flags && O_NONBLOCK)
+ r = wait_event_interruptible(desc->wait, !test_bit(WDM_IN_USE,
+ &desc->flags));
+ else
+ if (test_bit(WDM_IN_USE, &desc->flags))
+ r = -EAGAIN;
if (r < 0)
goto out;

@@ -377,7 +382,7 @@ outnl:
static ssize_t wdm_read
(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
{
- int rv, cntr;
+ int rv, cntr = 0;
int i = 0;
struct wdm_device *desc = file->private_data;

@@ -389,10 +394,23 @@ static ssize_t wdm_read
if (desc->length == 0) {
desc->read = 0;
retry:
+ if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+ rv = -ENODEV;
+ goto err;
+ }
i++;
- rv = wait_event_interruptible(desc->wait,
- test_bit(WDM_READ, &desc->flags));
+ if (file->f_flags & O_NONBLOCK) {
+ if (!test_bit(WDM_READ, &desc->flags)) {
+ rv = cntr ? cntr : -EAGAIN;
+ goto err;
+ }
+ rv = 0;
+ } else {
+ rv = wait_event_interruptible(desc->wait,
+ test_bit(WDM_READ, &desc->flags));
+ }

+ /* may have happened while we slept */
if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
rv = -ENODEV;
goto err;
@@ -448,7 +466,7 @@ retry:

err:
mutex_unlock(&desc->rlock);
- if (rv < 0)
+ if (rv < 0 && rv != -EAGAIN)
dev_err(&desc->intf->dev, "wdm_read: exit error\n");
return rv;
}



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