USB: CDC WDM driver doesn't support non-blocking reads

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>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 8c64c01..3e564bf 100644 (file)
--- 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;
 }