From: Stefani Seibold <stefani@xxxxxxxxxxx>
Most USB devices can only used in a single usage mode. This patch prevents a
reopening on an already opened device.
Signed-off-by: Stefani Seibold <stefani@xxxxxxxxxxx>
---
drivers/usb/usb-skeleton.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 551fb51..456c9a8 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -59,6 +59,7 @@ struct usb_skel {
__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
int errors; /* the last request tanked */
bool ongoing_read; /* a read is going on */
+ bool in_use; /* in use flag */
spinlock_t err_lock; /* lock for errors */
struct kref kref;
struct mutex io_mutex; /* synchronize I/O with disconnect */
@@ -92,17 +93,28 @@ static int skel_open(struct inode *inode, struct file *file)
if (!dev)
return -ENODEV;
+ mutex_lock(&dev->io_mutex);
+ if (dev->in_use) {
+ mutex_unlock(&dev->io_mutex);
+ return -EBUSY;
+ }
+
/*
* must be not locked since a disconnect waits in usb_deregister_dev()
* due the already locked minor_rwsem in the usb_open() function
*/
retval = usb_autopm_get_interface(interface);
- if (!retval)
+ if (!retval) {
+ mutex_unlock(&dev->io_mutex);
return retval;
+ }
/* increment our usage count for the device */
kref_get(&dev->kref);
+ dev->in_use = true;
+ mutex_unlock(&dev->io_mutex);
+
/* save our object in the file's private structure */
file->private_data = dev;
@@ -117,6 +129,7 @@ static int skel_release(struct inode *inode, struct file *file)
mutex_lock(&dev->io_mutex);
if (dev->interface)
usb_autopm_put_interface(dev->interface);
+ dev->in_use = false;
mutex_unlock(&dev->io_mutex);
/* decrement the count on our device */
@@ -517,6 +530,7 @@ static int skel_probe(struct usb_interface *interface,
dev->udev = usb_get_dev(interface_to_usbdev(interface));
dev->interface = interface;
+ dev->in_use = false;
/* set up the endpoint information */
/* use only the first bulk-in and bulk-out endpoints */
--
1.7.8.6
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