diff options
Diffstat (limited to 'drivers/usb/usb-skeleton.c')
| -rw-r--r-- | drivers/usb/usb-skeleton.c | 41 |
1 files changed, 29 insertions, 12 deletions
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c index 46929a1b6f24..8432bf171d2e 100644 --- a/drivers/usb/usb-skeleton.c +++ b/drivers/usb/usb-skeleton.c @@ -34,18 +34,25 @@ static struct usb_device_id skel_table [] = { }; MODULE_DEVICE_TABLE(usb, skel_table); +/* to prevent a race between open and disconnect */ +static DEFINE_MUTEX(skel_open_lock); + /* Get a minor range for your devices from the usb maintainer */ #define USB_SKEL_MINOR_BASE 192 /* our private defines. if this grows any larger, use your own .h file */ #define MAX_TRANSFER (PAGE_SIZE - 512) +/* MAX_TRANSFER is chosen so that the VM is not stressed by + allocations > PAGE_SIZE and the number of packets in a page + is an integer 512 is the largest possible packet on EHCI */ #define WRITES_IN_FLIGHT 8 +/* arbitrarily chosen */ /* Structure to hold all of our device specific stuff */ struct usb_skel { - struct usb_device *dev; /* the usb device for this device */ - struct usb_interface *interface; /* the interface for this device */ + struct usb_device *udev; /* the usb device for this device */ + struct usb_interface *interface; /* the interface for this device */ struct semaphore limit_sem; /* limiting the number of writes in progress */ unsigned char *bulk_in_buffer; /* the buffer to receive data */ size_t bulk_in_size; /* the size of the receive buffer */ @@ -76,8 +83,10 @@ static int skel_open(struct inode *inode, struct file *file) subminor = iminor(inode); + mutex_lock(&skel_open_lock); interface = usb_find_interface(&skel_driver, subminor); if (!interface) { + mutex_unlock(&skel_open_lock); err ("%s - error, can't find device for minor %d", __FUNCTION__, subminor); retval = -ENODEV; @@ -86,12 +95,15 @@ static int skel_open(struct inode *inode, struct file *file) dev = usb_get_intfdata(interface); if (!dev) { + mutex_unlock(&skel_open_lock); retval = -ENODEV; goto exit; } /* increment our usage count for the device */ kref_get(&dev->kref); + /* now we can drop the lock */ + mutex_unlock(&skel_open_lock); /* prevent the device from being autosuspended */ retval = usb_autopm_get_interface(interface); @@ -201,12 +213,6 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou goto exit; } - mutex_lock(&dev->io_mutex); - if (!dev->interface) { /* disconnect() was called */ - retval = -ENODEV; - goto error; - } - /* create a urb, and a buffer for it, and copy the data to the urb */ urb = usb_alloc_urb(0, GFP_KERNEL); if (!urb) { @@ -225,6 +231,14 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou goto error; } + /* this lock makes sure we don't submit URBs to gone devices */ + mutex_lock(&dev->io_mutex); + if (!dev->interface) { /* disconnect() was called */ + mutex_unlock(&dev->io_mutex); + retval = -ENODEV; + goto error; + } + /* initialize the urb properly */ usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr), @@ -233,6 +247,7 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou /* send the data out the bulk port */ retval = usb_submit_urb(urb, GFP_KERNEL); + mutex_unlock(&dev->io_mutex); if (retval) { err("%s - failed submitting write urb, error %d", __FUNCTION__, retval); goto error; @@ -241,7 +256,7 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou /* release our reference to this urb, the USB core will eventually free it entirely */ usb_free_urb(urb); - mutex_unlock(&dev->io_mutex); + return writesize; error: @@ -249,7 +264,6 @@ error: usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma); usb_free_urb(urb); } - mutex_unlock(&dev->io_mutex); up(&dev->limit_sem); exit: @@ -344,6 +358,7 @@ static int skel_probe(struct usb_interface *interface, const struct usb_device_i error: if (dev) + /* this frees allocated memory */ kref_put(&dev->kref, skel_delete); return retval; } @@ -354,20 +369,21 @@ static void skel_disconnect(struct usb_interface *interface) int minor = interface->minor; /* prevent skel_open() from racing skel_disconnect() */ - lock_kernel(); + mutex_lock(&skel_open_lock); dev = usb_get_intfdata(interface); usb_set_intfdata(interface, NULL); /* give back our minor */ usb_deregister_dev(interface, &skel_class); + mutex_unlock(&skel_open_lock); /* prevent more I/O from starting */ mutex_lock(&dev->io_mutex); dev->interface = NULL; mutex_unlock(&dev->io_mutex); - unlock_kernel(); + /* decrement our usage count */ kref_put(&dev->kref, skel_delete); @@ -380,6 +396,7 @@ static struct usb_driver skel_driver = { .probe = skel_probe, .disconnect = skel_disconnect, .id_table = skel_table, + .supports_autosuspend = 1, }; static int __init usb_skel_init(void) |