diff options
Diffstat (limited to 'drivers/usb/usb-skeleton.c')
| -rw-r--r-- | drivers/usb/usb-skeleton.c | 31 |
1 files changed, 20 insertions, 11 deletions
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c index 46929a1b6f2..962b28cd3a7 100644 --- a/drivers/usb/usb-skeleton.c +++ b/drivers/usb/usb-skeleton.c @@ -40,12 +40,16 @@ MODULE_DEVICE_TABLE(usb, skel_table); /* 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 */ @@ -201,12 +205,6 @@ 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 +223,14 @@ 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 +239,7 @@ 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 +248,7 @@ 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 +256,6 @@ 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 +350,7 @@ 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; } @@ -361,13 +368,14 @@ static void skel_disconnect(struct usb_interface *interface) /* give back our minor */ usb_deregister_dev(interface, &skel_class); + unlock_kernel(); /* 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 +388,7 @@ 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) |