USB: usb-skeleton: usb anchor to implement flush

This patch set introduces usb_anchor and uses it to implement all modern
APIs in the skeleton driver.

- proper error reporting in the skeleton driver
- implementation of flush()

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 65 insertions, 7 deletions

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 38f8e4df9dd6..a31fcfd5eda7 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -51,16 +51,20 @@ struct usb_skel {
         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 */
+        struct usb_anchor       submitted;              /* in case we need to retract our submissions */
         unsigned char           *bulk_in_buffer;        /* the buffer to receive data */
         size_t                  bulk_in_size;           /* the size of the receive buffer */
         __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
         __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
+        int                     errors;                 /* the last request tanked */
+        spinlock_t              err_lock;               /* lock for errors */
         struct kref             kref;
         struct mutex            io_mutex;               /* synchronize I/O with disconnect */
 };
 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
 
 static struct usb_driver skel_driver;
+static void skel_draw_down(struct usb_skel *dev);
 
 static void skel_delete(struct kref *kref)
 {
@@ -130,6 +134,30 @@ static int skel_release(struct inode *inode, struct file *file)
         return 0;
 }
 
+static int skel_flush(struct file *file, fl_owner_t id)
+{
+        struct usb_skel *dev;
+        int res;
+
+        dev = (struct usb_skel *)file->private_data;
+        if (dev == NULL)
+                return -ENODEV;
+
+        /* wait for io to stop */
+        mutex_lock(&dev->io_mutex);
+        skel_draw_down(dev);
+
+        /* read out errors, leave subsequent opens a clean slate */
+        spin_lock_irq(&dev->err_lock);
+        res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
+        dev->errors = 0;
+        spin_unlock_irq(&dev->err_lock);
+
+        mutex_unlock(&dev->io_mutex);
+
+        return res;
+}
+
 static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
 {
         struct usb_skel *dev;
@@ -171,12 +199,16 @@ static void skel_write_bulk_callback(struct urb *urb)
         dev = (struct usb_skel *)urb->context;
 
         /* sync/async unlink faults aren't errors */
-        if (urb->status &&
-            !(urb->status == -ENOENT ||
-              urb->status == -ECONNRESET ||
-              urb->status == -ESHUTDOWN)) {
-                err("%s - nonzero write bulk status received: %d",
-                    __FUNCTION__, urb->status);
+        if (urb->status) {
+                if(!(urb->status == -ENOENT ||
+                    urb->status == -ECONNRESET ||
+                    urb->status == -ESHUTDOWN))
+                        err("%s - nonzero write bulk status received: %d",
+                            __FUNCTION__, urb->status);
+
+                spin_lock(&dev->err_lock);
+                dev->errors = urb->status;
+                spin_unlock(&dev->err_lock);
         }
 
         /* free up our allocated buffer */
@@ -205,6 +237,17 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou
                 goto exit;
         }
 
+        spin_lock_irq(&dev->err_lock);
+        if ((retval = dev->errors) < 0) {
+                /* any error is reported once */
+                dev->errors = 0;
+                /* to preserve notifications about reset */
+                retval = (retval == -EPIPE) ? retval : -EIO;
+        }
+        spin_unlock_irq(&dev->err_lock);
+        if (retval < 0)
+                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) {
@@ -236,13 +279,14 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou
                           usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
                           buf, writesize, skel_write_bulk_callback, dev);
         urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+        usb_anchor_urb(urb, &dev->submitted);
 
         /* 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;
+                goto error_unanchor;
         }
 
         /* release our reference to this urb, the USB core will eventually free it entirely */
@@ -251,6 +295,8 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou
 
         return writesize;
 
+error_unanchor:
+        usb_unanchor_urb(urb);
 error:
         if (urb) {
                 usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
@@ -268,6 +314,7 @@ static const struct file_operations skel_fops = {
         .write =        skel_write,
         .open =         skel_open,
         .release =      skel_release,
+        .flush =        skel_flush,
 };
 
 /*
@@ -298,6 +345,8 @@ static int skel_probe(struct usb_interface *interface, const struct usb_device_i
         kref_init(&dev->kref);
         sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
         mutex_init(&dev->io_mutex);
+        spin_lock_init(&dev->err_lock);
+        init_usb_anchor(&dev->submitted);
 
         dev->udev = usb_get_dev(interface_to_usbdev(interface));
         dev->interface = interface;
@@ -377,6 +426,15 @@ static void skel_disconnect(struct usb_interface *interface)
         info("USB Skeleton #%d now disconnected", minor);
 }
 
+static void skel_draw_down(struct usb_skel *dev)
+{
+        int time;
+
+        time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
+        if (!time)
+                usb_kill_anchored_urbs(&dev->submitted);
+}
+
 static struct usb_driver skel_driver = {
         .name =         "skeleton",
         .probe =        skel_probe,