Am Dienstag, 22. Mai 2007 21:48 schrieb David Brownell:
> On Tuesday 22 May 2007, Alan Stern wrote:
>
> > Timeouts are specified in jiffies, so your timeout argument
> > should be long or unsigned long, not int.
>
> Timeouts are best specified in milliseconds though... that's been
> the policy inside the USB stack since someone's search-and-destroy
> mission a few years back. Most people don't handle jiffies right.
Hi,
here's the use of anchors to implement a couple of methods in the
skeleton driver, which is thus brought up to standard. This patch does:
- correctly handle disconnect with an anchor
- correctly handle suspend with an anchor
- correctly handle pre_reset with an anchor
in order to have a correct handling of pre_reset it further:
- introduces error reporting in the write path
- reports resets to user space
- implements flush() to isolate consecutive calls to open()
Regards
Oliver
---
--- a/drivers/usb/usb-skeleton.c 2007-05-22 14:50:34.000000000 +0200
+++ b/drivers/usb/usb-skeleton.c 2007-05-24 08:47:29.000000000 +0200
@@ -34,10 +34,6 @@ 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
@@ -54,16 +50,20 @@ 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)
{
@@ -83,10 +83,8 @@ static int skel_open(struct inode *inode
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;
@@ -95,25 +93,26 @@ static int skel_open(struct inode *inode
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);
+ /* to guard against an ongoing reset */
+ mutex_lock(&dev->io_mutex);
/* prevent the device from being autosuspended */
retval = usb_autopm_get_interface(interface);
if (retval) {
+ mutex_unlock(&dev->io_mutex);
kref_put(&dev->kref, skel_delete);
goto exit;
}
/* save our object in the file's private structure */
file->private_data = dev;
+ mutex_unlock(&dev->io_mutex);
exit:
return retval;
@@ -138,6 +137,30 @@ static int skel_release(struct inode *in
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;
@@ -179,14 +202,17 @@ static void skel_write_bulk_callback(str
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 */
usb_buffer_free(urb->dev, urb->transfer_buffer_length,
urb->transfer_buffer, urb->transfer_dma);
@@ -213,6 +239,17 @@ static ssize_t skel_write(struct file *f
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) {
@@ -244,13 +281,14 @@ static ssize_t skel_write(struct file *f
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 */
@@ -259,6 +297,8 @@ static ssize_t skel_write(struct file *f
return writesize;
+error_unanchor:
+ usb_unanchor_urb(urb);
error:
if (urb) {
usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
@@ -276,6 +316,7 @@ static const struct file_operations skel
.write = skel_write,
.open = skel_open,
.release = skel_release,
+ .flush = skel_flush,
};
/*
@@ -306,6 +347,8 @@ static int skel_probe(struct usb_interfa
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;
@@ -368,22 +411,18 @@ static void skel_disconnect(struct usb_i
struct usb_skel *dev;
int minor = interface->minor;
- /* prevent skel_open() from racing skel_disconnect() */
- 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);
-
+ usb_kill_anchored_urbs(&dev->submitted);
/* decrement our usage count */
kref_put(&dev->kref, skel_delete);
@@ -391,10 +430,55 @@ static void skel_disconnect(struct usb_i
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 int skel_suspend(struct usb_interface *intf, pm_message_t message)
+{
+ struct usb_skel *dev = usb_get_intfdata(intf);
+
+ if (!dev)
+ return 0;
+ skel_draw_down(dev);
+ return 0;
+}
+
+static void skel_pre_reset(struct usb_interface *intf)
+{
+ struct usb_skel *dev = usb_get_intfdata(intf);
+
+ mutex_lock(&dev->io_mutex);
+ skel_draw_down(dev);
+}
+
+static int skel_resume (struct usb_interface *intf)
+{
+ return 0;
+}
+
+static void skel_post_reset(struct usb_interface *intf)
+{
+ struct usb_skel *dev = usb_get_intfdata(intf);
+
+ /* we are sure no URBs are active - no locking needed */
+ dev->errors = -EPIPE;
+ mutex_unlock(&dev->io_mutex);
+}
+
static struct usb_driver skel_driver = {
.name = "skeleton",
.probe = skel_probe,
.disconnect = skel_disconnect,
+ .suspend = skel_suspend,
+ .resume = skel_resume,
+ .pre_reset = skel_pre_reset,
+ .post_reset = skel_post_reset,
.id_table = skel_table,
.supports_autosuspend = 1,
};
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