From: Sam Bishop <[EMAIL PROTECTED]>
This patch adds a limit on the number of URBs in flight, per device, and
the size of temporary write buffers.
---
This is similar to the approach I used to add double buffering to the
2.4 version of usb-skeleton.c.
--- linux-2.6.14.4/drivers/usb/usb-skeleton.c.orig 2005-12-14
16:50:41.000000000 -0700
+++ linux-2.6.14.4/drivers/usb/usb-skeleton.c 2005-12-16
20:27:37.656219376 -0700
@@ -1,5 +1,5 @@
/*
- * USB Skeleton driver - 2.0
+ * USB Skeleton driver - 2.1
*
* Copyright (C) 2001-2004 Greg Kroah-Hartman ([EMAIL PROTECTED])
*
@@ -8,8 +8,7 @@
* published by the Free Software Foundation, version 2.
*
* This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
- * but has been rewritten to be easy to read and use, as no locks are now
- * needed anymore.
+ * but has been rewritten to be easier to read and use.
*
*/
@@ -39,6 +38,10 @@ MODULE_DEVICE_TABLE (usb, skel_table);
/* Get a minor range for your devices from the usb maintainer */
#define USB_SKEL_MINOR_BASE 192
+/* You may want to modify these to best match your device */
+#define MAX_WRITE_URBS 4
+#define MAX_WRITE_BYTES (4 * 1024) /*
number of bytes per write urb */
+
/* Structure to hold all of our device specific stuff */
struct usb_skel {
struct usb_device * udev; /* the usb
device for this device */
@@ -48,6 +51,7 @@ struct usb_skel {
__u8 bulk_in_endpointAddr; /* the address
of the bulk in endpoint */
__u8 bulk_out_endpointAddr; /* the address
of the bulk out endpoint */
struct kref kref;
+ struct semaphore num_write_urbs;
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
@@ -152,6 +156,7 @@ static void skel_write_bulk_callback(str
/* free up our allocated buffer */
usb_buffer_free(urb->dev, urb->transfer_buffer_length,
urb->transfer_buffer, urb->transfer_dma);
+ up(&dev->num_write_urbs);
}
static ssize_t skel_write(struct file *file, const char *user_buffer,
size_t count, loff_t *ppos)
@@ -167,6 +172,12 @@ static ssize_t skel_write(struct file *f
if (count == 0)
goto exit;
+ /* make sure that we haven't exceeded our self-imposed urb quota */
+ if (down_interruptible(&dev->num_write_urbs)) {
+ retval = -ERESTARTSYS;
+ goto exit;
+ }
+
/* create a urb, and a buffer for it, and copy the data to the
urb */
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
@@ -174,6 +185,7 @@ static ssize_t skel_write(struct file *f
goto error;
}
+ count = min(count, (size_t)MAX_WRITE_BYTES);
buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL,
&urb->transfer_dma);
if (!buf) {
retval = -ENOMEM;
@@ -207,6 +219,7 @@ exit:
error:
usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);
usb_free_urb(urb);
+ up(&dev->num_write_urbs);
return retval;
}
@@ -246,6 +259,7 @@ static int skel_probe(struct usb_interfa
}
memset(dev, 0x00, sizeof(*dev));
kref_init(&dev->kref);
+ sema_init(&dev->num_write_urbs, MAX_WRITE_URBS);
dev->udev = usb_get_dev(interface_to_usbdev(interface));
dev->interface = interface;
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