USB: add API for userspace drivers to "claim" ports

This patch (as1258) implements a feature that users have been asking
for: It gives programs the ability to "claim" a port on a hub, via a
new usbfs ioctl.  A device plugged into a "claimed" port will not be
touched by the kernel beyond the immediate necessities of
initialization and enumeration.

In particular, when a device is plugged into a "claimed" port, the
kernel will not select and install a configuration.  And when a config
is installed by usbfs or sysfs, the kernel will not probe any drivers
for any of the interfaces.  (However the kernel will fetch various
string descriptors during enumeration.  One could argue that this
isn't really necessary, but the strings are exported in sysfs.)

The patch does not guarantee exclusive access to these devices; it is
still possible for more than one program to open the device file
concurrently.  Programs are responsible for coordinating access among
themselves.

A demonstration program showing how to use the new interface can be 
found in an attachment to

	http://marc.info/?l=linux-usb&m=124345857431452&w=2

The patch also makes a small simplification to the hub driver,
replacing a bunch of more-or-less useless variants of "out of memory"
with a single message.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 4247eccf858..165de5d5900 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -52,6 +52,7 @@
 
 #include "hcd.h"	/* for usbcore internals */
 #include "usb.h"
+#include "hub.h"
 
 #define USB_MAXBUS			64
 #define USB_DEVICE_MAX			USB_MAXBUS * 128
@@ -655,6 +656,7 @@ static int usbdev_release(struct inode *inode, struct file *file)
 	struct async *as;
 
 	usb_lock_device(dev);
+	usb_hub_release_all_ports(dev, ps);
 
 	/* Protect against simultaneous open */
 	mutex_lock(&usbfs_mutex);
@@ -1548,6 +1550,29 @@ static int proc_ioctl_compat(struct dev_state *ps, compat_uptr_t arg)
 }
 #endif
 
+static int proc_claim_port(struct dev_state *ps, void __user *arg)
+{
+	unsigned portnum;
+	int rc;
+
+	if (get_user(portnum, (unsigned __user *) arg))
+		return -EFAULT;
+	rc = usb_hub_claim_port(ps->dev, portnum, ps);
+	if (rc == 0)
+		snoop(&ps->dev->dev, "port %d claimed by process %d: %s\n",
+			portnum, task_pid_nr(current), current->comm);
+	return rc;
+}
+
+static int proc_release_port(struct dev_state *ps, void __user *arg)
+{
+	unsigned portnum;
+
+	if (get_user(portnum, (unsigned __user *) arg))
+		return -EFAULT;
+	return usb_hub_release_port(ps->dev, portnum, ps);
+}
+
 /*
  * NOTE:  All requests here that have interface numbers as parameters
  * are assuming that somehow the configuration has been prevented from
@@ -1689,6 +1714,16 @@ static int usbdev_ioctl(struct inode *inode, struct file *file,
 		snoop(&dev->dev, "%s: IOCTL\n", __func__);
 		ret = proc_ioctl_default(ps, p);
 		break;
+
+	case USBDEVFS_CLAIM_PORT:
+		snoop(&dev->dev, "%s: CLAIM_PORT\n", __func__);
+		ret = proc_claim_port(ps, p);
+		break;
+
+	case USBDEVFS_RELEASE_PORT:
+		snoop(&dev->dev, "%s: RELEASE_PORT\n", __func__);
+		ret = proc_release_port(ps, p);
+		break;
 	}
 	usb_unlock_device(dev);
 	if (ret >= 0)