On Fri, 22 May 2009, Pantelis Koukousoulas wrote:
> So, as long as the kernel has a facility to allow assigning ports to userspace,
> the rest can be arranged between the userspace processes in a cooperative
> manner (and in fact this seems to be the only sufficiently clean way from what
> I can tell).
Here's a patch that implements what we discussed. It introduces two
new ioctls for usbfs: USBDEVFS_CLAIM_PORT and USBDEVFS_RELEASE_PORT. A
program can open the usbfs device file for a hub and claim various
ports on that hub. The ports are automatically released when the hub's
device file is closed.
When a new device is plugged into a "claimed" port, usbcore will not
configure it. User programs can install whatever configuration they
want. When the configuration is changed, usbcore will prevent kernel
drivers from binding to the new interfaces. User programs can claim
whichever interfaces they want.
Even though the device is "owned" by the program holding the hub's file
open, usbcore doesn't enforce any restrictions on I/O to the device's
usbfs file. User programs will have to arrange and enforce exclusive
access among themselves somehow, if that's what they want.
The patch should apply to any reasonably recent kernel. I wrote it for
2.6.30-rc6, but none of this code has changed very much recently.
Attached is a short demonstration program you can run to test the new
facility. You give it the name of a hub's device file and a port
number; it claims the port until you press Return and then releases the
port. While the port is claimed, try plugging a USB device in. It
won't be configured and no drivers will bind to it.
(If a device was already plugged in when the port is claimed, nothing
special happens to it. The drivers are not automatically unbound --
you'll have to do that yourself if that's what you want.)
Does this all sound satisfactory?
Alan Stern
Index: usb-2.6/include/linux/usbdevice_fs.h
===================================================================
--- usb-2.6.orig/include/linux/usbdevice_fs.h
+++ usb-2.6/include/linux/usbdevice_fs.h
@@ -175,4 +175,6 @@ struct usbdevfs_ioctl32 {
#define USBDEVFS_CLEAR_HALT _IOR('U', 21, unsigned int)
#define USBDEVFS_DISCONNECT _IO('U', 22)
#define USBDEVFS_CONNECT _IO('U', 23)
+#define USBDEVFS_CLAIM_PORT _IOR('U', 24, unsigned int)
+#define USBDEVFS_RELEASE_PORT _IOR('U', 25, unsigned int)
#endif /* _LINUX_USBDEVICE_FS_H */
Index: usb-2.6/drivers/usb/core/usb.h
===================================================================
--- usb-2.6.orig/drivers/usb/core/usb.h
+++ usb-2.6/drivers/usb/core/usb.h
@@ -37,6 +37,13 @@ extern int usb_match_device(struct usb_d
extern void usb_forced_unbind_intf(struct usb_interface *intf);
extern void usb_rebind_intf(struct usb_interface *intf);
+extern int usb_hub_claim_port(struct usb_device *hdev, unsigned port,
+ void *owner);
+extern int usb_hub_release_port(struct usb_device *hdev, unsigned port,
+ void *owner);
+extern void usb_hub_release_all_ports(struct usb_device *hdev, void *owner);
+extern bool usb_device_is_owned(struct usb_device *udev);
+
extern int usb_hub_init(void);
extern void usb_hub_cleanup(void);
extern int usb_major_init(void);
Index: usb-2.6/drivers/usb/core/devio.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/devio.c
+++ usb-2.6/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
@@ -642,6 +643,7 @@ static int usbdev_release(struct inode *
struct async *as;
usb_lock_device(dev);
+ usb_hub_release_all_ports(dev, ps);
/* Protect against simultaneous open */
mutex_lock(&usbfs_mutex);
@@ -1530,6 +1532,29 @@ static int proc_ioctl_compat(struct dev_
}
#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
@@ -1671,6 +1696,16 @@ static int usbdev_ioctl(struct inode *in
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)
Index: usb-2.6/drivers/usb/core/hub.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/hub.c
+++ usb-2.6/drivers/usb/core/hub.c
@@ -78,6 +78,7 @@ struct usb_hub {
u8 indicator[USB_MAXCHILDREN];
struct delayed_work leds;
struct delayed_work init_work;
+ void **port_owners;
};
@@ -860,19 +861,17 @@ static int hub_configure(struct usb_hub
u16 wHubCharacteristics;
unsigned int pipe;
int maxp, ret;
- char *message;
+ char *message = "out of memory";
hub->buffer = usb_buffer_alloc(hdev, sizeof(*hub->buffer), GFP_KERNEL,
&hub->buffer_dma);
if (!hub->buffer) {
- message = "can't allocate hub irq buffer";
ret = -ENOMEM;
goto fail;
}
hub->status = kmalloc(sizeof(*hub->status), GFP_KERNEL);
if (!hub->status) {
- message = "can't kmalloc hub status buffer";
ret = -ENOMEM;
goto fail;
}
@@ -880,7 +879,6 @@ static int hub_configure(struct usb_hub
hub->descriptor = kmalloc(sizeof(*hub->descriptor), GFP_KERNEL);
if (!hub->descriptor) {
- message = "can't kmalloc hub descriptor";
ret = -ENOMEM;
goto fail;
}
@@ -904,6 +902,12 @@ static int hub_configure(struct usb_hub
dev_info (hub_dev, "%d port%s detected\n", hdev->maxchild,
(hdev->maxchild == 1) ? "" : "s");
+ hub->port_owners = kzalloc(hdev->maxchild * sizeof(void *), GFP_KERNEL);
+ if (!hub->port_owners) {
+ ret = -ENOMEM;
+ goto fail;
+ }
+
wHubCharacteristics = le16_to_cpu(hub->descriptor->wHubCharacteristics);
if (wHubCharacteristics & HUB_CHAR_COMPOUND) {
@@ -1082,7 +1086,6 @@ static int hub_configure(struct usb_hub
hub->urb = usb_alloc_urb(0, GFP_KERNEL);
if (!hub->urb) {
- message = "couldn't allocate interrupt urb";
ret = -ENOMEM;
goto fail;
}
@@ -1131,11 +1134,13 @@ static void hub_disconnect(struct usb_in
hub_quiesce(hub, HUB_DISCONNECT);
usb_set_intfdata (intf, NULL);
+ hub->hdev->maxchild = 0;
if (hub->hdev->speed == USB_SPEED_HIGH)
highspeed_hubs--;
usb_free_urb(hub->urb);
+ kfree(hub->port_owners);
kfree(hub->descriptor);
kfree(hub->status);
usb_buffer_free(hub->hdev, sizeof(*hub->buffer), hub->buffer,
@@ -1250,6 +1255,79 @@ hub_ioctl(struct usb_interface *intf, un
}
}
+/*
+ * Allow user programs to claim ports on a hub. When a device is attached
+ * to one of these "claimed" ports, the program will "own" the device.
+ */
+static int find_port_owner(struct usb_device *hdev, unsigned port1,
+ void ***ppowner)
+{
+ if (hdev->state == USB_STATE_NOTATTACHED)
+ return -ENODEV;
+ if (port1 == 0 || port1 > hdev->maxchild)
+ return -EINVAL;
+
+ /* This assumes that devices not managed by the hub driver
+ * will always have maxchild equal to 0.
+ */
+ *ppowner = &(hdev_to_hub(hdev)->port_owners[port1 - 1]);
+ return 0;
+}
+
+/* In the following three functions, the caller must hold hdev's lock */
+int usb_hub_claim_port(struct usb_device *hdev, unsigned port1, void *owner)
+{
+ int rc;
+ void **powner;
+
+ rc = find_port_owner(hdev, port1, &powner);
+ if (rc)
+ return rc;
+ if (*powner)
+ return -EBUSY;
+ *powner = owner;
+ return rc;
+}
+
+int usb_hub_release_port(struct usb_device *hdev, unsigned port1, void *owner)
+{
+ int rc;
+ void **powner;
+
+ rc = find_port_owner(hdev, port1, &powner);
+ if (rc)
+ return rc;
+ if (*powner != owner)
+ return -ENOENT;
+ *powner = NULL;
+ return rc;
+}
+
+void usb_hub_release_all_ports(struct usb_device *hdev, void *owner)
+{
+ int n;
+ void **powner;
+
+ n = find_port_owner(hdev, 1, &powner);
+ if (n == 0) {
+ for (; n < hdev->maxchild; (++n, ++powner)) {
+ if (*powner == owner)
+ *powner = NULL;
+ }
+ }
+}
+
+/* The caller must hold udev's lock */
+bool usb_device_is_owned(struct usb_device *udev)
+{
+ struct usb_hub *hub;
+
+ if (udev->state == USB_STATE_NOTATTACHED || !udev->parent)
+ return false;
+ hub = hdev_to_hub(udev->parent);
+ return !!hub->port_owners[udev->portnum - 1];
+}
+
static void recursively_mark_NOTATTACHED(struct usb_device *udev)
{
Index: usb-2.6/drivers/usb/core/driver.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/driver.c
+++ usb-2.6/drivers/usb/core/driver.c
@@ -217,6 +217,9 @@ static int usb_probe_interface(struct de
udev = interface_to_usbdev(intf);
intf->needs_binding = 0;
+ if (usb_device_is_owned(udev))
+ return -ENODEV;
+
if (udev->authorized == 0) {
dev_err(&intf->dev, "Device is not authorized for usage\n");
return -ENODEV;
Index: usb-2.6/drivers/usb/core/generic.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/generic.c
+++ usb-2.6/drivers/usb/core/generic.c
@@ -158,7 +158,9 @@ static int generic_probe(struct usb_devi
/* Choose and set the configuration. This registers the interfaces
* with the driver core and lets interface drivers bind to them.
*/
- if (udev->authorized == 0)
+ if (usb_device_is_owned(udev))
+ ; /* Don't configure if the device is owned */
+ else if (udev->authorized == 0)
dev_err(&udev->dev, "Device is not authorized for usage\n");
else {
c = usb_choose_configuration(udev);
/* usbown -- claim and release a port on a USB hub */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/usbdevice_fs.h>
#define USBDEVFS_CLAIM_PORT _IOR('U', 24, unsigned int)
#define USBDEVFS_RELEASE_PORT _IOR('U', 25, unsigned int)
int main(int argc, char **argv)
{
const char *filename;
unsigned port;
int fd;
int rc;
int c;
if (argc != 3) {
fprintf(stderr, "Usage: usbown hub-filename portnum\n");
return 1;
}
filename = argv[1];
port = atoi(argv[2]);
fd = open(filename, O_WRONLY);
if (fd < 0) {
perror("Error opening hub device file");
return 1;
}
printf("Claiming USB hub %s port %d\n", filename, port);
rc = ioctl(fd, USBDEVFS_CLAIM_PORT, &port);
if (rc < 0) {
perror("Error in ioctl");
return 1;
}
printf("Port-claim successful\n");
printf("Press Enter to continue...");
do {
c = getc(stdin);
} while (c != '\n' && c != EOF);
printf("Releasing USB hub %s port %d\n", filename, port);
rc = ioctl(fd, USBDEVFS_RELEASE_PORT, &port);
if (rc < 0) {
perror("Error in ioctl");
return 1;
}
printf("Port-release successful\n");
close(fd);
return 0;
}
