The usbfs API has a peculiar hole: Users are not allowed to reap their
URBs after the device has been disconnected. There doesn't seem to be
any good reason for this; it is an ad-hoc inconsistency.
The patch allows users to issue the USBDEVFS_REAPURB and
USBDEVFS_REAPURBNDELAY ioctls (together with their 32-bit counterparts
on 64-bit systems) even after the device is gone. If no URBs are
pending for a disconnected device then the ioctls will return -ENODEV
rather than -EAGAIN, because obviously no new URBs will ever be able
to complete.
The patch also adds a new capability flag for
USBDEVFS_GET_CAPABILITIES to indicate that the reap-after-disconnect
feature is supported.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Tested-by: Chris Dickens <christopher.a.dickens@xxxxxxxxx>
---
[as1773]
drivers/usb/core/devio.c | 63 ++++++++++++++++++++++----------------
include/uapi/linux/usbdevice_fs.h | 3 +
2 files changed, 39 insertions(+), 27 deletions(-)
Index: usb-3.19/include/uapi/linux/usbdevice_fs.h
===================================================================
--- usb-3.19.orig/include/uapi/linux/usbdevice_fs.h
+++ usb-3.19/include/uapi/linux/usbdevice_fs.h
@@ -128,11 +128,12 @@ struct usbdevfs_hub_portinfo {
char port [127]; /* e.g. port 3 connects to device 27 */
};
-/* Device capability flags */
+/* System and bus capability flags */
#define USBDEVFS_CAP_ZERO_PACKET 0x01
#define USBDEVFS_CAP_BULK_CONTINUATION 0x02
#define USBDEVFS_CAP_NO_PACKET_SIZE_LIM 0x04
#define USBDEVFS_CAP_BULK_SCATTER_GATHER 0x08
+#define USBDEVFS_CAP_REAP_AFTER_DISCONNECT 0x10
/* USBDEVFS_DISCONNECT_CLAIM flags & struct */
Index: usb-3.19/drivers/usb/core/devio.c
===================================================================
--- usb-3.19.orig/drivers/usb/core/devio.c
+++ usb-3.19/drivers/usb/core/devio.c
@@ -1689,7 +1689,7 @@ static struct async *reap_as(struct usb_
for (;;) {
__set_current_state(TASK_INTERRUPTIBLE);
as = async_getcompleted(ps);
- if (as)
+ if (as || !connected(ps))
break;
if (signal_pending(current))
break;
@@ -1712,7 +1712,7 @@ static int proc_reapurb(struct usb_dev_s
}
if (signal_pending(current))
return -EINTR;
- return -EIO;
+ return -ENODEV;
}
static int proc_reapurbnonblock(struct usb_dev_state *ps, void __user *arg)
@@ -1721,10 +1721,11 @@ static int proc_reapurbnonblock(struct u
struct async *as;
as = async_getcompleted(ps);
- retval = -EAGAIN;
if (as) {
retval = processcompl(as, (void __user * __user *)arg);
free_async(as);
+ } else {
+ retval = (connected(ps) ? -EAGAIN : -ENODEV);
}
return retval;
}
@@ -1854,7 +1855,7 @@ static int proc_reapurb_compat(struct us
}
if (signal_pending(current))
return -EINTR;
- return -EIO;
+ return -ENODEV;
}
static int proc_reapurbnonblock_compat(struct usb_dev_state *ps, void __user *arg)
@@ -1862,11 +1863,12 @@ static int proc_reapurbnonblock_compat(s
int retval;
struct async *as;
- retval = -EAGAIN;
as = async_getcompleted(ps);
if (as) {
retval = processcompl_compat(as, (void __user * __user *)arg);
free_async(as);
+ } else {
+ retval = (connected(ps) ? -EAGAIN : -ENODEV);
}
return retval;
}
@@ -2038,7 +2040,8 @@ static int proc_get_capabilities(struct
{
__u32 caps;
- caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM;
+ caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM |
+ USBDEVFS_CAP_REAP_AFTER_DISCONNECT;
if (!ps->dev->bus->no_stop_on_short)
caps |= USBDEVFS_CAP_BULK_CONTINUATION;
if (ps->dev->bus->sg_tablesize)
@@ -2138,6 +2141,32 @@ static long usbdev_do_ioctl(struct file
return -EPERM;
usb_lock_device(dev);
+
+ /* Reap operations are allowed even after disconnection */
+ switch (cmd) {
+ case USBDEVFS_REAPURB:
+ snoop(&dev->dev, "%s: REAPURB\n", __func__);
+ ret = proc_reapurb(ps, p);
+ goto done;
+
+ case USBDEVFS_REAPURBNDELAY:
+ snoop(&dev->dev, "%s: REAPURBNDELAY\n", __func__);
+ ret = proc_reapurbnonblock(ps, p);
+ goto done;
+
+#ifdef CONFIG_COMPAT
+ case USBDEVFS_REAPURB32:
+ snoop(&dev->dev, "%s: REAPURB32\n", __func__);
+ ret = proc_reapurb_compat(ps, p);
+ goto done;
+
+ case USBDEVFS_REAPURBNDELAY32:
+ snoop(&dev->dev, "%s: REAPURBNDELAY32\n", __func__);
+ ret = proc_reapurbnonblock_compat(ps, p);
+ goto done;
+#endif
+ }
+
if (!connected(ps)) {
usb_unlock_device(dev);
return -ENODEV;
@@ -2231,16 +2260,6 @@ static long usbdev_do_ioctl(struct file
inode->i_mtime = CURRENT_TIME;
break;
- case USBDEVFS_REAPURB32:
- snoop(&dev->dev, "%s: REAPURB32\n", __func__);
- ret = proc_reapurb_compat(ps, p);
- break;
-
- case USBDEVFS_REAPURBNDELAY32:
- snoop(&dev->dev, "%s: REAPURBNDELAY32\n", __func__);
- ret = proc_reapurbnonblock_compat(ps, p);
- break;
-
case USBDEVFS_IOCTL32:
snoop(&dev->dev, "%s: IOCTL32\n", __func__);
ret = proc_ioctl_compat(ps, ptr_to_compat(p));
@@ -2252,16 +2271,6 @@ static long usbdev_do_ioctl(struct file
ret = proc_unlinkurb(ps, p);
break;
- case USBDEVFS_REAPURB:
- snoop(&dev->dev, "%s: REAPURB\n", __func__);
- ret = proc_reapurb(ps, p);
- break;
-
- case USBDEVFS_REAPURBNDELAY:
- snoop(&dev->dev, "%s: REAPURBNDELAY\n", __func__);
- ret = proc_reapurbnonblock(ps, p);
- break;
-
case USBDEVFS_DISCSIGNAL:
snoop(&dev->dev, "%s: DISCSIGNAL\n", __func__);
ret = proc_disconnectsignal(ps, p);
@@ -2304,6 +2313,8 @@ static long usbdev_do_ioctl(struct file
ret = proc_free_streams(ps, p);
break;
}
+
+ done:
usb_unlock_device(dev);
if (ret >= 0)
inode->i_atime = CURRENT_TIME;
--
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