The new USBDEVFS_DROP_PRIVILEGES ioctl allows a process to voluntarily
relinquish the ability to issue other ioctls that may interfere with
other processes and drivers that have claimed an interface on the
device.

This commit also includes a simple utility to be able to test the
ioctl, located at Documentation/usb/usbdevfs-drop-permissions.c

Example (with qemu-kvm's input device):

    $ lsusb
    ...
    Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd

    $ usb-devices
    ...
    C:  #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
    I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=00 Prot=02 Driver=usbhid

    $ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
    OK: privileges dropped!
    Available options:
    [0] Exit now
    [1] Reset device. Should fail if device is in use
    [2] Claim 4 interfaces. Should succeed where not in use
    [3] Narrow interface permission mask
    Which option shall I run?: 1
    ERROR: USBDEVFS_RESET failed! (1 - Operation not permitted)
    Which test shall I run next?: 2
    ERROR claiming if 0 (1 - Operation not permitted)
    ERROR claiming if 1 (1 - Operation not permitted)
    ERROR claiming if 2 (1 - Operation not permitted)
    ERROR claiming if 3 (1 - Operation not permitted)
    Which test shall I run next?: 0

After unbinding usbhid:

    $ usb-devices
    ...
    I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=00 Prot=02 Driver=(none)

    $ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
    ...
    Which option shall I run?: 2
    OK: claimed if 0
    ERROR claiming if 1 (1 - Operation not permitted)
    ERROR claiming if 2 (1 - Operation not permitted)
    ERROR claiming if 3 (1 - Operation not permitted)
    Which test shall I run next?: 1
    OK: USBDEVFS_RESET succeeded
    Which test shall I run next?: 0

After unbinding usbhid and restricting the mask:

    $ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
    ...
    Which option shall I run?: 3
    Insert new mask: 0
    OK: privileges dropped!
    Which test shall I run next?: 2
    ERROR claiming if 0 (1 - Operation not permitted)
    ERROR claiming if 1 (1 - Operation not permitted)
    ERROR claiming if 2 (1 - Operation not permitted)
    ERROR claiming if 3 (1 - Operation not permitted)

Signed-off-by: Reilly Grant <reillyg@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add a new interface for userspace to preallocate memory that can be
used with usbfs. This gives two primary benefits:

 - Zerocopy; data no longer needs to be copied between the userspace
   and the kernel, but can instead be read directly by the driver from
   userspace's buffers. This works for all kinds of transfers (even if
   nonsensical for control and interrupt transfers); isochronous also
   no longer need to memset() the buffer to zero to avoid leaking kernel data.

 - Once the buffers are allocated, USB transfers can no longer fail due to
   memory fragmentation; previously, long-running programs could run into
   problems finding a large enough contiguous memory chunk, especially on
   embedded systems or at high rates.

Memory is allocated by using mmap() against the usbfs file descriptor,
and similarly deallocated by munmap(). Once memory has been allocated,
using it as pointers to a bulk or isochronous operation means you will
automatically get zerocopy behavior. Note that this also means you cannot
modify outgoing data until the transfer is complete. The same holds for
data on the same cache lines as incoming data; DMA modifying them at the
same time could lead to your changes being overwritten.

There's a new capability USBDEVFS_CAP_MMAP that userspace can query to see
if the running kernel supports this functionality, if just trying mmap() is
not acceptable.

Largely based on a patch by Markus Rechberger with some updates. The original
patch can be found at:

  http://sundtek.de/support/devio_mmap_v0.4.diff

Signed-off-by: Steinar H. Gunderson <sesse@google.com>
Signed-off-by: Markus Rechberger <mrechberger@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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@rowland.harvard.edu>
Tested-by: Chris Dickens <christopher.a.dickens@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

This allows userspace to use bulk-streams, just like in kernel drivers, see
Documentation/usb/bulk-streams.txt for details on the in kernel API. This
is exported pretty much one on one to userspace.

To use streams an app must first make a USBDEVFS_ALLOC_STREAMS ioctl,
on success this will return the number of streams available (which may be
less then requested). If there are n streams the app can then submit
usbdevfs_urb-s with their stream_id member set to 1-n to use a specific
stream. IE if USBDEVFS_ALLOC_STREAMS returns 4 then stream_id 1-4 can be
used.

When the app is done using streams it should call USBDEVFS_FREE_STREAMS

Note applications are advised to use libusb rather then using the
usbdevfs api directly. The latest version of libusb has support for streams.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

This patch makes it possible to specify a bulk stream id when submitting
an urb using the async usbfs API. It overloads the number_of_packets
usbdevfs_urb field for this. This is not pretty, but given other
constraints it is the best we can do. The reasoning leading to this goes
as follows:

1) We want to support bulk streams in the usbfs API
2) We do not want to extend the usbdevfs_urb struct with a new member, as
   that would mean defining new ioctl numbers for all async API ioctls +
   adding compat versions for the old ones (times 2 for 32 bit support)
3) 1 + 2 means we need to re-use an existing field
4) number_of_packets is only used for isoc urbs, and streams are bulk only
   so it is the best (and only) candidate for re-using

Note that:
1) This patch only uses number_of_packets as stream_id if the app has
   actually allocated streams on the ep, so that old apps which may have
   garbage in there (as it was unused until now in the bulk case), will not
   break
2) This patch does not add support for allocating / freeing bulk-streams, that
   is done in a follow up patch

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>