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>
Hans de Goede