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There are a few (new) usbdevfs capabilities which an application cannot discover in any other way then checking the kernel version. There are 3 problems with this: 1) It is just not very pretty. 2) Given the tendency of enterprise distros to backport stuff it is not reliable. 3) As discussed in length on the mailinglist, USBDEVFS_URB_BULK_CONTINUATION does not work as it should when combined with USBDEVFS_URB_SHORT_NOT_OK (which is its intended use) on devices attached to an XHCI controller. So the availability of these features can be host controller dependent, making depending on them based on the kernel version not a good idea. This patch besides adding the new ioctl also adds flags for the following existing capabilities: USBDEVFS_CAP_ZERO_PACKET, available since 2.6.31 USBDEVFS_CAP_BULK_CONTINUATION, available since 2.6.32, except for XHCI USBDEVFS_CAP_NO_PACKET_SIZE_LIM, available since 3.3 Note that this patch only does not advertise the USBDEVFS_URB_BULK_CONTINUATION cap for XHCI controllers, bulk transfers with this flag set will still be accepted when submitted to XHCI controllers. Returning -EINVAL for them would break existing apps, and in most cases the troublesome scenario wrt USBDEVFS_URB_SHORT_NOT_OK urbs on XHCI controllers will never get hit, so this would break working use cases. The disadvantage of not returning -EINVAL is that cases were it is causing real trouble may go undetected / the cause of the trouble may be unclear, but this is the best we can do. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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atm | ||
c67x00 | ||
chipidea | ||
class | ||
core | ||
dwc3 | ||
early | ||
gadget | ||
host | ||
image | ||
misc | ||
mon | ||
musb | ||
otg | ||
phy | ||
renesas_usbhs | ||
serial | ||
storage | ||
wusbcore | ||
Kconfig | ||
Makefile | ||
README | ||
usb-common.c | ||
usb-skeleton.c |
To understand all the Linux-USB framework, you'll use these resources: * This source code. This is necessarily an evolving work, and includes kerneldoc that should help you get a current overview. ("make pdfdocs", and then look at "usb.pdf" for host side and "gadget.pdf" for peripheral side.) Also, Documentation/usb has more information. * The USB 2.0 specification (from www.usb.org), with supplements such as those for USB OTG and the various device classes. The USB specification has a good overview chapter, and USB peripherals conform to the widely known "Chapter 9". * Chip specifications for USB controllers. Examples include host controllers (on PCs, servers, and more); peripheral controllers (in devices with Linux firmware, like printers or cell phones); and hard-wired peripherals like Ethernet adapters. * Specifications for other protocols implemented by USB peripheral functions. Some are vendor-specific; others are vendor-neutral but just standardized outside of the www.usb.org team. Here is a list of what each subdirectory here is, and what is contained in them. core/ - This is for the core USB host code, including the usbfs files and the hub class driver ("khubd"). host/ - This is for USB host controller drivers. This includes UHCI, OHCI, EHCI, and others that might be used with more specialized "embedded" systems. gadget/ - This is for USB peripheral controller drivers and the various gadget drivers which talk to them. Individual USB driver directories. A new driver should be added to the first subdirectory in the list below that it fits into. image/ - This is for still image drivers, like scanners or digital cameras. ../input/ - This is for any driver that uses the input subsystem, like keyboard, mice, touchscreens, tablets, etc. ../media/ - This is for multimedia drivers, like video cameras, radios, and any other drivers that talk to the v4l subsystem. ../net/ - This is for network drivers. serial/ - This is for USB to serial drivers. storage/ - This is for USB mass-storage drivers. class/ - This is for all USB device drivers that do not fit into any of the above categories, and work for a range of USB Class specified devices. misc/ - This is for all USB device drivers that do not fit into any of the above categories.