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Grant Grundler
4550718f6c
extract() and implement() have brain damaged attempts to handle 32-bit wide "fields". The problem is the index math in the original code didn't clear all the relevant bits. (offset >> 5) only compensated for 32-bit index. We need (offset >> 6) if we want to use 64-bit loads. But it was also wrong in that it tried to use quasi-aligned loads. Ie "report" was only incremented in multiples of 4 bytes and then the offset was masked off for values greater than 4 bytes. The right way is to pretend "report" points at a byte array. And offset is then only minor adjustment for < 8 bits of offset. "n" (field width) can then be as big as 24 (assuming 32-bit loads) since "offset" will never be bigger than 7. If someone needs either function to handle more than 24-bits, please document why - point at a specification or specific USB hid device - in comments in the code. extract/implement() are also an eyesore to read. Please banish whoever wrote it to read CodingStyle 3 times in a row to a classroom full of 1st graders armed with rubberbands. Or just flame them. Whatever. Globbing all the code together on two lines does NOT make it faster and is Just Wrong. I've tested this patch on j6000 (dual 750Mhz PA-RISC, 32-bit 2.6.12-rc5). Kyle McMartin tested on c3000 (up 400Mhz PA-RISC, same kernel). "p2-mate" (Peter De Schrijver?) tested on sb1250 (dual core Mips, broadcom "swarm" eval board). Signed-off-by: Grant Grundler <grundler@parisc-linux.org> Signed-off-by: Matthew Wilcox <matthew@wil.cx> Cc: Vojtech Pavlik <vojtech@suse.cz> Cc: Dmitry Torokhov <dtor@mail.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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.