linux/drivers/usb
Linus Torvalds a4a47bc03f Lower USB storage settling delay to something more reasonable
The five-second delay can be rather annoying, and makes the system
appear much less responsive when you connect a USB drive.

It's also not entirely clear that it is needed - the settling delay has
at least historically been an issue on some Apple iPods, for example,
and some devices have been reported to need even more than the old 5s
delay.

But before we penalize them all, let's see how bad it really is.  Some
of the reasons for long delays seem to be actual historical kernel bugs
that should probably never have been papered over with a delay in the
first place (there's a Ubuntu bug report for 2.6.20 about a NULL pointer
dereference unless 'delay_use' is 8 or more, for example).

It also looks like some distros have already shipped with delay_use=0,
so the five second default may well be totally historical.

In other words: "Let's see if anybody screams".

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-02-26 10:03:22 -08:00
..
atm firmware_class: make request_firmware_nowait more useful 2009-12-11 11:24:52 -08:00
c67x00 usb/c67x00 endianness annotations 2008-06-04 08:06:01 -07:00
class USB: usbtmc: Use usb_clear_halt() instead of custom code. 2009-12-11 11:55:27 -08:00
core USB: usbfs: properly clean up the as structure on error paths 2010-02-16 15:11:02 -08:00
early USB: fix section mismatch in early ehci dbgp 2009-12-23 11:34:11 -08:00
gadget USB: gadget: fix EEM gadget CRC usage 2010-02-16 15:11:10 -08:00
host USB: FHCI: Fix build after kfifo rework 2010-02-16 15:11:07 -08:00
image USB: remove unneeded printks from microtek driver 2009-09-23 06:46:34 -07:00
misc USB: SIS USB2VGA DRIVER: support KAIREN's USB VGA adaptor USB20SVGA-MB-PLUS 2010-02-16 15:11:05 -08:00
mon USB: add scatter-gather support to usbmon 2009-12-11 11:55:20 -08:00
musb USB: musb: workaround Blackfin FIFO anomalies 2009-12-23 11:34:19 -08:00
otg USB: otg Kconfig: let USB_OTG_UTILS select USB_ULPI option 2010-02-16 15:11:09 -08:00
serial USB: serial: add usbid for dell wwan card to sierra.c 2010-02-16 15:11:06 -08:00
storage Lower USB storage settling delay to something more reasonable 2010-02-26 10:03:22 -08:00
wusbcore USB: wusb: correctly check size of security descriptor. 2009-12-11 11:55:26 -08:00
Kconfig USB: ehci: Allow EHCI to be built on OMAP3 2009-12-11 11:55:20 -08:00
Makefile USB: Fix double-linking of drivers/usb/otg when ULPI is selected 2009-12-23 11:34:10 -08:00
README USB: fix directory references in usb/README 2007-11-28 13:58:34 -08:00
usb-skeleton.c USB: skeleton: Correct use of ! and & 2009-12-11 11:55:14 -08:00

README

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.