mirror of https://gitee.com/openkylin/linux.git
a4a47bc03f
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> |
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atm | ||
c67x00 | ||
class | ||
core | ||
early | ||
gadget | ||
host | ||
image | ||
misc | ||
mon | ||
musb | ||
otg | ||
serial | ||
storage | ||
wusbcore | ||
Kconfig | ||
Makefile | ||
README | ||
usb-skeleton.c |
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.