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In the upcoming USB port power off patches, we need to know whether a USB port can ever see a disconnect event. Often USB ports are internal to a system, and users can't disconnect USB devices from that port. Sometimes those ports will remain empty, because the OEM chose not to connect an internal USB device to that port. According to ACPI Spec 9.13, PLD indicates whether USB port is user visible and _UPC indicates whether a USB device can be connected to the USB port (we'll call this "connectible"). Here's a matrix of the possible combinations: Visible Connectible Name Example ------------------------------------------------------------------------- Yes No Unknown (Invalid state.) Yes Yes Hot-plug USB ports on the outside of a laptop. A user could freely connect and disconnect USB devices. No Yes Hard-wired A USB modem hard-wired to a port on the inside of a laptop. No No Not used The port is internal to the system and will remain empty. Represent each of these four states with an enum usb_port_connect_type. The four states are USB_PORT_CONNECT_TYPE_UNKNOWN, USB_PORT_CONNECT_TYPE_HOT_PLUG, USB_PORT_CONNECT_TYPE_HARD_WIRED, and USB_PORT_NOT_USED. When we get the USB port's acpi_handle, store the state in connect_type in struct usb_port. Signed-off-by: Lan Tianyu <tianyu.lan@intel.com> Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.