On 2012/9/11 3:59, Greg KH wrote:
On Wed, Sep 05, 2012 at 01:44:34PM +0800, Lan Tianyu wrote:
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.
Shouldn't we export this information to userspace somehow through sysfs
for each of the ports? Or does that happen in some other patch?
Yeah. This will be done in near future patch.
thanks,
greg k-h
--
Best Regards
Tianyu Lan
linux kernel enabling team
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