Re: [RFC PATCH] usb/acpi: Add support usb port power off mechanism for device fixed on the motherboard

Lan Tianyu
2012-05-16T06:32:25Z

On 2012年05月16日 04:00, Sarah Sharp wrote:
> On Tue, May 15, 2012 at 08:18:00AM -0700, Greg KH wrote:
>> On Tue, May 15, 2012 at 10:31:38PM +0800, Lan Tianyu wrote:
>>> Since alan suggested we should start simpler version(power
>>> down port that have no devices attached) firstly. And we
>>> also should provide general power off mechanism.
>>>
>>> I have a proposal.
>>> first: add portx_power_control sys file.
>>> echo "auto" => portx_power_control
>>> check whether there is a device. if no, send the clear
>>> USB_PORT_FEAT_POWER request. (since general way
>>> to control port power is via set or clear PORT_POWER)
>>>
>>> echo "on" => portx_power_control
>>> send the set USB_PORT_FEAT_POWER request.
>>
>> No "off"?
>
> Yeah, we probably need an "off" for those libusb and ModemManager
> developers who want to try and simulate a disconnect of a misbehaving
> device.
>
> Sarah Sharp

Ok. Let me reconfirm the meaning of these opinions.

"auto"
if port without device, turn off power directly.
if port with device, turn off power when the device is suspended.

"on" the port's power must be on.

"off" the port's power must be off.

Right?

> On Tue, May 15, 2012 at 08:18:00AM -0700, Greg KH wrote:
>> Do you have a patch showing that this works?
Currently no. I will write a RFC version and send out for discuss.

--
Best Regards
Tianyu Lan
linux kernel enabling team
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