linux-kernel - Re: Enable CONFIG_USB_SUSPEND by default or some mobile HD can't be unplugged safely

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Date:	Sat, 3 Jan 2009 10:33:08 +0800
From:	Yan Li <elliot.li.tech@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Enable CONFIG_USB_SUSPEND by default or some mobile HD can't
	be unplugged safely

On Fri, Jan 02, 2009 at 11:04:40AM -0500, Alan Stern wrote:
> > Now I know 3 methods supposed can be used to shut the device:
> > 1. (Alan Stern said Windows use this) cut the USB port's power
> 
> I said no such thing!  In fact, I said exactly the opposite: Windows 
> does _not_ cut the port's power.  Instead it disables the port.

Sorry, my mistake.

> The best approach is to send a SYNCHRONIZE CACHE command followed by 
> START-STOP (if the device supports it), and then to disable or suspend 
> the port.  In Linux, those two commands will be sent automatically if 
> you unbind the device from usb-storage.  The suspend has to be done 
> manually unless you have set up a udev rule (or something equivalent) 
> to enable autosuspend for the device.  Of course, this requires 
> CONFIG_USB_SUSPEND.

Quite clear, thanks. 

-- 
Li, Yan
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