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

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Date:	Thu, 1 Jan 2009 12:45:36 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Alexander E. Patrakov" <patrakov@...il.com>
cc:	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Enable CONFIG_USB_SUSPEND by default or some mobile HD can't be
   unplugged safely

On Thu, 1 Jan 2009, Alexander E. Patrakov wrote:

> Yan Li wrote:
> > Hello List,
> > 
> > By default CONFIG_USB_SUSPEND is not enabled and today I got bite by
> > this when I got a new WDC My Book hard drive. I have no way to unplug
> > it safely, according to it's manual, with a kernel that doesn't have
> > CONFIG_USB_SUSPEND=y.
> > 
> > On it's manual read "you should unplug and remove the device only when
> > the light is off." On Linux unmounting it won't turn it's light off
> > and I can feel it's motor is still running.  The only way to unplug it
> > properly on a Linux system, as to my knowledge, is to echo `suspend'
> > to `/sys/bus/usb/devices/$DEV/power/level'. And one has to have
> > CONFIG_USB_SUSPEND=y to do this.
> > 
> > On Windows and Mac OS, `safely remove this device' function effectly
> > turns it into `suspend' mode, and it's light off.
> 
> You have obviously tested only Windows XP, because Vista doesn't cut the 
> power for at least some USB devices.

Yan never said that Windows cuts any power; he only said that the light 
turns off.  This is accomplished by disabling the USB port, not by 
cutting power.

> And congratulations for obtaining a 
> Vista-incompatible hard drive (of course, joking).
> 
> BTW, does the "eject /dev/$DEV" command help?

I wouldn't expect it to help, since it doesn't disable the port or put 
the device into suspend mode.

Alan Stern

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