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

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Date:	Fri, 2 Jan 2009 22:00:23 +0800
From:	Yan Li <elliot.li.tech@...il.com>
To:	Tino Keitel <tino.keitel@....de>,
	Alan Stern <stern@...land.harvard.edu>
Cc:	gregkh@...e.de, 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 10:56:43AM +0100, Tino Keitel wrote:
> With a WD My Passport drive (2,5"), I need to use sg_start --stop --pc=3
> to stop the disk before unplugging it. Maybe this works with your
> drive, too.  This is also required by some Firewire hard disks.  Maybe
> the eject command should be extended to use this method, as it is used
> also by HAL to eject hotplug devices.

Hum...  I grepped my hal and hal-info packages but haven't found any
scripts using `sg_*'. I'm using hal package 0.5.11-6 from Debian
testing.

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
2. send STOP SCSI command to stop it
3. put it into suspend mode

For the 1st method I have no much experience with Windows so I can't
verify. But now I doubt it. Since there are many early USB devices
that still show light on after you "safely remove" it from Windows. I
guess the power is still supplied but the device is send a command to
be shutdown or suspended.

For the 2nd and 3rd methods, I don't know which one is better, hope
some experts can give advice.

Whatever, I think the suspend mode is a standard USB design and the
kernel should support it by default so we should enable
CONFIG_USB_SUSPEND.

-- 
Li, Yan
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