2007-11-12 10:02:28

by Tilman Schmidt

[permalink] [raw]
Subject: [PATCH] USB: power-management.txt - disconnect clarification

From: Tilman Schmidt <[email protected]>

Add a paragraph to Documentation/usb/power-management.txt about the
interaction between suspend and disconnect.

Signed-off-by: Tilman Schmidt <[email protected]>
---

--- linux-2.6/Documentation/usb/power-management.txt 2007-10-14 00:41:08.000000000 +0200
+++ linux-2.6.24-rc2-work/Documentation/usb/power-management.txt 2007-11-12 10:27:30.000000000 +0100
@@ -278,6 +278,12 @@
(although the interfaces will be in the same altsettings as
before the suspend).

+If the device is disconnected or powered down while it is suspended,
+the disconnect method will be called instead of the resume or
+reset_resume method. This will also happen if the system is resumed
+from hibernation, as the device could have been disconnected without
+the system being able to detect it.
+
The reset_resume method is used by the USB Persist facility (see
Documentation/usb/persist.txt) and it can also be used under certain
circumstances when CONFIG_USB_PERSIST is not enabled. Currently, if a


2007-11-12 19:42:30

by Alan Stern

[permalink] [raw]
Subject: Re: [PATCH] USB: power-management.txt - disconnect clarification

On Mon, 12 Nov 2007, Tilman Schmidt wrote:

> From: Tilman Schmidt <[email protected]>
>
> Add a paragraph to Documentation/usb/power-management.txt about the
> interaction between suspend and disconnect.
>
> Signed-off-by: Tilman Schmidt <[email protected]>
> ---
>
> --- linux-2.6/Documentation/usb/power-management.txt 2007-10-14 00:41:08.000000000 +0200
> +++ linux-2.6.24-rc2-work/Documentation/usb/power-management.txt 2007-11-12 10:27:30.000000000 +0100
> @@ -278,6 +278,12 @@
> (although the interfaces will be in the same altsettings as
> before the suspend).
>
> +If the device is disconnected or powered down while it is suspended,
> +the disconnect method will be called instead of the resume or
> +reset_resume method. This will also happen if the system is resumed
> +from hibernation, as the device could have been disconnected without
> +the system being able to detect it.
> +

I don't like the second sentence very much. How about something like
this instead:

+If the device is disconnected or powered down while it is suspended,
+the disconnect method will be called instead of the resume or
+reset_resume method. This is also quite likely to happen when
+waking up from hibernation, as many systems do not maintain suspend
+current to the USB host controllers during hibernation. (It's
+possible to work around the hibernation-forces-disconnect problem by
+using the USB-Persist facility, described in
+Documentation/usb/persist.txt.)

Alan Stern

2007-11-15 21:32:43

by Tilman Schmidt

[permalink] [raw]
Subject: Re: [PATCH] USB: power-management.txt - disconnect clarification

Am 12.11.2007 20:42 schrieb Alan Stern:

> I don't like the second sentence very much. How about something like
> this instead:
>
> +If the device is disconnected or powered down while it is suspended,
> +the disconnect method will be called instead of the resume or
> +reset_resume method. This is also quite likely to happen when
> +waking up from hibernation, as many systems do not maintain suspend
> +current to the USB host controllers during hibernation. (It's
> +possible to work around the hibernation-forces-disconnect problem by
> +using the USB-Persist facility, described in
> +Documentation/usb/persist.txt.)

Fine by me.

--
Tilman Schmidt E-Mail: [email protected]
Bonn, Germany
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