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

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

[Tilman Schmidt]

From: Tilman Schmidt <tilman@imap.cc>

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

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
---

--- 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

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

[Alan Stern]

On Mon, 12 Nov 2007, Tilman Schmidt wrote:

> From: Tilman Schmidt <tilman@imap.cc>
> 
> Add a paragraph to Documentation/usb/power-management.txt about the
> interaction between suspend and disconnect.
> 
> Signed-off-by: Tilman Schmidt <tilman@imap.cc>
> ---
> 
> --- 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

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

[Tilman Schmidt]

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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: tilman@imap.cc
Bonn, Germany
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