linux-kernel - Re: [PATCH] Explicitly disable BT radio using rfkill interface on suspend

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Message-ID: <Pine.LNX.4.44L0.0905192212560.7309-100000@netrider.rowland.org>
Date:	Tue, 19 May 2009 22:17:59 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Mario Limonciello <mario_limonciello@...l.com>,
	<linux-usb@...r.kernel.org>, Matthew Garrett <mjg59@...f.ucam.org>,
	Marcel Holtmann <marcel@...tmann.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Explicitly disable BT radio using rfkill interface on
 suspend

On Wed, 20 May 2009, Oliver Neukum wrote:

> Am Dienstag, 19. Mai 2009 23:47:02 schrieb Mario Limonciello:
> > Hi Oliver:
> 
> > Attached are both the lsusb listings.  As you can see, the missing
> > device post-suspend is that Bluetooth radio device (which is why I
> > proposed this patch in the first place).
> 
> This explains the error in your log.
> 
> > There is a udev removal event for this device, but as I said, there are
> > no add/remove/change events for the keyboard or mouse devices.  I'm
> > attaching udevadm monitor ran from right before the suspend to right after.
> 
> That is correct the devices have been successfully resumed and thus are
> present. Generally the idea of suspened/resume is to have the same system
> after resumption. It is correct to not generate events. Usbcore cannot know
> that you use udev to switch the device from pure HID to HID + bluetooth.
> 
> > Sending the appropriate hid report to the mouse device will re-attach
> > this Bluetooth radio device to the bus.
> 
> Yes, the question is whether it is the clean thing to do.
> 
> Marcel, are the HID devices usable after hid2hci has run? Should we
> choose to not resume from power loss any hid device which hid2hci
> operated on?

I'd like to know why the device switches back from HID+bluetooth to
pure HID during a suspend-resume sequence.  Does it undergo a
reset-resume?

Here's another question: Since there is a udev removal event for the 
radio device, why not add a udev rule to switch back to HID+bluetooth 
mode every time that event occurs?

Alan Stern

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