linux-kernel - Re: [linux-usb-devel] [PATCH 1/3] UEAGLE : be suspend friendly

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Message-ID: <Pine.LNX.4.44L0.0610051621410.7144-100000@iolanthe.rowland.org>
Date:	Thu, 5 Oct 2006 16:29:51 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	Duncan Sands <baldrick@...e.fr>, <usbatm@...ts.infradead.org>,
	<linux-usb-devel@...ts.sourceforge.net>, <greg@...ah.com>,
	<linux-kernel@...r.kernel.org>, ueagle <ueagleatm-dev@....org>,
	matthieu castet <castet.matthieu@...e.fr>
Subject: Re: [linux-usb-devel] [PATCH 1/3] UEAGLE : be suspend friendly

On Thu, 5 Oct 2006, Pavel Machek wrote:

> Hi!
> 
> > > > Plug/unplug should be easy enough to simulate from usb driver, no?
> > > 
> > > if a USB driver doesn't define suspend/resume methods, then the core simply
> > > unplugs it on suspend, and replugs on resume (IIRC).
> > 
> > No longer true, and IIRC it never was.  All that happens is that URB 
> > submissions fail with -EHOSTUNREACH once the device is suspended.
> 
> Could we get "old" behaviour for devices like this? "printk("please
> unplug/replug me\n")" is not a good solution.

I would much rather see this fixed in the driver itself.

For the time being, a "dummy" suspend routine could look like this:

static int foo_suspend(struct usb_interface *intf, pm_message_t msg)
{
	up(&intf->dev.sem);
	device_release_driver(&intf->dev);
	down(&intf->dev.sem);
	return 0;
}

Getting reprobed during resume would be more difficult; it would need help 
from userspace.

Maybe UEAGLE can do something a little more sensible...

Alan Stern

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