linux-kernel - Re: [PATCH v2] usb: avoid PM error messages during resume if a device was disconnected

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Date:	Wed, 3 Jun 2009 00:53:40 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Frans Pop <elendil@...net.nl>
Cc:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: avoid PM error messages during resume if a device was disconnected

On Wednesday 03 June 2009, Frans Pop wrote:
> Currently if a laptop is suspended e.g. while docked and then resumed after
> undocking it, the following errors get generated because the USB hub in the
> docking station and the devices connected to it are no longer available:
> pm_op(): usb_dev_resume+0x0/0x10 returns -19
> PM: Device 1-2 failed to resume: error -19
> pm_op(): usb_dev_resume+0x0/0x10 returns -19
> PM: Device 1-2.2 failed to resume: error -19
> pm_op(): usb_dev_resume+0x0/0x10 returns -19
> PM: Device 1-2.3 failed to resume: error -19
> 
> As the removal of USB devices while a system is suspended is a relatively
> common use case and in most cases not an error, just return success on
> -ENODEV. The user gets informed anyway as the USB subsystem generates
> regular disconnect messages for the devices shortly afterwards:
> usb 1-2: USB disconnect, address 3
> usb 1-2.2: USB disconnect, address 4
> usblp0: removed
> usb 1-2.3: USB disconnect, address 5
> 
> Signed-off-by: Frans Pop <elendil@...net.nl>
> Cc: Alan Stern <stern@...land.harvard.edu>
> Cc: Rafael J. Wysocki <rjw@...k.pl>
> ---
> 
> On Tuesday 02 June 2009, Alan Stern wrote:
> > If we change -ENODEV to 0, the change should be made in usb_resume()
> > rather than usb_external_resume_device().
> 
> Like so?
> Agreed that it's cleaner and tested that it works just as well :-)
> 
> Cheers,
> FJP
> 
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index d0a21a5..0aaf26e 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -1762,6 +1762,7 @@ int usb_suspend(struct device *dev, pm_message_t msg)
>  int usb_resume(struct device *dev, pm_message_t msg)
>  {
>  	struct usb_device	*udev;
> +	int			status;
>  
>  	udev = to_usb_device(dev);
>  
> @@ -1771,7 +1772,14 @@ int usb_resume(struct device *dev, pm_message_t msg)
>  	 */
>  	if (udev->skip_sys_resume)
>  		return 0;
> -	return usb_external_resume_device(udev, msg);
> +	status = usb_external_resume_device(udev, msg);
> +
> +	/* Avoid PM error messages for devices disconnected while suspended
> +	 * as we'll display regular disconnect messages just a bit later.
> +	 */
> +	if (status == -ENODEV)
> +		return 0;
> +	return status;

+ return status == -ENODEV ? 0 : status;

maybe?

>  }
>  
>  #endif /* CONFIG_PM */

Best,
Rafael
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