netdev - Re: [PATCH v1 1/7] USB: adds comment on suspend callback

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Message-ID: <Pine.LNX.4.44L0.1303061012330.1955-100000@iolanthe.rowland.org>
Date:	Wed, 6 Mar 2013 10:25:27 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ming Lei <ming.lei@...onical.com>
cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Oliver Neukum <oneukum@...e.de>,
	<netdev@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-input@...r.kernel.org>
Subject: Re: [PATCH v1 1/7] USB: adds comment on suspend callback

On Wed, 6 Mar 2013, Ming Lei wrote:

> This patch adds comments on interface driver suspend callback
> to emphasize that the failure return value is ignored by
> USB core in system sleep context, so do not try to recover
> device for this case and let resume/reset_resume callback
> handle the suspend failure if needed.

In this same patch you should also update the kerneldoc for 
usb_suspend_both().  It should mention that errors returned by the 
suspend method for @udev will be ignored during system suspend.

> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
>  include/linux/usb.h |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index 4d22d0f..6e66dc4 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -978,7 +978,14 @@ struct usbdrv_wrap {
>   *	the "usbfs" filesystem.  This lets devices provide ways to
>   *	expose information to user space regardless of where they
>   *	do (or don't) show up otherwise in the filesystem.
> - * @suspend: Called when the device is going to be suspended by the system.
> + * @suspend: Called when the device is going to be suspended by the
> + *	system either from system sleep or runtime suspend context, and
> + *	its failure return value will be ignored in system sleep context,

This is an ungrammatical run-on sentence.  s/, and its failure/. The/

> + *	so do NOT try to recover device for this case. It is suggested
> + *	the callback always return 0 if resume/reset_resume callback can
> + *	handle system sususpend failure at default, otherwise driver
> + *	need to record the suspend failure and let resume/reset_resume
> + *	handle previous system suspend failure to recover device.

I don't understand what this is supposed to mean.  How about this
instead?  "so do NOT try to continue using the device if suspend fails
in this case.  Instead, let the resume or reset-resume routine recover
from the failure."

Alan Stern

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