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From: Alan Stern <stern@rowland.harvard.edu>
To: "Lu, Baolu" <baolu.lu@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Mathias Nyman <mathias.nyman@intel.com>,
	<linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] usb: notify hcd when USB device suspend or resume
Date: Thu, 7 May 2015 10:34:20 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1505071031200.2272-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <554AB169.4060100@linux.intel.com>

On Thu, 7 May 2015, Lu, Baolu wrote:

> >> +	void	(*device_suspend)(struct usb_hcd *, struct usb_device *udev,
> >> +			pm_message_t msg);
> >> +	void	(*device_resume)(struct usb_hcd *, struct usb_device *udev,
> >> +			pm_message_t msg);
> >>   };
> > Your callbacks don't use the msg argument.  What makes you think it is
> > needed?
> 
> This msg argument is valuable. XHCI spec defines a capability named FSC
> (Force Save context Capability). When this capability is implemented, the
> Save State operation (do during host suspend) shall save any cached Slot,
> Endpoint, Stream or other Context information to memory. xHCI hcd could
> use this "msg" to determine whether it needs to issue stop endpoint with
> SP (suspend) bit set.

I don't understand.  What is the advantage of using FSC?

How would xhci-hcd use "msg" to determine this?  And why doesn't your
2/3 patch already do it?

Alan Stern


  reply	other threads:[~2015-05-07 14:34 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-06  7:39 [PATCH v2 0/3] usb: notify hcd when USB device suspend or resume Lu Baolu
2015-05-06  7:40 ` [PATCH v2 1/3] " Lu Baolu
2015-05-06 14:35   ` Alan Stern
2015-05-07  0:27     ` Lu, Baolu
2015-05-07 14:34       ` Alan Stern [this message]
2015-05-08  1:14         ` Lu, Baolu
2015-05-08 14:21           ` Alan Stern
2015-05-09  0:42             ` Lu, Baolu
2015-05-11 14:25               ` Alan Stern
2015-05-12  2:05                 ` Lu, Baolu
2015-05-12 15:54                   ` Alan Stern
2015-05-13  2:36                     ` Lu, Baolu
2015-05-13 14:14                       ` Alan Stern
2015-05-08  7:55     ` Lu, Baolu
2015-05-06  7:40 ` [PATCH v2 2/3] usb: xhci: implement device_suspend/device_resume entries Lu Baolu
2015-05-06 14:30   ` Alan Stern
2015-05-07  0:30     ` Lu, Baolu
2015-05-06  7:40 ` [PATCH v2 3/3] usb: xhci: remove stop device and ring doorbell in hub control and bus suspend Lu Baolu

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