linux-kernel - Re: [PATCH v3 2/3] usb: xhci: implement device_suspend/device

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Message-ID: <554C69CC.4030104@linux.intel.com>
Date:	Fri, 08 May 2015 15:46:20 +0800
From:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Mathias Nyman <mathias.nyman@...el.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] usb: xhci: implement device_suspend/device_resume
 entries



On 05/08/2015 03:28 PM, Greg Kroah-Hartman wrote:
> On Fri, May 08, 2015 at 09:23:40AM +0800, Lu, Baolu wrote:
>>
>> On 05/08/2015 04:47 AM, Greg Kroah-Hartman wrote:
>>> On Thu, May 07, 2015 at 10:18:15AM +0800, Lu Baolu wrote:
>>>> This patch implements device_suspend/device_resume entries for xHC driver.
>>>> device_suspend will be called when a USB device is about to suspend. It
>>>> will issue a stop endpoint command for each endpoint in this device. The
>>>> Suspend(SP) bit in the command TRB will set which will give xHC a hint
>>>> about the suspend. device_resume will be called when a USB device is just
>>>> resumed. It will ring doorbells of all endpoint unconditionally. XHC may
>>>> use these suspend/resume hints to optimize its operation.
>>>>
>>>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>>> ---
>>>>   drivers/usb/host/xhci-hub.c |  2 +-
>>>>   drivers/usb/host/xhci.c     | 40 ++++++++++++++++++++++++++++++++++++++++
>>>>   drivers/usb/host/xhci.h     | 11 +++++++++++
>>>>   3 files changed, 52 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
>>>> index 0827d7c..a83e82e 100644
>>>> --- a/drivers/usb/host/xhci-hub.c
>>>> +++ b/drivers/usb/host/xhci-hub.c
>>>> @@ -266,7 +266,7 @@ int xhci_find_slot_id_by_port(struct usb_hcd *hcd, struct xhci_hcd *xhci,
>>>>    * to complete.
>>>>    * suspend will set to 1, if suspend bit need to set in command.
>>>>    */
>>>> -static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>>>> +int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>>>>   {
>>>>   	struct xhci_virt_device *virt_dev;
>>>>   	struct xhci_command *cmd;
>>>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>>>> index ec8ac16..6b61833 100644
>>>> --- a/drivers/usb/host/xhci.c
>>>> +++ b/drivers/usb/host/xhci.c
>>>> @@ -4680,6 +4680,40 @@ int xhci_disable_usb3_lpm_timeout(struct usb_hcd *hcd,
>>>>   		return ret;
>>>>   	return 0;
>>>>   }
>>>> +
>>>> +/*
>>>> + * xHCI compatible host controller driver expects to be notified prior to
>>>> + * selectively suspending a device. xHCI hcd could optimize the endpoint
>>>> + * cache for power saving purpose. Refer to 4.15.1.1 of xHCI 1.1.
>>>> + */
>>>> +void xhci_device_suspend(struct usb_hcd *hcd,
>>>> +			struct usb_device *udev, pm_message_t msg)
>>> You never use the 'msg' field, so please remove it from the callback.
>> 'msg' could be used in another patch to determine the pm event types:
>> auto-suspend or system suspend. I didn't bring up that patch together
>> with this patch series because 1) that's part of xhci 1.1 features, and
>> 2) it's still not tested yet.
> We don't add "features" to kernel code that is not used when it is
> added.  We can always change function calls later as we do not have a
> stable api at all.

Understand it now. I will remove 'msg' fields in v4 patch series.

>
> thanks,
>
> greg k-h

Thank you.
Baolu
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