linux-kernel - Re: [PATCH v2] usb: ehci: Only sleep for post-resume handover if devices use persist

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Message-ID: <CAODwPW-=g9fckOU7q468MoyXT=ib=hagNr2SSxY71hjBqRjCoQ@mail.gmail.com>
Date:	Thu, 25 Apr 2013 07:57:23 -0700
From:	Julius Werner <jwerner@...omium.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, Vincent Palatin <vpalatin@...omium.org>,
	Sameer Nanda <snanda@...omium.org>
Subject: Re: [PATCH v2] usb: ehci: Only sleep for post-resume handover if
 devices use persist

On Thu, Apr 25, 2013 at 7:38 AM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Wed, 24 Apr 2013, Julius Werner wrote:
>
>> The current EHCI code sleeps a flat 110ms in the resume path if there
>> was a USB 1.1 device connected to its companion controller during
>> suspend, waiting for the device to reappear and reset so that it can be
>> handed back to the companion. This is necessary if the device uses
>> persist, so that the companion controller can actually see it during its
>> own resume path.
>>
>> However, if the device doesn't use persist, this is entirely
>> unnecessary. We might just as well ignore it and have the normal device
>> detection/reset/handoff code handle it asynchronously when it eventually
>> shows up. As USB 1.1 devices are almost exclusively HIDs these days (for
>> which persist has no value), this can allow distros to shave another
>> tenth of a second off their resume time.
>
> The patch description needs to mention the new for_each_usb_device()
> core routine.
>
>> --- a/drivers/usb/host/ehci-hub.c
>> +++ b/drivers/usb/host/ehci-hub.c
>> @@ -42,6 +42,13 @@ static int ehci_hub_control(
>>       u16             wLength
>>  );
>>
>> +
>
> Unnecessary blank line added.

Sorry, will fix that.

>> +static int persist_enabled_on_companion(struct usb_device *udev, void *unused)
>> +{
>
>
>> --- a/include/linux/usb.h
>> +++ b/include/linux/usb.h
>> @@ -719,6 +719,7 @@ const struct usb_device_id *usb_match_id(struct usb_interface *interface,
>>  extern int usb_match_one_id(struct usb_interface *interface,
>>                           const struct usb_device_id *id);
>>
>> +extern int usb_for_each_dev(void *data, int (*fn)(struct usb_device *, void *));
>
> Line is too long.

The limit is 80 (inclusive), right? Without the diff's leading '+' I
count exactly that...

> Aside from these minor issues, the patch is fine.  Fix them and you can
> add
>
> Acked-by: Alan Stern <stern@...land.harvard.edu>
>
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