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Date: Fri, 9 Jun 2017 10:48:41 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
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To: Yueyao Zhu <yueyao.zhu@gmail.com>
cc: Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        <linux-kernel@vger.kernel.org>, Andrew Chant <achant@google.com>,
        Badhri Jagan Sridharan <badhri@google.com>,
        Dmitry Torokhov <dtor@google.com>, Yueyao Zhu <yueyao@google.com>
Subject: Re: [PATCH 0/3] USB: add API for interface driver to vote for
 autosuspend
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On Thu, 8 Jun 2017, Yueyao Zhu wrote:

> From: Yueyao Zhu <yueyao@google.com>
> 
> Currently, if a USB driver would like to enable autosuspend on the USB
> device, usb_enable_autosuspend() seems to be the only option. However,
> this acts on the device level, and other interfaces might not desire
> to autosuspend the USB device.
> 
> For example, for the usb digital audio driver to enable autosuspend on
> a device, calling usb_enable_autosuspend() from the interface driver
> might not be a good idea as the USB device might have a keyboard HID
> interface which generally doesn't handle autosupend very well.
> 
> This patch series introduces an API for interface driver to vote
> for autosuspend on the interface, and when all interfaces agree to
> it, autosuspend can then be enabled on the usb device.

The whole idea of this seems questionable.  USB interface drivers are
generally not supposed to enable or disable autosuspend -- that is a
policy decision left up to userspace.  There are a few exceptions for 
things like hubs, but this is generally true.

Why should the USB digital audio driver want to enable autosuspend?

Alan Stern