Re: [PATCH 0/3] USB: add API for interface driver to vote for autosuspend

From	Alan Stern <stern@rowland.harvard.edu>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/3] USB: add API for interface driver to vote for autosuspend
Date	2017-06-09 17:00 +0200
Message-ID	<tQtyh-2Qa-5@gated-at.bofh.it> (permalink)
References	<tQdDb-1g9-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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

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[PATCH 0/3] USB: add API for interface driver to vote for autosuspend Yueyao Zhu <yueyao.zhu@gmail.com> - 2017-06-09 00:00 +0200
  [PATCH 3/3] sound: usb: allow interfaces that the driver claims to autosuspend Yueyao Zhu <yueyao.zhu@gmail.com> - 2017-06-09 00:00 +0200
  [PATCH 2/3] HID: usbhid: enable autosuspend for devices whose ... Yueyao Zhu <yueyao.zhu@gmail.com> - 2017-06-09 00:10 +0200
  Re: [PATCH 0/3] USB: add API for interface driver to vote for  autosuspend Alan Stern <stern@rowland.harvard.edu> - 2017-06-09 17:00 +0200

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