linux-kernel - Re: [PATCH] USB :core :Prevent USB devices to autosuspend while setting interface

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Date:   Fri, 10 Nov 2017 11:30:13 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Abhijeet@...r.kernel.org, <Kumar@...r.kernel.org>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jaejoong Kim <climbbb.kim@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Abhijeet Kumar <abhijeet.kumar@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] USB :core :Prevent USB devices to autosuspend while
 setting interface

On Fri, 10 Nov 2017 Abhijeet@...r.kernel.org wrote:

> From: Abhijeet Kumar <abhijeet.kumar@...el.com>
> 
> Runtime resume USB device in order to ensure that PM framework knows
> that the we might be using the device in a short time and doesn't
> autosuspend the device while we update it's interface. Without this
> change, if device autosuspends and the kernel polling for block
> devices is disabled through sysfs at runtime or through bootargs, then
> storage devices might never unmount since the disconnect IRQ wont be
> kicked at all.
> 
> Signed-off-by: Abhijeet Kumar <abhijeet.kumar@...el.com>

I don't see any reason for doing this.  The places that call this 
subroutine will already have made sure that the device is active.  
There's no need for an additional runtime_get.

As for disconnect IRQs, they occur whether the device is suspended or 
not (they are generated by the host controller, not by the device).

Alan Stern