linux-kernel - Re: Check if usb device is suspended

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Message-ID: <CAOAoqGuiBrg_tYhdNXd3r48YC9KQ5GNm7jrV4ttNiMjNkrCKRA@mail.gmail.com>
Date:	Fri, 21 Mar 2014 17:17:09 +0530
From:	Jagdish Gedia <jvgediya@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>, oneukum@...e.de
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Check if usb device is suspended

I want to resume the usb device on some event, so i want to check if
it is suspended. I think by above method i can check if the device is
already suspended, but may be i will miss to resume the device if it
is suspending. Is there any way through which i can check if device is
suspending?

On Thu, Mar 13, 2014 at 7:50 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Thu, 13 Mar 2014, Jagdish Gedia wrote:
>
>> Hi,
>> I want to check in my driver if usb device is suspended or not?
>
> Why do you need to check?  Your driver gets told every time the device
> suspends and every time it resumes.  Therefore it should already know
> the answer.
>
>> currently i am doing it like
>>
>> if(udev->state==USB_STATE_SUSPENDED)
>>
>> Is this the proper way? Is this enough?
>
> Aside from the fact that the device's state may change immediately
> after you make this test, as Oliver pointed out, you also should
> realize that this test might not give the correct answer if the device
> is in the middle of suspending or resuming when the test runs.
>
> Alan Stern
>
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