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Date:   Fri, 10 Aug 2018 12:14:32 -0700
From:   Tadeusz Struk <>
To:     James Bottomley <>,
        Jarkko Sakkinen <>
Subject: Re: [PATCH v4 2/2] tpm: add support for nonblocking operation

On 08/10/2018 12:00 PM, James Bottomley wrote:
> On Fri, 2018-08-10 at 11:56 -0700, Tadeusz Struk wrote:
>> On 08/10/2018 11:48 AM, James Bottomley wrote:
>>> On Fri, 2018-08-10 at 11:21 -0700, Tadeusz Struk wrote:
>>>> and the feedback I got from Jason was:
>>>> "I wonder if it is worth creating this when the first file is
>>>> opened.. Lots of systems have TPMs but few use the userspace.."
>>>> so I changed this to allocate the WQ on first open. I think it
>>>> makes sense, but I leave it to you to decide.
>>> If the reason is to not create a wq unless it's needed, shouldn't
>>> the condition actually be first open with flag O_NONBLOCK?
>> Not really because one can do:
>> int fd = open("/dev/tpm0", O_RDWR);
>> fcntl(fd, F_SETFL, O_NONBLOCK);
> so move the condition to first need to queue ...

That would work, even though this is not how this is usually done.
The first open looks like the sweet spot between module init
and first need to queue.

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