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Subject: Re: mmap device-drivers
To: =?UTF-8?Q?Manuel_St=c3=bchn?= <freebsdnewbie@freenet.de>,
 freebsd-hackers@freebsd.org
References: <20170314090905.GA94880@freebsd-t420.fritz.box>
From: Hans Petter Selasky <hps@selasky.org>
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Date: Tue, 14 Mar 2017 10:14:59 +0100
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On 03/14/17 10:09, Manuel Stühn wrote:
> Hi,
> is it possible for a device driver to keep track if there are still
> active mmap() pointers pointing to that device?
>
> Linux does have something like
>
> struct vm_operations_struct vm_ops =
> {
>                 .close = vm_close,
> };
>
> where vm_close gets called when any mmapped pointer goes out of scope and the
> driver can refcount the mappers.
>
> Is there something similar in freebsd?

Hi,

 From what I know from the past, any memory mapped to userspace via MMAP 
can never be freed.

--HPS