Re: d_map_single - how should it work?

In reply to: Marcin Cieslak : "d_map_single - how should it work?"
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From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Wed, 25 Oct 2023 10:51:22 UTC

On Wed, Oct 25, 2023 at 07:58:41AM +0000, Marcin Cieslak wrote:
> Hello,
> 
> is there any documentation for cdevsw methods?
> I am interested in knowing how d_map_single should
> be written.
> 
> Most specifically, I want to know if the driver
> has a chance to track mmaped allocations on its own
> (as far as I can see there unmap(2) does not call
> any of the driver's methods).

You need d_map_single + managed cdev pager to get something like that.
You cannot get unmaps reported, only last reference drop is communicated.
See struct cdev_pager_ops for an idea what is provided.