netdev - Re: sfc userland MCDI - request for guidance

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Date:	Sat, 16 Jan 2016 11:03:09 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Edward Cree <ecree@...arflare.com>
Cc:	netdev <netdev@...r.kernel.org>,
	linux-net-drivers <linux-net-drivers@...arflare.com>
Subject: Re: sfc userland MCDI - request for guidance

Fri, Jan 15, 2016 at 06:34:04PM CET, ecree@...arflare.com wrote:
>I have a design problem with a few possible solutions and I'd like some
> guidance on which ones would be likely to be acceptable.
>
>The sfc driver communicates with the hardware using a protocol called MCDI -
> Management Controller to Driver Interface - and for various reasons
> (ranging from test automation to configuration utilities) we would like to
> be able to do this from userspace.  We currently have two ways of handling
> this, neither of which is satisfactory.

It is wrong to send commands to HW directly to userspace. Please, do
proper in-kernel vendor neutral feature abstraction and the implement
in your driver. That is how things work. Userspace->HW bypass
is simply unacceptable.