Re: [PATCH v11 03/11] firmware: xilinx: Add zynqmp IOCTL API for device control

From: Moritz Fischer <moritz.fischer@ettus.com>
To: Olof Johansson <olof@lixom.net>
Cc: Jolly Shah <jolly.shah@xilinx.com>,
	"ard.biesheuvel@linaro.org" <ard.biesheuvel@linaro.org>,
	Ingo Molnar <mingo@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	matt@codeblueprint.co.uk, Sudeep Holla <sudeep.holla@arm.com>,
	hkallweit1@gmail.com, Kees Cook <keescook@chromium.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Michal Simek <michal.simek@xilinx.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-clk <linux-clk@vger.kernel.org>,
	rajanv@xilinx.com,
	Linux ARM Mailing List <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	DTML <devicetree@vger.kernel.org>, Jolly Shah <jollys@xilinx.com>
Subject: Re: [PATCH v11 03/11] firmware: xilinx: Add zynqmp IOCTL API for device control
Date: Sun, 9 Sep 2018 12:20:09 -0700	[thread overview]
Message-ID: <CAAtXAHfwpKagBUQSFLJ1bBsxvbvyg=+nCuQv11eD+nhuxD=1_A@mail.gmail.com> (raw)
In-Reply-To: <CAOesGMi7Q9L4oZkUubKtV-m8XD67MQ05ZFhPA_0Hwky_qVUxfg@mail.gmail.com>

Hi Olof,

On Sat, Sep 8, 2018 at 6:18 PM, Olof Johansson <olof@lixom.net> wrote:
> Hi,
>
> On Fri, Aug 3, 2018 at 10:53 AM, Jolly Shah <jolly.shah@xilinx.com> wrote:
>> From: Rajan Vaja <rajanv@xilinx.com>
>>
>> Add ZynqMP firmware IOCTL API to control and configure
>> devices like PLLs, SD, Gem, etc.
>>
>> Signed-off-by: Rajan Vaja <rajanv@xilinx.com>
>> Signed-off-by: Jolly Shah <jollys@xilinx.com>
>
> This patch worries me somewhat. It's a transparent pass-through ioctl
> driver. Is there a spec available for what the implemented IOCTLs are?
>
> Should some of them be proper drivers instead of an opaque
> pass-through like this? Could some of them have stability impact on
> the platform such that there are security concerns and the list of
> arguments should somehow be sanitized?

I tend to agree with this, good catch.

> What's the intended usecase anyway? Just a debug tool during
> development, or something that you expect heavy use of by some
> userspace middleware?

I suspect it is another attempt to make userspace clocks/plls work? Scary.

Cheers,
Moritz