linux-kernel - Re: [PATCH 2/4] soc: qcom: aoss: Add debugfs interface for sending messages

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Message-ID: <98179d9e-0c03-4659-9dcc-73a411bfa00e@lunn.ch>
Date:   Tue, 1 Aug 2023 10:45:00 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Chris Lew <quic_clew@...cinc.com>,
        Alex Elder <elder@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH 2/4] soc: qcom: aoss: Add debugfs interface for sending
 messages

On Mon, Jul 31, 2023 at 08:39:38AM -0700, Bjorn Andersson wrote:
> On Mon, Jul 31, 2023 at 10:21:31AM +0200, Andrew Lunn wrote:
> > On Sun, Jul 30, 2023 at 09:10:11PM -0700, Bjorn Andersson wrote:
> > > From: Chris Lew <clew@...eaurora.org>
> > > 
> > > In addition to the normal runtime commands, the Always On Processor
> > > (AOP) provides a number of debug commands which can be used during
> > > system debugging for things such as preventing power collapse or placing
> > > floor votes for certain resources. Some of these are documented in the
> > > Robotics RB5 "Debug AOP ADB" linked below.
> > > 
> > > Provide a debugfs interface for the developer/tester to send these
> > > commands to the AOP.
> > 
> > This sort of sending arbitrary binary blob commands is not liked,
> > since it allow user space closed source drivers. At minimum, please
> > provide a file per command, with the kernel marshalling parameters
> > into the binary format, and decoding any returned values.
> > 
> 
> Thanks for your input Andrew, that is a valid concern.
> 
> The interface is in debugfs and as such wouldn't be suitable for closed
> source drivers, as in the majority of our shipping software debugfs
> isn't enabled.

There only appears to be 3 commands, so it is now too much of a burden
to do it properly, and not have a binary blob API.

And most distros do have debugfs at least built and available, but
maybe not mounted.

      Andrew