linux-kernel - Re: [PATCH v2 1/2] dt-bindings: remoteproc: qcom: Add firmware bindings for Q6V5

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Date:   Thu, 3 Jan 2019 16:01:45 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Sibi Sankar <sibis@...eaurora.org>, david.brown@...aro.org,
        robh+dt@...nel.org, mark.rutland@....com, andy.gross@...aro.org,
        akdwived@...eaurora.org, clew@...eaurora.org,
        linux-kernel@...r.kernel.org, linux-arm-msm-owner@...r.kernel.org,
        ohad@...ery.com, linux-remoteproc@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: remoteproc: qcom: Add firmware
 bindings for Q6V5

On Thu 03 Jan 15:50 PST 2019, Brian Norris wrote:

> On Thu, Jan 03, 2019 at 03:30:14PM -0800, Brian Norris wrote:
> > On Fri, Dec 28, 2018 at 10:18:18AM +0530, Sibi Sankar wrote:
> > > +- firmware-name:
> > > +	Usage: optional
> > > +	Value type: <string>
> > > +	Definition: must list the relative firmware image path for the
> > > +		    Hexagon Core.
> > 
> > Relative to what? I still think it's a terrible idea that your driver
> > looks for files at the top-level /lib/firmware/ directory, but now
> > you're leaking this into the device tree. This should at a bare minimum
> > be namespaced to something like the qcom/ sub-directory. But ideally,
> > the driver would automatically be deriving a further sub-directory of
> > qcom/ based on the chipset or something, and then the only thing you'd
> > describe here is some kind of variant string -- something akin to
> > ath10k's qcom,ath10k-calibration-variant (see
> > Documentation/devicetree/bindings/net/wireless/qcom,ath10k.txt), which
> > doesn't require a full path-name or any hierarchy.
> 
> Oh, I see Rob actually recommended this binding in v1, and it's (sort
> of) in use by a few other drivers. Is it really expected that we put
> arbitrary pathnames in device tree? None of the binding documentation
> seems very specific to me, and their implementations *do* allow
> arbitrary text. As it stands today, this is a great recipe for name
> collision -- e.g., how the driver today suggests "modem.XYZ" names; is
> Qualcomm really the only one out there making modems? :D
> 
> So my natural instinct is to avoid this. But if that's what everybody
> wants...
> 

I share your concern about this, but I came to suggest this as the
driver cares about platforms but the firmware is (often?)
device/product-specific.

E.g. we will serve the MTP and Pixel 3 with the qcom,sdm845-adsp-pas
compatible, but they are unlikely to run the same adsp firmware. This
allows the individual dtb to specify which firmware the driver should
use.

Regards,
Bjorn