linux-kernel - Re: [RFC PATCH 0/3] Separate BE DAI HW constraints from FE ones

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <95d0f1c1-5a89-837f-b1dc-42482a3b1250@linux.intel.com>
Date:   Wed, 24 Mar 2021 10:28:24 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Codrin.Ciubotariu@...rochip.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Cc:     lgirdwood@...il.com, broonie@...nel.org, mirq-linux@...e.qmqm.pl,
        gustavoars@...nel.org, tiwai@...e.com
Subject: Re: [RFC PATCH 0/3] Separate BE DAI HW constraints from FE ones


> I am using hw_params_fixup, but it's not enough. The first thing I do is
> to not add the BE HW constraint rules in runtime->hw_constraints,
> because this will potentially affect the FE HW params. If the FE does
> sampling rate conversion, for example, applying the sampling rate
> constrain rules from a BE codec on FE is useless. The second thing I do
> is to apply these BE HW constraint rules to the BE HW params. It's true
> that the BE HW params can be fine tuned via hw_params_fixup (topology,
> device-tree or even static parameters) and set in such a way that avoid
> the BE HW constraints, so we could ignore the constraint rules added by
> their drivers. It's not every elegant and running the BE HW constraint
> rules for the fixup BE HW params can be a sanity check. Also, I am
> thinking that if the FE does no conversion (be_hw_params_fixup missing)
> and more than one BEs are available, applying the HW constraint rules on
> the same set of BE HW params could rule out the incompatible BE DAI
> links and start the compatible ones only. I am not sure this is a real
> usecase.

Even after a second cup of coffee I was not able to follow why the 
hw_params_fixup was not enough? That paragraph is rather dense.

And to be frank I don't fully understand the problem statement above: 
"separate the FE HW constraints from the BE HW constraints". We have 
existing solutions with a DSP-based SRC adjusting FE rates to what is 
required by the BE dailink.

Maybe it would help to show examples of what you can do today and what 
you cannot, so that we are on the same wavelength on what the 
limitations are and how to remove them?