Re: [PATCH v2 11/13] media: iris: Select DMA_CONTEXT_BUS to create firmware device

Dmitry Baryshkov
2026-04-26T12:16:07Z

On Thu, Apr 23, 2026 at 03:38:25PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Apr 23, 2026 at 06:59:40PM +0530, Vishnu Reddy wrote:
> > Iris need a firmware device to enable secure PAS (peripheral
> > authentication service) support in case of non-Gunyah.
>
> As gunyah isn't ever going upstream, why is this an issue here for us at
> all?

Vishnu, this is a nice example of why we are always asking for the
complete commit message, describing the problem that you are solving.
You gave zero context for people outside of your group who don't have
a knowledge of your issue.

Please start thinking from the reviewers point of view. Or consider
yourself being an engineer in 5 years wishing to change that code and
trying to understand, would you break something if you do this or that.
You need to explain, explain and explain things.

For example (please correct it, it is based on my incomplete
understanding):

If Linux is run under the Gunyah control, the hypervisor will set up the
SMMU SID for loading the firware (and protect it from being touched by
te OS). If Linux is running in EL2 without Gunyah in play, it needs to
take care of that setup. Since loading the firmware requires separate
address mapping, corresponding SID is describing in DT as one of the
functions inside the iommu-map property. Create the child device that
will be used for allocating DMA buffers for the firmware and mapping
them to the correct SID.

Please review all your commit messages from this position and adjust /
rewrite them as necessary.

--
With best wishes
Dmitry