Re: [PATCH 4/4] dt-bindings: firmware: Add Qualcomm UEFI Secure Application client
From: Maximilian Luz
Date: Wed Jul 27 2022 - 09:03:57 EST
On 7/27/22 13:38, Krzysztof Kozlowski wrote:
On 26/07/2022 19:01, Maximilian Luz wrote:
On 7/26/22 17:41, Sudeep Holla wrote:
On Tue, Jul 26, 2022 at 05:15:41PM +0200, Maximilian Luz wrote:
So ultimately I think it's better to add a DT entry for it.
I disagree for the reason that once you discover more apps running on the
secure side, you want to add more entries and update DT on the platform
every time you discover some new firmware entity and you wish to interact
with it from the non-secure side.
Just as you'll have to add a driver to the kernel and update whatever is
probing the TrEE interface and add those strings to that interface. If
you then start doing SoC-specific lists, I think you'd be pretty much
re-implementing a DT in the kernel driver...
But you don't have any of these names in the DT either. Your DT node
only indicates the presence of your driver, but does not hold any
additional information like these IDs.
Because the compatible implicates the ID-string which implicates the driver
interface. If the ID-string for uefisecapp would be different we'd very likely
need a different driver for that as well, meaning a new compatible too. I
thought it would be superfluous to put that in the DT.
Basically we start modelling firmware components in devicetree. :/
Is there really a good way around it? As far as I can see the
alternative (especially for the apps that need to be loaded manually) is
hard-coding everything in the driver. Which IMHO just spreads device
specific information everywhere.
Also: Let's use the TPM app as example. If that would be a SPI or I2C
device, you'd model it in the DT. Just because it's a hardware device
that's accessible via SCM/firmware you now don't?
If I were absolutely certain that there is a reliable mechanism to
detect these apps, I'd agree with having a driver to instantiate those
devices. But I am not.
Regards,
Max