Messages in this thread | | | Date | Wed, 27 Jul 2022 15:03:49 +0200 | Subject | Re: [PATCH 4/4] dt-bindings: firmware: Add Qualcomm UEFI Secure Application client | From | Maximilian Luz <> |
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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
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