[PATCH 4/6] accel/ivpu: Add param ioctl to identify capabilities

[Jeffrey Hugo]

On 7/31/2023 10:12 AM, Stanislaw Gruszka wrote:
> Add DRM_IVPU_PARAM_CAPABILITIES ioctl to query driver capabilities.
> For now use it for identify metric streamer and new dma memory range
> features. Currently upstream version of intel_vpu does not have those,
> they will be added it the future.

Hmm.  So I happened to remember this from Oded in the reviews for the 
first iVPU series -

"btw, I talked to Daniel about this and he told me this
major/minor/patchlevel is legacy in drm and should be deprecated, so
I'm going to send a patch to document that it is deprecated and how to
use getcap ioctl to find out the features the driver support."

So, I went to look at DRM_IOCTL_GET_CAP and it feels like something you 
should be using as it fits the purpose I see in this patch, but also I 
don't see how given that it doesn't hook to the driver.

I suspect at some point, QAIC would have its own need for a "getcap" 
API.  Feels like something we should have a common entry in uAPI for 
(ACCEL_IOCTL_GET_CAP ? ), but I don't yet see that we'll have a lot a 
commonality of the capabilities across Accel drivers.  I don't think the 
DRM method of globally defined caps is useful for Accel.

Does it make sense to have a framework level ioctl, but something that 
calls into the drivers and would allow the drivers to advertise custom 
capabilities?

Seems like we might want to decide this now, because if we define a iVPU 
specific ioctl as proposed here, but then switch to an Accel-wide 
mechanism later, iVPU is going to be stuck supporting both.

What do you think?

Oded, am I misunderstanding your earlier comment?

-Jeff