Set custom EDID

[Stefan Hertrampf]

Hello,

we are developing a custom hypervisor backend for GVT which (from the
mediators perspective) behaves like XEN.

Currently, we are working with the Linux Kernel v5.4.41 and we are
trying to pass a custom EDID to a given vGPU.

The code flow roughly looks like this:

|vgpu = intel_gvt_ops->vgpu_create();|

|port = intel_vgpu_port(vgpu, port);||
|

|edid_data = intel_vgpu_edid_block(port);|

|memcpy(edid_data, custom_edid, EDID_SIZE);|

We are wondering how the |set_edid| callback of the |intel_gvt_mpt| is
meant to be used to receive the correct port where the virtual display
is attached. In v5.4.41 it seems, the default port is PORT_B and the
mediator only calls |set_edid| on certain platforms where it is a
different port. Is this correct?

Is there any other method to receive the correct port?

It seems that in v5.4.41 the mediator misses to call |set_edid| if the
platform |IS_COFFEELAKE|, which leads to a crash because we then assume
the default PORT_B where no memory is allocated for the EDID data.

Also in some later commits [1] the behavior is changed and the
|set_edid| callback is always called passing PORT_D. Does that mean that
the virtual display is always attached at PORT_D on newer versions of GVT?

Greetings,

Stefan


[1]
https://github.com/torvalds/linux/commit/0178f4ce3c3be4d9784c88ed512816eb653a717b

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