[RFC PATCH 1/2] drm/hyperv: Add DRM driver for hyperv synthetic video device

[Deepak Rawat]

On Tue, 2020-06-23 at 02:31 +0000, Dexuan Cui wrote:
> > From: linux-hyperv-owner at vger.kernel.org
> > <linux-hyperv-owner at vger.kernel.org> On Behalf Of Deepak Rawat
> > Sent: Monday, June 22, 2020 4:06 AM
> > 
> > DRM driver for hyperv synthetic video device, based on hyperv_fb
> > framebuffer driver. Also added config option "DRM_HYPERV" to
> > enabled
> > this driver.
> 
> Hi Deepak,
> I had a quick look and overall the patch as v1 looks good to me. 

Thanks Dexuan for the review.

> 
> Some quick comments:
> 1. hyperv_vmbus_probe() assumes the existence of the PCI device,
> which
> is not true in a Hyper-V Generation-2 VM.

I guess that mean for Gen-2 VM need to rely on vmbus_allocate_mmio to
get the VRAM memory? From what I understand the pci interface anyway
maps to vmbus.

> 
> 2. It looks some other functionality in the hyperv_fb driver has not
> been
> implemented in this new driver either, e.g. the handling of the
> SYNTHVID_FEATURE_CHANGE msg.

I deliberately left this and things seems to work without this, maybe I
need to do more testing. I don't really understand the use-case
of SYNTHVID_FEATURE_CHANGE. I observed this message was received just
after vmbus connect and DRM is not yet initialized so no point updating
the situation. Even otherwise situation (mode, damage, etc.) is
triggered from user-space, not sure what to update. But will definitely
clarify on this.

> 
> Thanks,
> -- Dexuan