Re: [PATCH v2] virtio-gpu: add VIRTIO_GPU_F_EDID feature

From: Daniel Vetter <daniel@ffwll.ch>
To: Christophe de Dinechin <cdupontd@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>,
	kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
	David Airlie <airlied@linux.ie>,
	open list <linux-kernel@vger.kernel.org>,
	Jason Wang <jasowang@redhat.com>,
	virtio-dev@redhat.com, dri-devel@lists.freedesktop.org,
	"open list:VIRTIO GPU DRIVER"
	<virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH v2] virtio-gpu: add VIRTIO_GPU_F_EDID feature
Date: Fri, 5 Oct 2018 16:41:27 +0200	[thread overview]
Message-ID: <20181005144127.GE31561@phenom.ffwll.local> (raw)
In-Reply-To: <1BA83F18-87E5-4B01-A2D9-01777078B637@redhat.com>

On Fri, Oct 05, 2018 at 04:38:11PM +0200, Christophe de Dinechin wrote:
> 
> 
> > On 5 Oct 2018, at 14:51, Gerd Hoffmann <kraxel@redhat.com> wrote:
> > 
> > The feature allows the guest request an EDID blob (describing monitor
> > capabilities) for a given scanout (aka virtual monitor connector).
> > 
> > It brings a new command message, which has just a scanout field (beside
> > the standard virtio-gpu header) and a response message which carries the
> > EDID data.
> > 
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> > ---
> > include/uapi/linux/virtio_gpu.h | 17 +++++++++++++++++
> > 1 file changed, 17 insertions(+)
> > 
> > diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
> > index f43c3c6171..1cef1ff339 100644
> > --- a/include/uapi/linux/virtio_gpu.h
> > +++ b/include/uapi/linux/virtio_gpu.h
> > @@ -41,6 +41,7 @@
> > #include <linux/types.h>
> > 
> > #define VIRTIO_GPU_F_VIRGL 0
> > +#define VIRTIO_GPU_F_EDID  1
> > 
> > enum virtio_gpu_ctrl_type {
> > 	VIRTIO_GPU_UNDEFINED = 0,
> > @@ -56,6 +57,7 @@ enum virtio_gpu_ctrl_type {
> > 	VIRTIO_GPU_CMD_RESOURCE_DETACH_BACKING,
> > 	VIRTIO_GPU_CMD_GET_CAPSET_INFO,
> > 	VIRTIO_GPU_CMD_GET_CAPSET,
> > +	VIRTIO_GPU_CMD_GET_EDID,
> > 
> > 	/* 3d commands */
> > 	VIRTIO_GPU_CMD_CTX_CREATE = 0x0200,
> > @@ -76,6 +78,7 @@ enum virtio_gpu_ctrl_type {
> > 	VIRTIO_GPU_RESP_OK_DISPLAY_INFO,
> > 	VIRTIO_GPU_RESP_OK_CAPSET_INFO,
> > 	VIRTIO_GPU_RESP_OK_CAPSET,
> > +	VIRTIO_GPU_RESP_OK_EDID,
> > 
> > 	/* error responses */
> > 	VIRTIO_GPU_RESP_ERR_UNSPEC = 0x1200,
> > @@ -291,6 +294,20 @@ struct virtio_gpu_resp_capset {
> > 	__u8 capset_data[];
> > };
> > 
> > +/* VIRTIO_GPU_CMD_GET_EDID */
> > +struct virtio_gpu_get_edid {
> > +	struct virtio_gpu_ctrl_hdr hdr;
> > +	__le32 scanout;
> > +};
> > +
> > +/* VIRTIO_GPU_RESP_OK_EDID */
> > +struct virtio_gpu_resp_edid {
> > +	struct virtio_gpu_ctrl_hdr hdr;
> > +	__le32 scanout;
> > +	__le32 size;
> > +	__u8 edid[1024];
> 
> Wouldn’t it be enough to stick to EDID 2.0 (256 bytes)?
> 
> If not, maybe add comment to explain why you chose 1024.

EDID in the wild can be up to 512 bytes.
-Daniel

> 
> > +};
> > +
> > #define VIRTIO_GPU_EVENT_DISPLAY (1 << 0)
> > 
> > struct virtio_gpu_config {
> > -- 
> > 2.9.3
> > 
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch