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Subject: Re: [PATCH v2] virtio-gpu: add VIRTIO_GPU_F_EDID feature
From:   Christophe de Dinechin <cdupontd@redhat.com>
In-Reply-To: <20181005125154.19824-1-kraxel@redhat.com>
Date:   Fri, 5 Oct 2018 16:38:11 +0200
Cc:     virtio-dev@redhat.com, kvm@vger.kernel.org,
        dri-devel@lists.freedesktop.org, David Airlie <airlied@linux.ie>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>
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Message-Id: <1BA83F18-87E5-4B01-A2D9-01777078B637@redhat.com>
References: <20181005125154.19824-1-kraxel@redhat.com>
To:     Gerd Hoffmann <kraxel@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
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> 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.

> +};
> +
> #define VIRTIO_GPU_EVENT_DISPLAY (1 << 0)
> 
> struct virtio_gpu_config {
> -- 
> 2.9.3
>