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

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Date:   Fri, 5 Oct 2018 17:33:50 +0200
From:   Christophe de Dinechin <cdupontd@...hat.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Gerd Hoffmann <kraxel@...hat.com>, kvm@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        Jason Wang <jasowang@...hat.com>, virtio-dev@...hat.com,
        dri-devel@...ts.freedesktop.org,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v2] virtio-gpu: add VIRTIO_GPU_F_EDID feature

> On 5 Oct 2018, at 16:41, Daniel Vetter <daniel@...ll.ch> wrote:
> 
> On Fri, Oct 05, 2018 at 04:38:11PM +0200, Christophe de Dinechin wrote:
>> 
>> 
>>> On 5 Oct 2018, at 14:51, Gerd Hoffmann <kraxel@...hat.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@...hat.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.

Does this return a physical EDID? I thought it would be made-up by virtio-gpu.

Thanks,
Christophe

> 
>> 
>>> +};
>>> +
>>> #define VIRTIO_GPU_EVENT_DISPLAY (1 << 0)
>>> 
>>> struct virtio_gpu_config {
>>> -- 
>>> 2.9.3
>>> 
>> 
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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