linux-kernel - Re: [PATCH v3] drm/virtio: Add option to disable KMS support

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Message-ID: <44e67d88-fce6-a1c1-79a9-a937e64a32bb@collabora.com>
Date:   Mon, 27 Feb 2023 20:57:04 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     Chia-I Wu <olvaffe@...il.com>, Ryan Neph <ryanneph@...omium.org>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] drm/virtio: Add option to disable KMS support

On 2/27/23 20:38, Rob Clark wrote:
...
> +	if (IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS)) {
> +		/* get display info */
> +		virtio_cread_le(vgdev->vdev, struct virtio_gpu_config,
> +				num_scanouts, &num_scanouts);
> +		vgdev->num_scanouts = min_t(uint32_t, num_scanouts,
> +					    VIRTIO_GPU_MAX_SCANOUTS);
> +		if (!vgdev->num_scanouts) {
> +			/*
> +			 * Having an EDID but no scanouts is non-sensical,
> +			 * but it is permitted to have no scanouts and no
> +			 * EDID (in which case DRIVER_MODESET and
> +			 * DRIVER_ATOMIC are not advertised)
> +			 */
> +			if (vgdev->has_edid) {
> +				DRM_ERROR("num_scanouts is zero\n");
> +				ret = -EINVAL;
> +				goto err_scanouts;
> +			}
> +			dev->driver_features &= ~(DRIVER_MODESET | DRIVER_ATOMIC);

If it's now configurable by host, why do we need the
CONFIG_DRM_VIRTIO_GPU_KMS?

-- 
Best regards,
Dmitry