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SubjectRe: [PATCH] drm/virtio: Add option to disable KMS support
From
Hi

Am 24.02.23 um 19:02 schrieb Rob Clark:
> From: Rob Clark <robdclark@chromium.org>
>
> Add a build option to disable modesetting support. This is useful in
> cases where the guest only needs to use the GPU in a headless mode, or
> (such as in the CrOS usage) window surfaces are proxied to a host
> compositor.

We've just been discussing this on IRC, but failed to see the practical
benefit. It's not like the modesetting code takes up lots of memory.
What's the real-world use case?

Best regards
Thomas

>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
> drivers/gpu/drm/virtio/Kconfig | 11 +++++++++++
> drivers/gpu/drm/virtio/Makefile | 5 ++++-
> drivers/gpu/drm/virtio/virtgpu_drv.c | 6 +++++-
> drivers/gpu/drm/virtio/virtgpu_drv.h | 10 ++++++++++
> drivers/gpu/drm/virtio/virtgpu_kms.c | 6 ++++++
> 5 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/Kconfig b/drivers/gpu/drm/virtio/Kconfig
> index 51ec7c3240c9..ea06ff2aa4b4 100644
> --- a/drivers/gpu/drm/virtio/Kconfig
> +++ b/drivers/gpu/drm/virtio/Kconfig
> @@ -11,3 +11,14 @@ config DRM_VIRTIO_GPU
> QEMU based VMMs (like KVM or Xen).
>
> If unsure say M.
> +
> +config DRM_VIRTIO_GPU_KMS
> + bool "Virtio GPU driver modesetting support"
> + depends on DRM_VIRTIO_GPU
> + default y
> + help
> + Enable modesetting support for virtio GPU driver. This can be
> + disabled in cases where only "headless" usage of the GPU is
> + required.
> +
> + If unsure, say Y.
> diff --git a/drivers/gpu/drm/virtio/Makefile b/drivers/gpu/drm/virtio/Makefile
> index b99fa4a73b68..24c7ebe87032 100644
> --- a/drivers/gpu/drm/virtio/Makefile
> +++ b/drivers/gpu/drm/virtio/Makefile
> @@ -4,8 +4,11 @@
> # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
>
> virtio-gpu-y := virtgpu_drv.o virtgpu_kms.o virtgpu_gem.o virtgpu_vram.o \
> - virtgpu_display.o virtgpu_vq.o \
> + virtgpu_vq.o \
> virtgpu_fence.o virtgpu_object.o virtgpu_debugfs.o virtgpu_plane.o \
> virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o
>
> +virtio-gpu-$(CONFIG_DRM_VIRTIO_GPU_KMS) += \
> + virtgpu_display.o
> +
> obj-$(CONFIG_DRM_VIRTIO_GPU) += virtio-gpu.o
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index ae97b98750b6..9cb7d6dd3da6 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -172,7 +172,11 @@ MODULE_AUTHOR("Alon Levy");
> DEFINE_DRM_GEM_FOPS(virtio_gpu_driver_fops);
>
> static const struct drm_driver driver = {
> - .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_RENDER | DRIVER_ATOMIC,
> + .driver_features =
> +#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
> + DRIVER_MODESET | DRIVER_ATOMIC |
> +#endif
> + DRIVER_GEM | DRIVER_RENDER,
> .open = virtio_gpu_driver_open,
> .postclose = virtio_gpu_driver_postclose,
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index af6ffb696086..ffe8faf67247 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -426,8 +426,18 @@ virtio_gpu_cmd_set_scanout_blob(struct virtio_gpu_device *vgdev,
> uint32_t x, uint32_t y);
>
> /* virtgpu_display.c */
> +#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
> int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev);
> void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev);
> +#else
> +static inline int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev)
> +{
> + return 0;
> +}
> +static inline void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev)
> +{
> +}
> +#endif
>
> /* virtgpu_plane.c */
> uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc);
> diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
> index 27b7f14dae89..293e6f0bf133 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_kms.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
> @@ -161,9 +161,11 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
> if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_VIRGL))
> vgdev->has_virgl_3d = true;
> #endif
> +#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
> if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_EDID)) {
> vgdev->has_edid = true;
> }
> +#endif
> if (virtio_has_feature(vgdev->vdev, VIRTIO_RING_F_INDIRECT_DESC)) {
> vgdev->has_indirect = true;
> }
> @@ -218,6 +220,7 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
> goto err_vbufs;
> }
>
> +#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
> /* get display info */
> virtio_cread_le(vgdev->vdev, struct virtio_gpu_config,
> num_scanouts, &num_scanouts);
> @@ -229,6 +232,7 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
> goto err_scanouts;
> }
> DRM_INFO("number of scanouts: %d\n", num_scanouts);
> +#endif
>
> virtio_cread_le(vgdev->vdev, struct virtio_gpu_config,
> num_capsets, &num_capsets);
> @@ -246,10 +250,12 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
> virtio_gpu_get_capsets(vgdev, num_capsets);
> if (vgdev->has_edid)
> virtio_gpu_cmd_get_edids(vgdev);
> +#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
> virtio_gpu_cmd_get_display_info(vgdev);
> virtio_gpu_notify(vgdev);
> wait_event_timeout(vgdev->resp_wq, !vgdev->display_info_pending,
> 5 * HZ);
> +#endif
> return 0;
>
> err_scanouts:

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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