Re: [PATCH 3/4] drm: Add helper for simple display pipeline

Daniel Vetter
2016-05-05T16:45:35Z

On Thu, May 05, 2016 at 03:24:33PM +0200, Noralf Trønnes wrote:
> Provides helper functions for drivers that have a simple display
> pipeline. Plane, crtc and encoder are collapsed into one entity.
>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

When resubmitting a patch please always have a per-patch changelog of what
you've done. Otherwise you force reviewers to remember they looked at this
already, dig out the old mail and compare ;-)

> ---
> drivers/gpu/drm/Kconfig | 7 ++
> drivers/gpu/drm/Makefile | 1 +
> drivers/gpu/drm/drm_simple_kms_helper.c | 157 ++++++++++++++++++++++++++++++++
> include/drm/drm_simple_kms_helper.h | 88 ++++++++++++++++++

Please also add a new section (next to all the ones for the other kms
helpers) in Documentation/DocBook/gpu.tmpl and pull your kerneldoc in.
Please also add a short overview kernel doc section to the .c file (Using
the DOC: header) and also pull that into the overall gpu docs.

You can check the results using

$ make htmldocs

> 4 files changed, 253 insertions(+)
> create mode 100644 drivers/gpu/drm/drm_simple_kms_helper.c
> create mode 100644 include/drm/drm_simple_kms_helper.h
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 16e4c21..ff9f480 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -39,6 +39,13 @@ config DRM_KMS_HELPER
> help
> CRTC helpers for KMS drivers.
>
> +config DRM_SIMPLE_KMS_HELPER
> + tristate
> + depends on DRM
> + select DRM_KMS_HELPER
> + help
> + Helpers for very simple KMS drivers.
> +
> config DRM_KMS_FB_HELPER
> bool
> depends on DRM_KMS_HELPER
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 43c2abf..7e99923 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -31,6 +31,7 @@ drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
> drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
>
> obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
> +obj-$(CONFIG_DRM_SIMPLE_KMS_HELPER) += drm_simple_kms_helper.o
>
> CFLAGS_drm_trace_points.o := -I$(src)
>
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> new file mode 100644
> index 0000000..c8725bb
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -0,0 +1,157 @@
> +/*
> + * Copyright (C) 2016 Noralf Trønnes
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <drm/drmP.h>
> +#include <drm/drm_atomic.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_crtc_helper.h>
> +#include <drm/drm_plane_helper.h>
> +#include <drm/drm_simple_kms_helper.h>
> +#include <linux/slab.h>
> +
> +static const struct drm_encoder_funcs drm_simple_kms_encoder_funcs = {
> + .destroy = drm_encoder_cleanup,
> +};
> +
> +static void drm_simple_kms_crtc_enable(struct drm_crtc *crtc)
> +{
> + struct drm_simple_display_pipe *pipe;
> +
> + pipe = container_of(crtc, struct drm_simple_display_pipe, crtc);
> + if (!pipe->funcs || !pipe->funcs->enable)
> + return;
> +
> + pipe->funcs->enable(pipe, crtc->state);
> +}
> +
> +static void drm_simple_kms_crtc_disable(struct drm_crtc *crtc)
> +{
> + struct drm_simple_display_pipe *pipe;
> +
> + pipe = container_of(crtc, struct drm_simple_display_pipe, crtc);
> + if (!pipe->funcs || !pipe->funcs->disable)
> + return;
> +
> + pipe->funcs->disable(pipe);
> +}
> +
> +static const struct drm_crtc_helper_funcs drm_simple_kms_crtc_helper_funcs = {
> + .disable = drm_simple_kms_crtc_disable,
> + .enable = drm_simple_kms_crtc_enable,
> +};
> +
> +static const struct drm_crtc_funcs drm_simple_kms_crtc_funcs = {
> + .reset = drm_atomic_helper_crtc_reset,
> + .destroy = drm_crtc_cleanup,
> + .set_config = drm_atomic_helper_set_config,
> + .page_flip = drm_atomic_helper_page_flip,
> + .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
> +};
> +
> +static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> + struct drm_plane_state *pstate)
> +{
> + struct drm_simple_display_pipe *pipe;
> + struct drm_crtc_state *cstate;
> +
> + pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> + if (!pipe->funcs || !pipe->funcs->check)
> + return 0;
> +
> + cstate = drm_atomic_get_existing_crtc_state(pstate->state,
> + &pipe->crtc);
> +
> + return pipe->funcs->check(pipe, pstate, cstate);
> +}
> +
> +static void drm_simple_kms_plane_atomic_update(struct drm_plane *plane,
> + struct drm_plane_state *pstate)
> +{
> + struct drm_simple_display_pipe *pipe;
> +
> + pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> + if (!pipe->funcs || !pipe->funcs->update)
> + return;
> +
> + pipe->funcs->update(pipe, pstate);
> +}
> +
> +static const struct drm_plane_helper_funcs drm_simple_kms_plane_helper_funcs = {
> + .atomic_check = drm_simple_kms_plane_atomic_check,
> + .atomic_update = drm_simple_kms_plane_atomic_update,
> +};
> +
> +static const struct drm_plane_funcs drm_simple_kms_plane_funcs = {
> + .update_plane = drm_atomic_helper_update_plane,
> + .disable_plane = drm_atomic_helper_disable_plane,
> + .destroy = drm_plane_cleanup,
> + .reset = drm_atomic_helper_plane_reset,
> + .atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_plane_destroy_state,
> +};
> +
> +/**
> + * drm_simple_display_pipe_init - Initialize a simple display pipeline
> + * @dev: DRM device
> + * @pipe: simple display pipe object to initialize
> + * @funcs: callbacks for the display pipe
> + * @formats: array of supported formats (%DRM_FORMAT_*)
> + * @format_count: number of elements in @formats
> + * @connector: connector to attach and register
> + *
> + * Sets up a display pipeline which consist of a really simple
> + * plane-crtc-encoder pipe coupled with the provided connector.

need to specify that @funcs is optional.

> + *
> + * Returns:
> + * Zero on success, error code on failure.

"_negative_ error code"
> + */
> +int drm_simple_display_pipe_init(struct drm_device *dev,
> + struct drm_simple_display_pipe *pipe,
> + struct drm_simple_display_pipe_funcs *funcs,
> + const uint32_t *formats,
> + unsigned int format_count,
> + struct drm_connector *connector)
> +{
> + struct drm_encoder *encoder = &pipe->encoder;
> + struct drm_plane *plane = &pipe->plane;
> + struct drm_crtc *crtc = &pipe->crtc;
> + int ret;
> +
> + pipe->funcs = funcs;
> +
> + drm_plane_helper_add(plane, &drm_simple_kms_plane_helper_funcs);
> + ret = drm_universal_plane_init(dev, plane, 0,
> + &drm_simple_kms_plane_funcs,
> + formats, format_count,
> + DRM_PLANE_TYPE_PRIMARY, NULL);
> + if (ret)
> + return ret;
> +
> + drm_crtc_helper_add(crtc, &drm_simple_kms_crtc_helper_funcs);
> + ret = drm_crtc_init_with_planes(dev, crtc, plane, NULL,
> + &drm_simple_kms_crtc_funcs, NULL);
> + if (ret)
> + return ret;
> +
> + encoder->possible_crtcs = 1 << drm_crtc_index(crtc);
> + ret = drm_encoder_init(dev, encoder, &drm_simple_kms_encoder_funcs,
> + DRM_MODE_ENCODER_NONE, NULL);
> + if (ret)
> + return ret;
> +
> + ret = drm_mode_connector_attach_encoder(connector, encoder);
> + if (ret)
> + return ret;
> +
> + return drm_connector_register(connector);
> +}
> +EXPORT_SYMBOL(drm_simple_display_pipe_init);
> +
> +MODULE_LICENSE("GPL");
> diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
> new file mode 100644
> index 0000000..69eac94
> --- /dev/null
> +++ b/include/drm/drm_simple_kms_helper.h
> @@ -0,0 +1,88 @@
> +/*
> + * Copyright (C) 2016 Noralf Trønnes
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#ifndef __LINUX_DRM_SIMPLE_KMS_HELPER_H
> +#define __LINUX_DRM_SIMPLE_KMS_HELPER_H
> +
> +struct drm_simple_display_pipe;
> +
> +/**
> + * struct drm_simple_display_pipe_funcs - helper operations for a simple
> + * display pipeline
> + */
> +struct drm_simple_display_pipe_funcs {
> + /**
> + * @enable:
> + *
> + * This function should be used to enable the pipeline.
> + * It is called when the underlying crtc is enabled.

Please add boilerplate to all these hooks along the lines of:

"This hook is optional."

Besides that little bit of polish looks all good to me.
-Daniel

> + */
> + void (*enable)(struct drm_simple_display_pipe *pipe,
> + struct drm_crtc_state *crtc_state);
> + /**
> + * @disable:
> + *
> + * This function should be used to disable the pipeline.
> + * It is called when the underlying crtc is disabled.
> + */
> + void (*disable)(struct drm_simple_display_pipe *pipe);
> +
> + /**
> + * @check:
> + *
> + * This function is called in the check phase of an atomic update,
> + * specifically when the underlying plane is checked.
> + *
> + * RETURNS:
> + *
> + * 0 on success, -EINVAL if the state or the transition can't be
> + * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
> + * attempt to obtain another state object ran into a &drm_modeset_lock
> + * deadlock.
> + */
> + int (*check)(struct drm_simple_display_pipe *pipe,
> + struct drm_plane_state *plane_state,
> + struct drm_crtc_state *crtc_state);
> + /**
> + * @update:
> + *
> + * This function is called when the underlying plane state is updated.
> + */
> + void (*update)(struct drm_simple_display_pipe *pipe,
> + struct drm_plane_state *plane_state);
> +};
> +
> +/**
> + * struct drm_simple_display_pipe - simple display pipeline
> + * @crtc: CRTC control structure
> + * @plane: Plane control structure
> + * @encoder: Encoder control structure
> + * @connector: Connector control structure
> + * @funcs: Pipeline control functions (optional)
> + *
> + * Simple display pipeline with plane, crtc and encoder collapsed into one
> + * entity.
> + */
> +struct drm_simple_display_pipe {
> + struct drm_crtc crtc;
> + struct drm_plane plane;
> + struct drm_encoder encoder;
> + struct drm_connector *connector;
> +
> + struct drm_simple_display_pipe_funcs *funcs;
> +};
> +
> +int drm_simple_display_pipe_init(struct drm_device *dev,
> + struct drm_simple_display_pipe *pipe,
> + struct drm_simple_display_pipe_funcs *funcs,
> + const uint32_t *formats,
> + unsigned int format_count,
> + struct drm_connector *connector);
> +
> +#endif /* __LINUX_DRM_SIMPLE_KMS_HELPER_H */
> --
> 2.2.2
>

--
Daniel Vetter
Software Engineer, Intel Corporation