Re: [RFC v2 3/8] drm: Add helper for simple kms drivers

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Apr 08, 2016 at 07:05:05PM +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>

Looks good. A few comments below, but the big thing is adding kerneldoc
and cross-referencing it (e.g. from drm_panel to drm_panel_connector).
-Daniel

> ---
>  drivers/gpu/drm/Kconfig                 |   7 +
>  drivers/gpu/drm/Makefile                |   1 +
>  drivers/gpu/drm/drm_simple_kms_helper.c | 262 ++++++++++++++++++++++++++++++++
>  include/drm/drm_simple_kms_helper.h     |  44 ++++++
>  4 files changed, 314 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 8ae7ab6..cb62cd9 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -31,6 +31,13 @@ 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 61766de..ea9bf59 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -28,6 +28,7 @@ drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
>  drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.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..e193f7db
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -0,0 +1,262 @@
> +/*
> + * 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_helper.h>
> +#include <drm/drm_crtc_helper.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_plane_helper.h>
> +#include <drm/drm_simple_kms_helper.h>
> +#include <linux/slab.h>
> +
> +struct drm_simple_kms_connector {
> +	struct drm_connector base;
> +	struct drm_panel *panel;
> +};
> +
> +static inline struct drm_simple_kms_connector *
> +to_simple_connector(struct drm_connector *connector)
> +{
> +	return container_of(connector, struct drm_simple_kms_connector, base);
> +}
> +
> +static int drm_simple_kms_connector_get_modes(struct drm_connector *connector)
> +{
> +	return drm_panel_get_modes(to_simple_connector(connector)->panel);
> +}
> +
> +static struct drm_encoder *
> +drm_simple_kms_connector_best_encoder(struct drm_connector *connector)
> +{
> +	return drm_encoder_find(connector->dev, connector->encoder_ids[0]);
> +}

I think this would be useful for atomic drivers in general. I even thought
we have it already somewhere ...

> +
> +static const struct drm_connector_helper_funcs drm_simple_kms_connector_helper_funcs = {
> +	.get_modes = drm_simple_kms_connector_get_modes,
> +	.best_encoder = drm_simple_kms_connector_best_encoder,
> +};
> +
> +static enum drm_connector_status
> +drm_simple_kms_connector_detect(struct drm_connector *connector, bool force)
> +{
> +	if (drm_device_is_unplugged(connector->dev))
> +		return connector_status_disconnected;
> +
> +	return connector->status;
> +}
> +
> +static void drm_simple_kms_connector_destroy(struct drm_connector *connector)
> +{
> +	struct drm_simple_kms_connector *panel_connector;
> +
> +	panel_connector = to_simple_connector(connector);
> +	drm_panel_detach(panel_connector->panel);
> +	drm_panel_remove(panel_connector->panel);
> +	drm_connector_unregister(connector);
> +	drm_connector_cleanup(connector);
> +	kfree(panel_connector);
> +}
> +
> +static const struct drm_connector_funcs drm_simple_kms_connector_funcs = {
> +	.dpms = drm_atomic_helper_connector_dpms,
> +	.reset = drm_atomic_helper_connector_reset,
> +	.detect = drm_simple_kms_connector_detect,
> +	.fill_modes = drm_helper_probe_single_connector_modes,
> +	.destroy = drm_simple_kms_connector_destroy,
> +	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +};

drm_simple_kms_panel_connector is toooooooooooo long ;-) What about just
drm_panel_connector instead? Also not entirely sure whether this is best
placed here, or better in drm_panel.c, or maybe even in a new
drm_panel_helper.c.

Imo drm_panel_connector and drm_simple_display_pipe should work as
orthogonal helpers.

Or 3rd option: You just expose the above helpers for detect/get_modes
only.

> +
> +/**
> + * drm_simple_kms_panel_connector_create - Create simple connector for panel
> + * @dev: DRM device
> + * @panel: DRM panel
> + * @connector_type: user visible type of the connector
> + *
> + * Creates a simple connector for a panel.
> + * The panel needs to provide a get_modes() function.
> + *
> + * Returns:
> + * Pointer to new connector or ERR_PTR on failure.
> + */
> +struct drm_connector *
> +drm_simple_kms_panel_connector_create(struct drm_device *dev,
> +				      struct drm_panel *panel,
> +				      int connector_type)
> +{
> +	struct drm_simple_kms_connector *panel_connector;
> +	struct drm_connector *connector;
> +	int ret;
> +
> +	panel_connector = kzalloc(sizeof(*panel_connector), GFP_KERNEL);
> +	if (!panel_connector)
> +		return ERR_PTR(-ENOMEM);
> +
> +	panel_connector->panel = panel;
> +	connector = &panel_connector->base;
> +	drm_connector_helper_add(connector, &drm_simple_kms_connector_helper_funcs);
> +	ret = drm_connector_init(dev, connector, &drm_simple_kms_connector_funcs,
> +				 connector_type);
> +	if (ret) {
> +		kfree(panel_connector);
> +		return ERR_PTR(ret);
> +	}
> +
> +	connector->status = connector_status_connected;
> +	drm_panel_init(panel);
> +	drm_panel_add(panel);
> +	drm_panel_attach(panel, connector);
> +
> +	return connector;
> +}
> +EXPORT_SYMBOL(drm_simple_kms_panel_connector_create);
> +
> +static void drm_simple_kms_encoder_disable(struct drm_encoder *encoder)
> +{
> +}
> +
> +static void drm_simple_kms_encoder_enable(struct drm_encoder *encoder)
> +{
> +}
> +
> +static int drm_simple_kms_encoder_atomic_check(struct drm_encoder *encoder,
> +					struct drm_crtc_state *crtc_state,
> +					struct drm_connector_state *conn_state)
> +{
> +	return 0;
> +}

Above dummy functions shouldn't be necessary.

> +
> +static const struct drm_encoder_helper_funcs drm_simple_kms_encoder_helper_funcs = {
> +	.disable = drm_simple_kms_encoder_disable,
> +	.enable = drm_simple_kms_encoder_enable,
> +	.atomic_check = drm_simple_kms_encoder_atomic_check,
> +};
> +
> +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 void drm_simple_kms_plane_atomic_update(struct drm_plane *plane,
> +					struct drm_plane_state *old_state)
> +{
> +	struct drm_simple_display_pipe *pipe;
> +
> +	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> +	if (!pipe->funcs || !pipe->funcs->plane_update)
> +		return;
> +
> +	pipe->funcs->plane_update(pipe, old_state);
> +}
> +
> +static const struct drm_plane_helper_funcs drm_simple_kms_plane_helper_funcs = {
> +	.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 pipe
> + * @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 pipe which consist of a really simple plane-crtc-encoder
> + * pipe coupled with the provided connector.
> + *
> + * Returns:
> + * Zero on success, error code on failure.
> + */
> +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);
> +	drm_encoder_helper_add(encoder, &drm_simple_kms_encoder_helper_funcs);
> +	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..0f7461b
> --- /dev/null
> +++ b/include/drm/drm_simple_kms_helper.h
> @@ -0,0 +1,44 @@
> +/*
> + * 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 {
> +	void (*enable)(struct drm_simple_display_pipe *pipe,
> +		       struct drm_crtc_state *crtc_state);
> +	void (*disable)(struct drm_simple_display_pipe *pipe);
> +	void (*plane_update)(struct drm_simple_display_pipe *pipe,
> +			     struct drm_plane_state *plane_state);

On 2nd thought maybe we want an atomic_check in here too, with same
parameters *pipe, *crtc_state and *plane_state (so that it's useful for
both plane-only updates and modeset changes).

> +};
> +
> +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);
> +struct drm_connector *
> +drm_simple_kms_panel_connector_create(struct drm_device *dev,
> +				      struct drm_panel *panel,
> +				      int connector_type);
> +
> +
> +
> +#endif /* __LINUX_DRM_SIMPLE_KMS_HELPER_H */
> -- 
> 2.2.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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