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Date: Tue, 17 May 2016 09:05:01 +0200
From: Daniel Vetter <daniel@ffwll.ch>
To: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Cc: Noralf =?iso-8859-1?Q?Tr=F8nnes?= <noralf@tronnes.org>, jsarha@ti.com,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/3] drm: Add helper for simple display pipeline
Message-ID: <20160517070501.GJ27098@phenom.ffwll.local>
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On Thu, May 12, 2016 at 09:36:14PM +0300, Ville Syrjälä wrote:
> On Thu, May 12, 2016 at 08:25:23PM +0200, Noralf Trønnes wrote:
> > Provides helper functions for drivers that have a simple display
> > pipeline. Plane, crtc and encoder are collapsed into one entity.
> > 
> > Cc: jsarha@ti.com
> > Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> > ---
> > 
> > Changes since v3:
> > - (struct drm_simple_display_pipe *)->funcs should be const
> > 
> > Changes since v2:
> > - Drop Kconfig knob DRM_KMS_HELPER
> > - Expand documentation
> > 
> > Changes since v1:
> > - Add DOC header and add to gpu.tmpl
> > - Fix docs: @funcs is optional, "negative error code",
> >   "This hook is optional."
> > - Add checks to drm_simple_kms_plane_atomic_check()
> > 
> >  Documentation/DocBook/gpu.tmpl          |   6 +
> >  drivers/gpu/drm/Makefile                |   2 +-
> >  drivers/gpu/drm/drm_simple_kms_helper.c | 208 ++++++++++++++++++++++++++++++++
> >  include/drm/drm_simple_kms_helper.h     |  94 +++++++++++++++
> >  4 files changed, 309 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/gpu/drm/drm_simple_kms_helper.c
> >  create mode 100644 include/drm/drm_simple_kms_helper.h
> > 
> > diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> > index 4a0c599..cf3f5a8 100644
> > --- a/Documentation/DocBook/gpu.tmpl
> > +++ b/Documentation/DocBook/gpu.tmpl
> > @@ -1693,6 +1693,12 @@ void intel_crt_init(struct drm_device *dev)
> >  !Edrivers/gpu/drm/drm_panel.c
> >  !Pdrivers/gpu/drm/drm_panel.c drm panel
> >      </sect2>
> > +    <sect2>
> > +      <title>Simple KMS Helper Reference</title>
> > +!Iinclude/drm/drm_simple_kms_helper.h
> > +!Edrivers/gpu/drm/drm_simple_kms_helper.c
> > +!Pdrivers/gpu/drm/drm_simple_kms_helper.c overview
> > +    </sect2>
> >    </sect1>
> > 
> >    <!-- Internals: kms properties -->
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> > index 2bd3e5a..31b85df5 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
> > 
> >  drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
> >  		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
> > -		drm_kms_helper_common.o
> > +		drm_kms_helper_common.o drm_simple_kms_helper.o
> > 
> >  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> >  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> > 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..d45417a
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > @@ -0,0 +1,208 @@
> > +/*
> > + * 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>
> > +
> > +/**
> > + * DOC: overview
> > + *
> > + * This helper library provides helpers for drivers for simple display
> > + * hardware.
> > + *
> > + * drm_simple_display_pipe_init() initializes a simple display pipeline
> > + * which has only one full-screen scanout buffer feeding one output. The
> > + * pipeline is represented by struct &drm_simple_display_pipe and binds
> > + * together &drm_plane, &drm_crtc and &drm_encoder structures into one fixed
> > + * entity. Some flexibility for code reuse is provided through a separately
> > + * allocated &drm_connector object and supporting optional &drm_bridge
> > + * encoder drivers.
> > + */
> > +
> > +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 *plane_state)
> > +{
> > +	struct drm_rect src = {
> > +		.x1 = plane_state->src_x,
> > +		.y1 = plane_state->src_y,
> > +		.x2 = plane_state->src_x + plane_state->src_w,
> > +		.y2 = plane_state->src_y + plane_state->src_h,
> > +	};
> > +	struct drm_rect dest = {
> > +		.x1 = plane_state->crtc_x,
> > +		.y1 = plane_state->crtc_y,
> > +		.x2 = plane_state->crtc_x + plane_state->crtc_w,
> > +		.y2 = plane_state->crtc_y + plane_state->crtc_h,
> > +	};
> > +	struct drm_rect clip = { 0 };
> > +	struct drm_simple_display_pipe *pipe;
> > +	struct drm_crtc_state *crtc_state;
> > +	bool visible;
> > +	int ret;
> > +
> > +	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> > +	crtc_state = drm_atomic_get_existing_crtc_state(plane_state->state,
> > +							&pipe->crtc);
> > +	if (crtc_state->enable != !!plane_state->crtc)
> > +		return -EINVAL; /* plane must match crtc enable state */
> > +
> > +	if (!crtc_state->enable)
> > +		return 0; /* nothing to check when disabling or disabled */
> > +
> > +	clip.x2 = crtc_state->adjusted_mode.hdisplay;
> > +	clip.y2 = crtc_state->adjusted_mode.vdisplay;
> > +	ret = drm_plane_helper_check_update(plane, &pipe->crtc,
> > +					    plane_state->fb,
> > +					    &src, &dest, &clip,
> > +					    DRM_PLANE_HELPER_NO_SCALING,
> > +					    DRM_PLANE_HELPER_NO_SCALING,
> > +					    false, true, &visible);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (!visible)
> > +		return -EINVAL;
> > +
> > +	if (!pipe->funcs || !pipe->funcs->check)
> > +		return 0;
> > +
> > +	return pipe->funcs->check(pipe, plane_state, crtc_state);
> > +}
> 
> What's anyone supposed to do with this when the clipped coordinates
> aren't even passed/stored anywhere?

It disallows positioning and scaling, so shouldn't ever need to have the
clipped area?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch