Re: [linux-sunxi] Re: [PATCH v3 04/11] drm/sun4i: abstract the layer type

From: icenowy
Date: Wed Apr 05 2017 - 13:15:07 EST

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In reply to: Chen-Yu Tsai: "Re: [linux-sunxi] Re: [PATCH v3 04/11] drm/sun4i: abstract the layer type"
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å 2017-04-05 10:27ïChen-Yu Tsai åéï

On Wed, Apr 5, 2017 at 3:53 AM, Icenowy Zheng <icenowy@xxxxxxx> wrote:

å 2017å04æ05æ 03:28, Sean Paul åé:

On Thu, Mar 30, 2017 at 03:46:06AM +0800, Icenowy Zheng wrote:

As we are going to add support for the Allwinner DE2 Mixer in sun4i-drm
driver, we will finally have two types of layer.

Abstract the layer type to void * and a ops struct, which contains the
only function used by crtc -- get the drm_plane struct of the layer.

Signed-off-by: Icenowy Zheng <icenowy@xxxxxxx>
---
Refactored patch in v3.

drivers/gpu/drm/sun4i/sun4i_crtc.c | 19 +++++++++++--------
drivers/gpu/drm/sun4i/sun4i_crtc.h | 3 ++-
drivers/gpu/drm/sun4i/sun4i_layer.c | 19 ++++++++++++++++++-
drivers/gpu/drm/sun4i/sun4i_layer.h | 2 +-
drivers/gpu/drm/sun4i/sunxi_layer.h | 17 +++++++++++++++++
5 files changed, 49 insertions(+), 11 deletions(-)
create mode 100644 drivers/gpu/drm/sun4i/sunxi_layer.h

diff --git a/drivers/gpu/drm/sun4i/sun4i_crtc.c
b/drivers/gpu/drm/sun4i/sun4i_crtc.c
index 3c876c3a356a..33854ee7f636 100644
--- a/drivers/gpu/drm/sun4i/sun4i_crtc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_crtc.c
@@ -29,6 +29,7 @@
#include "sun4i_crtc.h"
#include "sun4i_drv.h"
#include "sun4i_layer.h"
+#include "sunxi_layer.h"
#include "sun4i_tcon.h"

static void sun4i_crtc_atomic_begin(struct drm_crtc *crtc,
@@ -149,7 +150,7 @@ struct sun4i_crtc *sun4i_crtc_init(struct drm_device
*drm,
scrtc->tcon = tcon;

/* Create our layers */
- scrtc->layers = sun4i_layers_init(drm, scrtc->backend);
+ scrtc->layers = (void **)sun4i_layers_init(drm, scrtc);
if (IS_ERR(scrtc->layers)) {
dev_err(drm->dev, "Couldn't create the planes\n");
return NULL;
@@ -157,14 +158,15 @@ struct sun4i_crtc *sun4i_crtc_init(struct
drm_device *drm,

/* find primary and cursor planes for drm_crtc_init_with_planes
*/
for (i = 0; scrtc->layers[i]; i++) {
- struct sun4i_layer *layer = scrtc->layers[i];
+ void *layer = scrtc->layers[i];
+ struct drm_plane *plane =
scrtc->layer_ops->get_plane(layer);

- switch (layer->plane.type) {
+ switch (plane->type) {
case DRM_PLANE_TYPE_PRIMARY:
- primary = &layer->plane;
+ primary = plane;
break;
case DRM_PLANE_TYPE_CURSOR:
- cursor = &layer->plane;
+ cursor = plane;
break;
default:
break;
@@ -190,10 +192,11 @@ struct sun4i_crtc *sun4i_crtc_init(struct
drm_device *drm,
/* Set possible_crtcs to this crtc for overlay planes */
for (i = 0; scrtc->layers[i]; i++) {
uint32_t possible_crtcs =
BIT(drm_crtc_index(&scrtc->crtc));
- struct sun4i_layer *layer = scrtc->layers[i];
+ void *layer = scrtc->layers[i];
+ struct drm_plane *plane =
scrtc->layer_ops->get_plane(layer);

- if (layer->plane.type == DRM_PLANE_TYPE_OVERLAY)
- layer->plane.possible_crtcs = possible_crtcs;
+ if (plane->type == DRM_PLANE_TYPE_OVERLAY)
+ plane->possible_crtcs = possible_crtcs;
}

return scrtc;
diff --git a/drivers/gpu/drm/sun4i/sun4i_crtc.h
b/drivers/gpu/drm/sun4i/sun4i_crtc.h
index 230cb8f0d601..a4036ee44cf8 100644
--- a/drivers/gpu/drm/sun4i/sun4i_crtc.h
+++ b/drivers/gpu/drm/sun4i/sun4i_crtc.h
@@ -19,7 +19,8 @@ struct sun4i_crtc {

struct sun4i_backend *backend;
struct sun4i_tcon *tcon;
- struct sun4i_layer **layers;
+ void **layers;
+ const struct sunxi_layer_ops *layer_ops;

I think you should probably take a different approach to abstract the
layer
type. How about creating

struct sunxi_layer {
struct drm_plane plane;
}

base and then subclassing that for sun4i and sun8i? By doing this you can
avoid
the nasty casting and you can also get rid of the get_plane() hook and
layer_ops.

For the situation that using ** things are easily to get weird.

That code could be reworked, by initializing the layers directly within
the crtc init code. If you look at rockchip's drm driver, you'll see
they do this. There is a good reason to do it this way, as you need
to first create the primary and cursor layers, pass them in when you
create the crtc, then initialize any additional layers with the
possible_crtcs bitmap.

I feel that it's still more proper to offload plane creation code
to *_layers_init function, as:

1. We cannot assume the cursor layer's
existance. In fact currently no code in sun4i-drm (including this
patchset) create a cursor layer.

2. The format of planes heavily depend on the engine type (
sun4i-backend or sun8i-mixer).

3. We should create planes according to the type of engine.
Currently the *_layers_init function is part of engine code (See my
Makefile change).

4. If we do so we will have two codes for plane creating -- one for
primary in sun4i_crtc_init, another for overlays in *_layers_init.

In our driver we are currently initializing all layers, then going
back and filling in possible_crtcs for the extra layers.

And as Maxime and I mentioned in the other thread, we don't really
need to keep a reference to **layers.

It's correct, layers doesn't need to be kept.

And the struct sunxi_layer refactor also makes sense.

Regards
ChenYu

Sean

};

static inline struct sun4i_crtc *drm_crtc_to_sun4i_crtc(struct drm_crtc
*crtc)
diff --git a/drivers/gpu/drm/sun4i/sun4i_layer.c
b/drivers/gpu/drm/sun4i/sun4i_layer.c
index f26bde5b9117..bc4a70d6968b 100644
--- a/drivers/gpu/drm/sun4i/sun4i_layer.c
+++ b/drivers/gpu/drm/sun4i/sun4i_layer.c
@@ -16,7 +16,9 @@
#include <drm/drmP.h>

#include "sun4i_backend.h"
+#include "sun4i_crtc.h"
#include "sun4i_layer.h"
+#include "sunxi_layer.h"

struct sun4i_plane_desc {
enum drm_plane_type type;
@@ -100,6 +102,17 @@ static const struct sun4i_plane_desc
sun4i_backend_planes[] = {
},
};

+static struct drm_plane *sun4i_layer_get_plane(void *layer)
+{
+ struct sun4i_layer *sun4i_layer = layer;
+
+ return &sun4i_layer->plane;
+}
+
+static const struct sunxi_layer_ops layer_ops = {
+ .get_plane = sun4i_layer_get_plane,
+};
+
static struct sun4i_layer *sun4i_layer_init_one(struct drm_device *drm,
struct sun4i_backend
*backend,
const struct
sun4i_plane_desc *plane)
@@ -129,9 +142,10 @@ static struct sun4i_layer
*sun4i_layer_init_one(struct drm_device *drm,
}

struct sun4i_layer **sun4i_layers_init(struct drm_device *drm,
- struct sun4i_backend *backend)
+ struct sun4i_crtc *crtc)
{
struct sun4i_layer **layers;
+ struct sun4i_backend *backend = crtc->backend;
int i;

layers = devm_kcalloc(drm->dev, ARRAY_SIZE(sun4i_backend_planes)
+ 1,
@@ -181,5 +195,8 @@ struct sun4i_layer **sun4i_layers_init(struct
drm_device *drm,
layers[i] = layer;
};

+ /* Assign layer ops to the CRTC */
+ crtc->layer_ops = &layer_ops;
+
return layers;
}
diff --git a/drivers/gpu/drm/sun4i/sun4i_layer.h
b/drivers/gpu/drm/sun4i/sun4i_layer.h
index 4be1f0919df2..425eea7b9e3b 100644
--- a/drivers/gpu/drm/sun4i/sun4i_layer.h
+++ b/drivers/gpu/drm/sun4i/sun4i_layer.h
@@ -27,6 +27,6 @@ plane_to_sun4i_layer(struct drm_plane *plane)
}

struct sun4i_layer **sun4i_layers_init(struct drm_device *drm,
- struct sun4i_backend *backend);
+ struct sun4i_crtc *crtc);

#endif /* _SUN4I_LAYER_H_ */
diff --git a/drivers/gpu/drm/sun4i/sunxi_layer.h
b/drivers/gpu/drm/sun4i/sunxi_layer.h
new file mode 100644
index 000000000000..d8838ec39299
--- /dev/null
+++ b/drivers/gpu/drm/sun4i/sunxi_layer.h
@@ -0,0 +1,17 @@
+/*
+ * Copyright (C) 2017 Icenowy Zheng <icenowy@xxxxxxxx>
+ *
+ * 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 _SUNXI_LAYER_H_
+#define _SUNXI_LAYER_H_
+
+struct sunxi_layer_ops {
+ struct drm_plane *(*get_plane)(void *layer);
+};
+
+#endif /* _SUNXI_LAYER_H_ */
--
2.12.0

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Next message: David Howells: "[PATCH 06/24] Add a sysrq option to exit secure boot mode"
Previous message: David Howells: "[PATCH 13/24] x86: Lock down IO port access when the kernel is locked down"
In reply to: Chen-Yu Tsai: "Re: [linux-sunxi] Re: [PATCH v3 04/11] drm/sun4i: abstract the layer type"
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