Hi

Am 25.07.21 um 21:49 schrieb Sam Ravnborg:
Hi Thomas,

On Sun, Jul 25, 2021 at 07:44:34PM +0200, Thomas Zimmermann wrote:
DRM uses a magic number of 4 for the maximum number of planes per color
format. Declare this constant via DRM_FORMAT_MAX_PLANES and update the
related code. Some code depends on the length of arrays that are now
declared with DRM_FORMAT_MAX_PLANES. Convert it from '4' to ARRAY_SIZE.

v2:
        * mention usage of ARRAY_SIZE() in the commit message (Maxime)
        * also fix error handling in drm_gem_fb_init_with_funcs()
          (kernel test robot)
        * include <drm/drm_fourcc.h> for DRM_FORMAT_MAX_PLANES

Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>

One nit below.
Reviewed-by: Sam Ravnborg <s...@ravnborg.org>

Thanks a lot for your reviews.


---
  drivers/gpu/drm/drm_gem_framebuffer_helper.c | 19 +++++++++++--------
  include/drm/drm_fourcc.h                     | 13 +++++++++----
  include/drm/drm_framebuffer.h                |  8 ++++----
  include/drm/drm_gem_atomic_helper.h          |  3 ++-
  4 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c 
b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index 67bc9edc1d98..421e029a6b3e 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -48,7 +48,7 @@
  struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
                                          unsigned int plane)
  {
-       if (plane >= 4)
+       if (plane >= ARRAY_SIZE(fb->obj))
                return NULL;
return fb->obj[plane];
@@ -62,7 +62,8 @@ drm_gem_fb_init(struct drm_device *dev,
                 struct drm_gem_object **obj, unsigned int num_planes,
                 const struct drm_framebuffer_funcs *funcs)
  {
-       int ret, i;
+       unsigned int i;
+       int ret;
drm_helper_mode_fill_fb_struct(dev, fb, mode_cmd);

This change looks accidental/unrelated.
But I guess it is to be consistent in use of unsigned int when
iterating the array.

Indeed. The current code uses a mixture of signed and unsigned types in several places. DRM_FORMAT_MAX_PLANES is defined as unsigned, so I updated all the related code accordingly.

Best regards
Thomas


@@ -86,9 +87,9 @@ drm_gem_fb_init(struct drm_device *dev,
   */
  void drm_gem_fb_destroy(struct drm_framebuffer *fb)
  {
-       int i;
+       size_t i;
- for (i = 0; i < 4; i++)
+       for (i = 0; i < ARRAY_SIZE(fb->obj); i++)
                drm_gem_object_put(fb->obj[i]);
drm_framebuffer_cleanup(fb);
@@ -145,8 +146,9 @@ int drm_gem_fb_init_with_funcs(struct drm_device *dev,
                               const struct drm_framebuffer_funcs *funcs)
  {
        const struct drm_format_info *info;
-       struct drm_gem_object *objs[4];
-       int ret, i;
+       struct drm_gem_object *objs[DRM_FORMAT_MAX_PLANES];
+       unsigned int i;
+       int ret;
info = drm_get_format_info(dev, mode_cmd);
        if (!info) {
@@ -187,9 +189,10 @@ int drm_gem_fb_init_with_funcs(struct drm_device *dev,
        return 0;
err_gem_object_put:
-       for (i--; i >= 0; i--)
+       while (i > 0) {
+               --i;
                drm_gem_object_put(objs[i]);
-
+       }
        return ret;
  }
  EXPORT_SYMBOL_GPL(drm_gem_fb_init_with_funcs);
diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
index 3b138d4ae67e..22aa64d07c79 100644
--- a/include/drm/drm_fourcc.h
+++ b/include/drm/drm_fourcc.h
@@ -25,6 +25,11 @@
  #include <linux/types.h>
  #include <uapi/drm/drm_fourcc.h>
+/**
+ * DRM_FORMAT_MAX_PLANES - maximum number of planes a DRM format can have
+ */
+#define DRM_FORMAT_MAX_PLANES  4u
+
  /*
   * DRM formats are little endian.  Define host endian variants for the
   * most common formats here, to reduce the #ifdefs needed in drivers.
@@ -78,7 +83,7 @@ struct drm_format_info {
                 * triplet @char_per_block, @block_w, @block_h for better
                 * describing the pixel format.
                 */
-               u8 cpp[4];
+               u8 cpp[DRM_FORMAT_MAX_PLANES];
/**
                 * @char_per_block:
@@ -104,7 +109,7 @@ struct drm_format_info {
                 * information from their drm_mode_config.get_format_info hook
                 * if they want the core to be validating the pitch.
                 */
-               u8 char_per_block[4];
+               u8 char_per_block[DRM_FORMAT_MAX_PLANES];
        };
/**
@@ -113,7 +118,7 @@ struct drm_format_info {
         * Block width in pixels, this is intended to be accessed through
         * drm_format_info_block_width()
         */
-       u8 block_w[4];
+       u8 block_w[DRM_FORMAT_MAX_PLANES];
/**
         * @block_h:
@@ -121,7 +126,7 @@ struct drm_format_info {
         * Block height in pixels, this is intended to be accessed through
         * drm_format_info_block_height()
         */
-       u8 block_h[4];
+       u8 block_h[DRM_FORMAT_MAX_PLANES];
/** @hsub: Horizontal chroma subsampling factor */
        u8 hsub;
diff --git a/include/drm/drm_framebuffer.h b/include/drm/drm_framebuffer.h
index be658ebbec72..f67c5b7bcb68 100644
--- a/include/drm/drm_framebuffer.h
+++ b/include/drm/drm_framebuffer.h
@@ -27,12 +27,12 @@
  #include <linux/list.h>
  #include <linux/sched.h>
+#include <drm/drm_fourcc.h>
  #include <drm/drm_mode_object.h>
struct drm_clip_rect;
  struct drm_device;
  struct drm_file;
-struct drm_format_info;
  struct drm_framebuffer;
  struct drm_gem_object;
@@ -147,7 +147,7 @@ struct drm_framebuffer {
         * @pitches: Line stride per buffer. For userspace created object this
         * is copied from drm_mode_fb_cmd2.
         */
-       unsigned int pitches[4];
+       unsigned int pitches[DRM_FORMAT_MAX_PLANES];
        /**
         * @offsets: Offset from buffer start to the actual pixel data in bytes,
         * per buffer. For userspace created object this is copied from
@@ -165,7 +165,7 @@ struct drm_framebuffer {
         * data (even for linear buffers). Specifying an x/y pixel offset is
         * instead done through the source rectangle in &struct drm_plane_state.
         */
-       unsigned int offsets[4];
+       unsigned int offsets[DRM_FORMAT_MAX_PLANES];
        /**
         * @modifier: Data layout modifier. This is used to describe
         * tiling, or also special layouts (like compression) of auxiliary
@@ -210,7 +210,7 @@ struct drm_framebuffer {
         * This is used by the GEM framebuffer helpers, see e.g.
         * drm_gem_fb_create().
         */
-       struct drm_gem_object *obj[4];
+       struct drm_gem_object *obj[DRM_FORMAT_MAX_PLANES];
  };
#define obj_to_fb(x) container_of(x, struct drm_framebuffer, base)
diff --git a/include/drm/drm_gem_atomic_helper.h 
b/include/drm/drm_gem_atomic_helper.h
index d82c23622156..f9f8b6f0494a 100644
--- a/include/drm/drm_gem_atomic_helper.h
+++ b/include/drm/drm_gem_atomic_helper.h
@@ -5,6 +5,7 @@
#include <linux/dma-buf-map.h> +#include <drm/drm_fourcc.h>
  #include <drm/drm_plane.h>
struct drm_simple_display_pipe;
@@ -40,7 +41,7 @@ struct drm_shadow_plane_state {
         * The memory mappings stored in map should be established in the 
plane's
         * prepare_fb callback and removed in the cleanup_fb callback.
         */
-       struct dma_buf_map map[4];
+       struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
  };
/**
--
2.32.0

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

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