linux-kernel - [PATCH 1/2] drm/vkms: Create a type to check a function pointer validity

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Message-Id: <20240201-yuv-v1-1-3ca376f27632@bootlin.com>
Date: Thu, 01 Feb 2024 18:31:31 +0100
From: Louis Chauvet <louis.chauvet@...tlin.com>
To: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>, 
 Melissa Wen <melissa.srw@...il.com>, 
 Maíra Canal <mairacanal@...eup.net>, 
 Haneen Mohammed <hamohammed.sa@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, marcheu@...gle.com, seanpaul@...gle.com, 
 nicolejadeyee@...gle.com
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Louis Chauvet <louis.chauvet@...tlin.com>, thomas.petazzoni@...tlin.com, 
 miquel.raynal@...tlin.com
Subject: [PATCH 1/2] drm/vkms: Create a type to check a function pointer
 validity

Add the pixel_read_t type to check function prototype in structures
and functions.
It avoids casting to (void *) and at the same occasion allows the
compiler to check the type properly.

Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
---
 drivers/gpu/drm/vkms/vkms_drv.h     | 17 +++++++++++++++--
 drivers/gpu/drm/vkms/vkms_formats.c |  4 ++--
 drivers/gpu/drm/vkms/vkms_formats.h |  2 +-
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 51349a0c32d8..cb20bab26cae 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -48,6 +48,20 @@ struct vkms_writeback_job {
 	void (*pixel_write)(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel);
 };
 
+/**
+ * typedef pixel_read_t - These functions are used to read the pixels in the source frame, convert
+ * them to argb16 and write them to out_pixel.
+ * It assumes that src_pixels point to a valid pixel (not a block, or a block of 1x1 pixel)
+ *
+ * @src_pixels: Source pointer to a pixel
+ * @out_pixel: Pointer where to write the pixel value
+ * @encoding: Color encoding to use (mainly used for YUV formats)
+ * @range: Color range to use (mainly used for YUV formats)
+ */
+typedef void (*pixel_read_t)(u8 **src_pixels, int y,
+			     struct pixel_argb_u16 *out_pixel, enum drm_color_encoding enconding,
+			     enum drm_color_range range);
+
 /**
  * vkms_plane_state - Driver specific plane state
  * @base: base plane state
@@ -56,8 +70,7 @@ struct vkms_writeback_job {
 struct vkms_plane_state {
 	struct drm_shadow_plane_state base;
 	struct vkms_frame_info *frame_info;
-	void (*pixel_read)(u8 **src_buffer, struct pixel_argb_u16 *out_pixel,
-			   enum drm_color_encoding enconding, enum drm_color_range range);
+	pixel_read_t pixel_read;
 };
 
 struct vkms_plane {
diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
index e06bbd7c0a67..c6376db58d38 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -390,7 +390,7 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
 		wb->pixel_write(dst_pixels, &in_pixels[x]);
 }
 
-void *get_pixel_conversion_function(u32 format)
+pixel_read_t get_pixel_conversion_function(u32 format)
 {
 	switch (format) {
 	case DRM_FORMAT_ARGB8888:
@@ -420,7 +420,7 @@ void *get_pixel_conversion_function(u32 format)
 	case DRM_FORMAT_YVU444:
 		return &planar_yvu_to_argb_u16;
 	default:
-		return NULL;
+		return (pixel_read_t)NULL;
 	}
 }
 
diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h
index 0cf835292cec..04e31e126ab1 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.h
+++ b/drivers/gpu/drm/vkms/vkms_formats.h
@@ -5,7 +5,7 @@
 
 #include "vkms_drv.h"
 
-void *get_pixel_conversion_function(u32 format);
+pixel_read_t get_pixel_conversion_function(u32 format);
 
 void *get_pixel_write_function(u32 format);
 

-- 
2.43.0