Updated Makefile and document ipukms_csc.

Author: Ahmed Ammar

Makefile

@@ -1,7 +1,6 @@
 CC=$(CROSS_COMPILE)gcc
 
-%.o: %.c
-	$(CC) -O2 -c $^ -o $@
+all:
+	$(CC) -o libvpu_encode libvpu_encode.c -lvpu -lpthread
+	$(CC) -o ipukms_csc ipukms_csc.c -I /usr/include/libpng/  -lpng -ldrm
 
-all: libvpu_encode.o
-	gcc -o libvpu_encode libvpu_encode.o -lvpu -lpthread

ipukms_csc.c

@@ -6,12 +6,14 @@
 #include <drm/imx-ipu-v3-ioctls.h>
 #include <png.h>
 
-
+// default width/height of input files
 #define WIDTH 640
 #define HEIGHT 360
 
+// png creation helper functions
 #include "ipukms_png.c"
 
+// structure to hold DRM framebuffer information
 struct csc_bo {
 	uint32_t handle;
 	uint32_t size;
@@ -21,6 +23,7 @@ struct csc_bo {
 	uint32_t pitch;
 };
 
+// framebuffer creation function
 struct csc_bo *csc_bo_create(int fd,
 			const unsigned width, const unsigned height,
 			const unsigned bpp)
@@ -54,6 +57,7 @@ struct csc_bo *csc_bo_create(int fd,
 	return NULL;
 }
 
+// framebuffer userspace mapping function
 static int csc_bo_map(int fd, struct csc_bo *bo)
 {
 	struct drm_mode_map_dumb arg;
@@ -81,6 +85,7 @@ static int csc_bo_map(int fd, struct csc_bo *bo)
 	return 0;
 }
 
+// framebuffer destruction function
 static int csc_bo_destroy(int fd, struct csc_bo *bo)
 {
 	struct drm_mode_destroy_dumb arg;
@@ -101,38 +106,44 @@ static int csc_bo_destroy(int fd, struct csc_bo *bo)
 	return 0;
 }
 
+// main function
 int main(void)
 {
 	struct csc_bo* input_bo;
 	struct csc_bo* output_bo;
 	int ret, fd;
 
-	if ((fd = drmOpen("imx-drm", NULL)) < 0) {
+	// open DRM device
+	if ((fd = drmOpen("imx-drm", "platform:imx-drm:00")) < 0) {
 		printf("drmOpen failed.\n");
 		return -1;
 	}
 
-	//create buffer for csc in/out
+	// create buffer for csc input
 	input_bo = csc_bo_create(fd, WIDTH, HEIGHT, 32);
 	if (!input_bo) {
 		printf("Couldn't create input gem bo\n");
 		return -1;
 	}
+
+	// map the input buffer
 	if (csc_bo_map(fd, input_bo)) {
 		printf("Couldn't map input bo\n");
 		return -1;
 	}
 
+	// create buffer for csc output
 	output_bo = csc_bo_create(fd, WIDTH, HEIGHT, 32);
 	if (!output_bo) {
 		printf("Couldn't create output gem bo\n");
 		return -1;
 	}
 
+	// create ipu csc request
 	struct drm_imx_ipu_queue req = {
 		.task = IPU_TASK_CSC,
 		.input = {
-			.phys = input_bo->phys, //id of gem_cma object
+			.phys = input_bo->phys,
 			.pix = {
 				.pixelformat = V4L2_PIX_FMT_UYVY,
 				.bytesperline = 2 * WIDTH,
@@ -145,12 +156,10 @@ int main(void)
 			},
 		},
 		.output = {
-			.phys = output_bo->phys, //id of gem_cma object
+			.phys = output_bo->phys,
 			.pix = {
 				.pixelformat = V4L2_PIX_FMT_RGB32,
 				.bytesperline = 4 * WIDTH,
-				//.pixelformat = V4L2_PIX_FMT_YUV420,
-				//.bytesperline = 1 * WIDTH,
 				.width = WIDTH,
 				.height = HEIGHT,
 			},
@@ -159,58 +168,82 @@ int main(void)
 				.height = HEIGHT,
 			},
 		},
-#if 0
-		.csc_coeffs[4][3] = {
-			{149, 0, 0},	/* C00, C01, C02 */
-			{149, 0, 0},	/* C10, C11, C12 */
-			{149, 0, 0},	/* C20, C21, C22 */
-			{0, 0, 0},	/*  A0,  A1,  A2 */
-		},
-#endif
 	};
+
+	// color-space conversion (csc) coefficient matrix values
 	uint32_t *c0, *c1, *c2, *a0;
-	c0 = calloc(3, sizeof(uint32_t));
+
+	/* i.MX6 Reference Manual (Chapter 36: Table 36-18)
+	 * Z0 = X0*C00 + X1*C01 +X2*C02+A0;
+	 * Z1 = X0*C10 + X1*C11 +X2*C12+A1;
+	 * Z2 = X0*C20 + X1*C21 +X2*C22+A2;
+	 *
+	 * Where c0[0] == C00, c0[1] == C01, c0[2] == C02
+	 */
+
+	// allocate csc coefficients for kernel task
+	c0 = calloc(3, sizeof(uint32_t)); 
 	c1 = calloc(3, sizeof(uint32_t));
 	c2 = calloc(3, sizeof(uint32_t));
 	a0 = calloc(3, sizeof(uint32_t));
 
-	printf("%p %p %p %p\n", c0, c1, c2, a0);
-
-	c0[0] = 149;
-	c1[0] = 149;
-	c2[0] = 149;
-
+	// converting grayscale to RGB32 R = G = B = Y (dropping chroma)
+	// Z0 = R = X0 * C00 
+	// Z1 = G = X0 * C10
+	// Z2 = B = X0 * C20 
+	//
+	// C00, C10, C20 = 0.99
+	c0[0] = 255;
+	c1[0] = 255;
+	c2[0] = 255;
+
+	// set coefficients for kernel ioctl request
 	req.csc_coeffs[0] = c0;
 	req.csc_coeffs[1] = c1;
 	req.csc_coeffs[2] = c2;
 	req.csc_coeffs[3] = a0;
 
-	/* Open YUV420P sample file */
+	// open grayscale sample input file
 	FILE *fp = fopen("output.gray", "r");
-	srand(time(NULL));
-	//fseek(fp, WIDTH*HEIGHT*3/2*(rand()%87), 0);
+
+	// another version using a larger sample
+	// FILE *fp = fopen("BigBuckBunny_640x360_small.yuv", "r");
+	// srand(time(NULL));
+	// fseek(fp, WIDTH*HEIGHT*3/2*(rand()%87), 0);
+
+	// read input into input framebuffer
 	fread(input_bo->ptr, 1, WIDTH*HEIGHT*2, fp);
+
+	// close read file
 	fclose(fp);
 
-	//convert to YUV420
+	// convert to input framebuffer RGB32
 	if (drmCommandWriteRead(fd, DRM_IMX_IPU_QUEUE, &req, sizeof(req))) {
 		printf("drmCommandWriteRead failed. [%s]. (%d)\n", strerror(errno), sizeof(req));
 		return -errno;
 	}
 
+	// map the output framebuffer to userspace
 	if (csc_bo_map(fd, output_bo)) {
 		printf("Couldn't map output bo\n");
 		return -1;
 	}
 
-	//let's see it!
+	// let's see it!
+	// save output framebuffer to png (png only supports rgb24)
+
+	// allocate the rgb24 output array
 	char* rgb_matrix = (char*) malloc(WIDTH * HEIGHT * 3);
 	const char * rgb = (const char *)output_bo->ptr;
 
-	//rgba565_to_rgb888(rgb, rgb_matrix, WIDTH*HEIGHT);
+	// convert rgb32 to rgb24 using helper function
 	rgba8888_to_rgb888(rgb, rgb_matrix, WIDTH*HEIGHT);
 
+	// save output png using helper function
 	save_png("output.png", rgb_matrix, WIDTH, HEIGHT);
+
+	// free the allocated rgb24 matrix
 	free(rgb_matrix);
+
 	return 0;
 }