Dual Head fbdev SDL hack

dualheadsdl.c

// Access both /dev/fb0 and /dev/fb1 with SDL
// Uses dlmopen to load a separate libSDL in another dynamic loader namespace
#define _GNU_SOURCE
#include <dlfcn.h>
#include <SDL/SDL.h>

typedef int (*SDL_Init_t)(Uint32);
typedef SDL_Surface *(*SDL_SetVideoMode_t)(int, int, int, Uint32);
typedef int (*SDL_Flip_t)(SDL_Surface *);
typedef void (*SDL_Quit_t)(void);
typedef int (*putenv_t)(char *);
typedef char *(*SDL_GetError_t)(void);
typedef int (*SDL_ShowCursor_t)(int);

#define WIDTH 640
#define HEIGHT 480

int setup_sdl(SDL_Init_t SDL_Init, SDL_SetVideoMode_t SDL_SetVideoMode, SDL_Flip_t SDL_Flip,
	SDL_GetError_t SDL_GetError, SDL_ShowCursor_t SDL_ShowCursor) {
	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_NOPARACHUTE) < 0) {
		printf("SDL_Init: %s\n", SDL_GetError());
		return 1;
	}

	SDL_Surface *scr = SDL_SetVideoMode(WIDTH, HEIGHT, 32 ,0);
	if (!scr) {
		printf("SDL_SetVideoMode: %s\n", SDL_GetError());
		return 1;
	}
	SDL_ShowCursor(0);
	
	Uint32 *frameBuffer = (Uint32*) scr->pixels;
	int pitch = scr->pitch / sizeof(Uint32);
	
	// show a red/green gradient
	for (int y = 0; y < HEIGHT; y++)
		for (int x = 0; x < WIDTH; x++)
			frameBuffer[y * pitch + x] = ((x * 255 / WIDTH) << 16) | ((y * 255 / HEIGHT) << 8);

	SDL_Flip(scr);

	return 0;
}


int main(int argc, char **argv) {
	void *sdl = dlmopen(LM_ID_NEWLM, "libSDL.so", RTLD_LAZY);
	if (!sdl) {
		printf("dlmopen: %s\n", dlerror());
		return 1;
	}
	
	// setup primary SDL
	if (setup_sdl(SDL_Init, SDL_SetVideoMode, SDL_Flip, SDL_GetError, SDL_ShowCursor))
		return 1;

	// setup secondary SDL on /dev/fb1
	putenv_t putenv_fun = dlsym(sdl, "putenv");
	putenv_fun("SDL_FBDEV=/dev/fb1");
	putenv_fun("SDL_NOVT=1"); // needs SDL patch! needed to prevent hang

	if (setup_sdl(dlsym(sdl, "SDL_Init"), dlsym(sdl, "SDL_SetVideoMode"),
		dlsym(sdl, "SDL_Flip"), dlsym(sdl, "SDL_GetError"),
		dlsym(sdl, "SDL_ShowCursor"))) {
		SDL_Quit();
		return 1;
	}

	int done = 0;
	SDL_Event event;
	while (!done) {
		while (SDL_PollEvent(&event)) {
			switch (event.type) {
				case SDL_KEYDOWN:
					done = 1;
					break;
				case SDL_QUIT:
					done = 1;
					break;
			}
		}
		if (!done)
			SDL_Delay(1);
	}

	SDL_Quit_t quit_fun = dlsym(sdl, "SDL_Quit");
	quit_fun();
	
	SDL_Quit();	

	return 0;
}

sdl-novt.patch

diff --git a/src/video/fbcon/SDL_fbevents.c b/src/video/fbcon/SDL_fbevents.c
index 2bb74580..dd8c4337 100644
--- a/src/video/fbcon/SDL_fbevents.c
+++ b/src/video/fbcon/SDL_fbevents.c
@@ -258,7 +258,8 @@ int FB_OpenKeyboard(_THIS)
 		if ( tty0_fd < 0 ) {
 			tty0_fd = dup(0); /* Maybe stdin is a VT? */
 		}
-		ioctl(tty0_fd, VT_OPENQRY, &current_vt);
+		if ( ! SDL_getenv("SDL_NOVT") )
+			ioctl(tty0_fd, VT_OPENQRY, &current_vt);
 		close(tty0_fd);
 		if ( current_vt > 0 ) {
 			for ( i=0; vcs[i] && (keyboard_fd < 0); ++i ) {