backlight control on NV chips

[Guido Guenther <agx@debian.org>]

Hi,
I'm attaching a qick hack that I'm using to control the display
brightness on my NV17 based pbook. Simply pass the brightness (1-15) as
argument on the comman line. This is quiet usefull when using offb since
adjusting the brighness only works with rivafb.
Cheers,
 -- Guido

/* 
 * nvbrightness: set brightness on NV based pbooks 
 * (c) 2004 Guido Guenther <agx@sigxcpu.org> 
 */

#include <asm/types.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/fcntl.h>
#include <stdlib.h>

typedef int Bool;
typedef unsigned int U032;

#define CRTC0_BASE (0x91000000 + 0x00600000)
#define BACKLIGHT 0x81C

#define PMC_BASE 0x91000000
#define REG_BASE (PMC_BASE + 0x1000)
#define BRIGHT_OFF 0xF0

volatile U032* regbase;
volatile U032* crtc0base;

Bool
NVMapRegs()
{
	int fd;

        if( ! (fd = open("/dev/mem", O_RDWR))) {
		printf("Failed to open /dev/mem\n");
		return 0;
	}
	regbase = (U032*)mmap(0,
			sizeof(4096),PROT_READ | PROT_WRITE, MAP_SHARED,
			fd, (off_t)REG_BASE);
	if ( ! regbase )
		return 0;
	crtc0base = (U032*)mmap(0,
			sizeof(4096),PROT_READ | PROT_WRITE, MAP_SHARED,
			fd, (off_t)CRTC0_BASE);
	if ( ! crtc0base )
		return 0;
	return 1;
}

/* unmap NVRegs */
void
NVUnmapRegs()
{
	munmap((U032*)regbase, sizeof(4096));
	munmap((U032*)crtc0base, sizeof(4096));
}

int main(int argc, char** argv)
{
    	U032 tmp, level;
	if( argc != 2) {
	    	printf("Usage: %s brightness\n",argv[0]);
	    	return 1;
	}
	level = atoi(argv[1]);
	if(!NVMapRegs()) {
		return 1;
	}
	tmp = regbase[BRIGHT_OFF/4] & 0x0000FFFF;
	tmp |= (1 << 31); // backlight bit
	switch(level) {
	    case 15:    tmp |= 0x05340000; break;
	    default:
			tmp |= (341 + (level * 53)) << 16;
	}
 	regbase[BRIGHT_OFF/4] = tmp;
	NVUnmapRegs();
	return 0;
}

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