stuff for M1 i2c

i2c-rw.m

// clang -Wall -fmodules -framework Foundation i2c-rw.m -o ./i2c-rw && sudo ./i2c-rw 

@import Darwin;
@import Foundation;
@import IOKit;

typedef CFTypeRef IOAVServiceRef;
extern IOAVServiceRef IOAVServiceCreate(CFAllocatorRef allocator);
extern IOReturn IOAVServiceReadI2C(IOAVServiceRef service, uint32_t chipAddress,
                                   uint32_t offset, void *outputBuffer,
                                   uint32_t outputBufferSize);
extern IOReturn IOAVServiceWriteI2C(IOAVServiceRef service,
                                    uint32_t chipAddress, uint32_t dataAddress,
                                    void *inputBuffer,
                                    uint32_t inputBufferSize);

#define BRIGHTNESS 0x10
#define CONTRAST 0x12
#define AUDIO_SPEAKER_VOLUME 0x62
#define AUDIO_MUTE 0x8D
#define RW_SIZE 10

int main(int argc, char **argv) {
  IOAVServiceRef avService = IOAVServiceCreate(kCFAllocatorDefault);
  if (!avService) {
    NSLog(@"Can't open IOAVService: do you have an external monitor? Are you "
          @"root?");
    return 1;
  }

  UInt8 data[RW_SIZE];
  NSData *nsdata;
  IOReturn err;

  memset(data, 0, sizeof(data));
  err = IOAVServiceReadI2C(avService, 0x37, 0x0, data, sizeof(data));
  if (err) {
    NSLog(@"Nope first i2c: %s", mach_error_string(err));
    return 1;
  }
  nsdata = [NSData dataWithBytes:(const void *)data
                          length:(NSUInteger)sizeof(data)];
  NSLog(@"First read from i2c: %@", nsdata);

  usleep(30000);

  data[0] = 0x51;
  data[1] = 0x82;
  data[2] = 0x01;
  data[3] = BRIGHTNESS;
  data[4] = 0x6e ^ data[0] ^ data[1] ^ data[2] ^ data[3];

  uint32_t len = 5;

  err = IOAVServiceWriteI2C(avService, 0x37, 0x1, data, len);
  if (err) {
    NSLog(@"Nope i2c: %s", mach_error_string(err));
    return 1;
  }
  nsdata = [NSData dataWithBytes:(const void *)data length:(NSUInteger)len];
  NSLog(@"Written to i2c: %@", nsdata);

  usleep(30000);

  memset(data, 0, sizeof(data));
  err = IOAVServiceReadI2C(avService, 0x37, 0x0, data, sizeof(data));
  if (err) {
    NSLog(@"Nope first i2c: %s", mach_error_string(err));
    return 1;
  }
  nsdata = [NSData dataWithBytes:(const void *)data
                          length:(NSUInteger)sizeof(data)];
  NSLog(@"Second read from i2c: %@", nsdata);

  return 0;
}