I'm trying to configure a SAA6752HS chip (a MPEG-2 encoder) through I2C bus using a Raspberry Pi as a development kit. It was a piece of cake until I had to write at the address 0xC2 of the chip. For this task, I have to use an I2C command that expects a payload of size 189 bytes. So then I stumbled upon a 32 bytes limitation inside the I2C driver, defined by I2C_SMBUS_BLOCK_MAX, in /usr/include/linux/i2c.h. It is not possible to force different values of max limit. Everything around I2C lib end up into the function i2c_smbus_access and any request with more then 32 bytes makes ioctl returns -1. I have no idea how to debug it so far.
static inline __s32 i2c_smbus_access(int file, char read_write, __u8 command,
int size, union i2c_smbus_data *data)
{
struct i2c_smbus_ioctl_data args;
args.read_write = read_write;
args.command = command;
args.size = size;
args.data = data;
return ioctl(file,I2C_SMBUS,&args);
}
I can't understand why there is such limitation, considering that there are devices that require more than 32 bytes of payload data to work (SAA6752HS is such an example).
Are there a way to overcome such limitation without rewrite a new driver?
Thank you in advance.