BFPCTRL
ret = mcp251x_write_bits(priv->spi, BFPCTRL, val, val);
mcp251x_write_bits(priv->spi, BFPCTRL, val, 0);
reg = BFPCTRL;
val = mcp251x_read_reg(priv->spi, BFPCTRL);
ret = mcp251x_write_bits(priv->spi, BFPCTRL, mask, val);
ret = mcp251x_write_bits(priv->spi, BFPCTRL, mask, val);
mcp251x_write_reg(spi, BFPCTRL, priv->reg_bfpctrl);