spi bus numbering in board file

Hello,

I would like to ask what is the value that should be inserted in .bus_num , is it the physical bus number + 1 ?

for example is device is connect to bus #1, I should put there  .bus_num = 2 ?

struct spi_board_info __initdata ti8148_spi_slave_info[] = {
{

.modalias = "rtc-rv3049",
.max_speed_hz = 1000000,
.chip_select = 1,
.bus_num = 2,
.mode = SPI_MODE_0
},
{
.modalias = "mb85rs2mt",
.platform_data = &ti8148_spi_flash,
.irq = -1,
.max_speed_hz = 75000000,
.bus_num = 1,
.chip_select = 0,
},

};

Thanks

Ran