Daisy Chaining two AD1938 codecs - ALSA System on Chip driver

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().

For more information see: Documentation/spi/spi-summary

You need to set the modalias of your SPI info according to your codec. Valid values are “ad1935” and “ad1937”, You'll also have to adjust bus_num and chip_select according to your board setup.

static struct spi_board_info board_spi_board_info[] __initdata = {     [--snip--]     {          .modalias = "ad1936",          .max_speed_hz = 3125000,     /* max spi clock (SCK) speed in HZ */          .bus_num = 0,          .chip_select = 4, /* CS, change it for your board */          .mode = SPI_MODE_3,     },     [--snip--]};

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().

For more information see: Documentation/spi/spi-summary

You need to set the modalias of your SPI info according to your codec. Valid values are “ad1935” and “ad1937”, You'll also have to adjust bus_num and chip_select according to your board setup.

static struct spi_board_info board_spi_board_info[] __initdata = {     [--snip--]     {          .modalias = "ad1936",          .max_speed_hz = 3125000,     /* max spi clock (SCK) speed in HZ */          .bus_num = 0,          .chip_select = 4, /* CS, change it for your board */          .mode = SPI_MODE_3,     },     [--snip--]};