NAME

     spigen — SPI generic I/O device driver

SYNOPSIS

     To compile this driver into the kernel, place the following lines in your kernel configuration file:

           device spi
           device spibus
           device spigen

     Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

           spigen_load="YES"

DESCRIPTION

     The spigen driver provides direct access to a slave device on the SPI bus.  Each instance of a spigen
     device is associated with a single chip-select line on the bus, and all I/O performed through that instance
     is done with that chip-select line asserted.

     SPI data transfers are inherently bi-directional; there are not separate read and write operations.  When
     commands and data are sent to a device, data also comes back from the device, although in some cases the
     data may not be useful (or even documented or predictable for some devices).  Likewise on a read operation,
     whatever data is in the buffer at the start of the operation is sent to (and typically ignored by) the
     device, with each outgoing byte then replaced in the buffer by the corresponding incoming byte.  Thus, all
     buffers passed to the transfer functions are both input and output buffers.

     The spigen driver provides access to the SPI slave device with the following ioctl(2) calls, defined in
     <sys/spigenio.h>:

     SPIGENIOC_TRANSFER (struct spigen_transfer)
             Transfer a command and optional associated data to/from the device, using the buffers described by
             the st_command and st_data fields in the spigen_transfer.  Set st_data.iov_len to zero if there is
             no data associated with the command.

             struct spigen_transfer {
                     struct iovec st_command;
                     struct iovec st_data;
             };

     SPIGENIOC_TRANSFER_MMAPPED (spigen_transfer_mmapped)
             Transfer a command and optional associated data to/from the device.  The buffers for the transfer
             are a previously-mmap'd region.  The length of the command and data within that region are
             described by the stm_command_length and stm_data_length fields of spigen_transfer_mmapped.  If
             stm_data_length is non-zero, the data appears in the memory region immediately following the
             command (that is, at offset stm_command_length from the start of the mapped region).

             struct spigen_transfer_mmapped {
                     size_t stm_command_length;
                     size_t stm_data_length;
             };

     SPIGENIOC_GET_CLOCK_SPEED (uint32_t)
             Get the maximum clock speed (bus frequency in Hertz) to be used when communicating with this slave
             device.

     SPIGENIOC_SET_CLOCK_SPEED (uint32_t)
             Set the maximum clock speed (bus frequency in Hertz) to be used when communicating with this slave
             device.  The setting remains in effect for subsequent transfers; it is not necessary to reset this
             before each transfer.  The actual bus frequency may be lower due to hardware limitiations of the
             SPI bus controller device.

     SPIGENIOC_GET_SPI_MODE (uint32_t)
             Get the SPI mode (clock polarity and phase) to be used when communicating with this device.

     SPIGENIOC_SET_SPI_MODE (uint32_t)
             Set the SPI mode (clock polarity and phase) to be used when communicating with this device.  The
             setting remains in effect for subsequent transfers; it is not necessary to reset this before each
             transfer.

HINTS CONFIGURATION

     On a device.hints(5) based system, such as MIPS, these values are configurable for spigen:

     hint.spigen.%d.at
             The spibus the spigen instance is attached to.

     hint.spigen.%d.clock
             The maximum bus frequency to use when communicating with this device.  Actual bus speed may be
             lower, depending on the capabilities of the SPI bus controller hardware.

     hint.spigen.%d.cs
             The chip-select number to assert when performing I/O for this device.  Set the high bit (1 << 31)
             to invert the logic level of the chip select line.

     hint.spigen.%d.mode
             The SPI mode (0-3) to use when communicating with this device.

FDT CONFIGURATION

     On an fdt(4) based system, the spigen device is defined as a slave device subnode of the SPI bus controller
     node.  All properties documented in the spibus.txt bindings document can be used with the spigen device.
     The most commonly-used ones are documented below.

     The following properties are required in the spigen device subnode:

     compatible
             Must be the string "freebsd,spigen".

     reg     Chip select address of device.

     spi-max-frequency
             The maximum bus frequency to use when communicating with this slave device.  Actual bus speed may
             be lower, depending on the capabilities of the SPI bus controller hardware.

     The following properties are optional for the spigen device subnode:

     spi-cpha
             Empty property indicating the slave device requires shifted clock phase (CPHA) mode.

     spi-cpol
             Empty property indicating the slave device requires inverse clock polarity (CPOL) mode.

     spi-cs-high
             Empty property indicating the slave device requires chip select active high.

FILES

     /dev/spigen*

SEE ALSO

     fdt(4), device.hints(5)

HISTORY

     The spigen driver appeared in FreeBSD 11.0.  FDT support appeared in FreeBSD 11.2.