struct spi_master(9)
NAME
struct_spi_master - interface to SPI master controller
SYNOPSIS
struct spi_master {
struct device dev;
s16 bus_num;
u16 num_chipselect;
int (* setup) (struct spi_device *spi);
int (* transfer) (struct spi_device *spi,struct spi_message *mesg);
void (* cleanup) (struct spi_device *spi);
};
MEMBERS
- dev
- device interface to this driver
- bus_num
- board-specific (and often SOC-specific) identifier for a given SPI controller.
- num_chipselect
- chipselects are used to distinguish individual SPI slaves, and are numbered from zero to num_chipselects. each slave has a chipselect signal, but itīs common that not every chipselect is connected to a slave.
- setup
- updates the device mode and clocking records used by a deviceīs SPI
controller; protocol code may call this. This must fail if an
unrecognized or unsupported mode is requested. Itīs always safe to call this unless transfers are pending on the device whose settings are being modified. - transfer
- adds a message to the controllerīs transfer queue.
- cleanup
- frees controller-specific state
DESCRIPTION
Each SPI master controller can communicate with one or more spi_device
children. These make a small bus, sharing MOSI, MISO and SCK signals
but not chip select signals. Each device may be configured to use a
different clock rate, since those shared signals are ignored unless the
chip is selected.
The driver for an SPI controller manages access to those devices
through a queue of spi_message transactions, copying data between CPU
memory and an SPI slave device. For each such message it queues, it
calls the messageīs completion function when the transaction completes.