linux/drivers/spi/spi-mux.c

// SPDX-License-Identifier: GPL-2.0
//
// General Purpose SPI multiplexer

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mux/consumer.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>

#define SPI_MUX_NO_CS …

/**
 * DOC: Driver description
 *
 * This driver supports a MUX on an SPI bus. This can be useful when you need
 * more chip selects than the hardware peripherals support, or than are
 * available in a particular board setup.
 *
 * The driver will create an additional SPI controller. Devices added under the
 * mux will be handled as 'chip selects' on this controller.
 */

/**
 * struct spi_mux_priv - the basic spi_mux structure
 * @spi:		pointer to the device struct attached to the parent
 *			spi controller
 * @current_cs:		The current chip select set in the mux
 * @child_msg_complete: The mux replaces the complete callback in the child's
 *			message to its own callback; this field is used by the
 *			driver to store the child's callback during a transfer
 * @child_msg_context:	Used to store the child's context to the callback
 * @child_msg_dev:	Used to store the spi_device pointer to the child
 * @mux:		mux_control structure used to provide chip selects for
 *			downstream spi devices
 */
struct spi_mux_priv { … };

/* should not get called when the parent controller is doing a transfer */
static int spi_mux_select(struct spi_device *spi)
{ … }

static int spi_mux_setup(struct spi_device *spi)
{ … }

static void spi_mux_complete_cb(void *context)
{ … }

static int spi_mux_transfer_one_message(struct spi_controller *ctlr,
						struct spi_message *m)
{ … }

static int spi_mux_probe(struct spi_device *spi)
{ … }

static const struct spi_device_id spi_mux_id[] = …;
MODULE_DEVICE_TABLE(spi, spi_mux_id);

static const struct of_device_id spi_mux_of_match[] = …;
MODULE_DEVICE_TABLE(of, spi_mux_of_match);

static struct spi_driver spi_mux_driver = …;

module_spi_driver(…) …;

MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;