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/*
* SPI slave handler controlling system state
*
* This SPI slave handler allows remote control of system reboot, power off,
* halt, and suspend.
*
* Copyright (C) 2016-2017 Glider bvba
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote
* system):
*
* # reboot='\x7c\x50'
* # poweroff='\x71\x3f'
* # halt='\x38\x76'
* # suspend='\x1b\x1b'
* # spidev_test -D /dev/spidev2.0 -p $suspend # or $reboot, $poweroff, $halt
*/
#include <linux/completion.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/spi/spi.h>
/*
* The numbers are chosen to display something human-readable on two 7-segment
* displays connected to two 74HC595 shift registers
*/
#define CMD_REBOOT 0x7c50 /* rb */
#define CMD_POWEROFF 0x713f /* OF */
#define CMD_HALT 0x3876 /* HL */
#define CMD_SUSPEND 0x1b1b /* ZZ */
struct spi_slave_system_control_priv {
struct spi_device *spi;
struct completion finished;
struct spi_transfer xfer;
struct spi_message msg;
__be16 cmd;
};
static
int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);
static void spi_slave_system_control_complete(void *arg)
{
struct spi_slave_system_control_priv *priv = arg;
u16 cmd;
int ret;
if (priv->msg.status)
goto terminate;
cmd = be16_to_cpu(priv->cmd);
switch (cmd) {
case CMD_REBOOT:
dev_info(&priv->spi->dev, "Rebooting system...\n");
kernel_restart(NULL);
break;
case CMD_POWEROFF:
dev_info(&priv->spi->dev, "Powering off system...\n");
kernel_power_off();
break;
case CMD_HALT:
dev_info(&priv->spi->dev, "Halting system...\n");
kernel_halt();
break;
case CMD_SUSPEND:
dev_info(&priv->spi->dev, "Suspending system...\n");
pm_suspend(PM_SUSPEND_MEM);
break;
default:
dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd);
break;
}
ret = spi_slave_system_control_submit(priv);
if (ret)
goto terminate;
return;
terminate:
dev_info(&priv->spi->dev, "Terminating\n");
complete(&priv->finished);
}
static
int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv)
{
int ret;
spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);
priv->msg.complete = spi_slave_system_control_complete;
priv->msg.context = priv;
ret = spi_async(priv->spi, &priv->msg);
if (ret)
dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
return ret;
}
static int spi_slave_system_control_probe(struct spi_device *spi)
{
struct spi_slave_system_control_priv *priv;
int ret;
priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->spi = spi;
init_completion(&priv->finished);
priv->xfer.rx_buf = &priv->cmd;
priv->xfer.len = sizeof(priv->cmd);
ret = spi_slave_system_control_submit(priv);
if (ret)
return ret;
spi_set_drvdata(spi, priv);
return 0;
}
static void spi_slave_system_control_remove(struct spi_device *spi)
{
struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi);
spi_target_abort(spi);
wait_for_completion(&priv->finished);
}
static struct spi_driver spi_slave_system_control_driver = {
.driver = {
.name = "spi-slave-system-control",
},
.probe = spi_slave_system_control_probe,
.remove = spi_slave_system_control_remove,
};
module_spi_driver(spi_slave_system_control_driver);
MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
MODULE_DESCRIPTION("SPI slave handler controlling system state");
MODULE_LICENSE("GPL v2");
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