/* * 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 int spi_slave_system_control_remove(struct spi_device *spi) { struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi); spi_slave_abort(spi); wait_for_completion(&priv->finished); return 0; } 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");