drivers/spi/spi-slave-system-control.c

   1 /*
   2  * SPI slave handler controlling system state
   3  *
   4  * This SPI slave handler allows remote control of system reboot, power off,
   5  * halt, and suspend.
   6  *
   7  * Copyright (C) 2016-2017 Glider bvba
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  *
  13  * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote
  14  * system):
  15  *
  16  *   # reboot='\x7c\x50'
  17  *   # poweroff='\x71\x3f'
  18  *   # halt='\x38\x76'
  19  *   # suspend='\x1b\x1b'
  20  *   # spidev_test -D /dev/spidev2.0 -p $suspend # or $reboot, $poweroff, $halt
  21  */
  22
  23 #include <linux/completion.h>
  24 #include <linux/module.h>
  25 #include <linux/reboot.h>
  26 #include <linux/suspend.h>
  27 #include <linux/spi/spi.h>
  28
  29 /*
  30  * The numbers are chosen to display something human-readable on two 7-segment
  31  * displays connected to two 74HC595 shift registers
  32  */
  33 #define CMD_REBOOT      0x7c50  /* rb */
  34 #define CMD_POWEROFF    0x713f  /* OF */
  35 #define CMD_HALT        0x3876  /* HL */
  36 #define CMD_SUSPEND     0x1b1b  /* ZZ */
  37
  38 struct spi_slave_system_control_priv {
  39         struct spi_device *spi;
  40         struct completion finished;
  41         struct spi_transfer xfer;
  42         struct spi_message msg;
  43         __be16 cmd;
  44 };
  45
  46 static
  47 int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);
  48
  49 static void spi_slave_system_control_complete(void *arg)
  50 {
  51         struct spi_slave_system_control_priv *priv = arg;
  52         u16 cmd;
  53         int ret;
  54
  55         if (priv->msg.status)
  56                 goto terminate;
  57
  58         cmd = be16_to_cpu(priv->cmd);
  59         switch (cmd) {
  60         case CMD_REBOOT:
  61                 dev_info(&priv->spi->dev, "Rebooting system...\n");
  62                 kernel_restart(NULL);
  63
  64         case CMD_POWEROFF:
  65                 dev_info(&priv->spi->dev, "Powering off system...\n");
  66                 kernel_power_off();
  67                 break;
  68
  69         case CMD_HALT:
  70                 dev_info(&priv->spi->dev, "Halting system...\n");
  71                 kernel_halt();
  72                 break;
  73
  74         case CMD_SUSPEND:
  75                 dev_info(&priv->spi->dev, "Suspending system...\n");
  76                 pm_suspend(PM_SUSPEND_MEM);
  77                 break;
  78
  79         default:
  80                 dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd);
  81                 break;
  82         }
  83
  84         ret = spi_slave_system_control_submit(priv);
  85         if (ret)
  86                 goto terminate;
  87
  88         return;
  89
  90 terminate:
  91         dev_info(&priv->spi->dev, "Terminating\n");
  92         complete(&priv->finished);
  93 }
  94
  95 static
  96 int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv)
  97 {
  98         int ret;
  99
 100         spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);
 101
 102         priv->msg.complete = spi_slave_system_control_complete;
 103         priv->msg.context = priv;
 104
 105         ret = spi_async(priv->spi, &priv->msg);
 106         if (ret)
 107                 dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
 108
 109         return ret;
 110 }
 111
 112 static int spi_slave_system_control_probe(struct spi_device *spi)
 113 {
 114         struct spi_slave_system_control_priv *priv;
 115         int ret;
 116
 117         priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
 118         if (!priv)
 119                 return -ENOMEM;
 120
 121         priv->spi = spi;
 122         init_completion(&priv->finished);
 123         priv->xfer.rx_buf = &priv->cmd;
 124         priv->xfer.len = sizeof(priv->cmd);
 125
 126         ret = spi_slave_system_control_submit(priv);
 127         if (ret)
 128                 return ret;
 129
 130         spi_set_drvdata(spi, priv);
 131         return 0;
 132 }
 133
 134 static int spi_slave_system_control_remove(struct spi_device *spi)
 135 {
 136         struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi);
 137
 138         spi_slave_abort(spi);
 139         wait_for_completion(&priv->finished);
 140         return 0;
 141 }
 142
 143 static struct spi_driver spi_slave_system_control_driver = {
 144         .driver = {
 145                 .name   = "spi-slave-system-control",
 146         },
 147         .probe          = spi_slave_system_control_probe,
 148         .remove         = spi_slave_system_control_remove,
 149 };
 150 module_spi_driver(spi_slave_system_control_driver);
 151
 152 MODULE_AUTHOR("Geert Uytterhoeven <[email protected]>");
 153 MODULE_DESCRIPTION("SPI slave handler controlling system state");
 154 MODULE_LICENSE("GPL v2");