tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
38struct 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
46static
47int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);
48
49static 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
90terminate:
91 dev_info(&priv->spi->dev, "Terminating\n");
92 complete(&priv->finished);
93}
94
95static
96int 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
112static 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
134static 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
143static 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};
150module_spi_driver(spi_slave_system_control_driver);
151
152MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
153MODULE_DESCRIPTION("SPI slave handler controlling system state");
154MODULE_LICENSE("GPL v2");