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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) IBM Corporation 2020
4 */
5
6#include <linux/i2c.h>
7#include <linux/init.h>
8#include <linux/input.h>
9#include <linux/kernel.h>
10#include <linux/limits.h>
11#include <linux/module.h>
12#include <linux/of.h>
13#include <linux/spinlock.h>
14
15#define DEVICE_NAME "ibm-panel"
16#define PANEL_KEYCODES_COUNT 3
17
18struct ibm_panel {
19 u8 idx;
20 u8 command[11];
21 u32 keycodes[PANEL_KEYCODES_COUNT];
22 spinlock_t lock; /* protects writes to idx and command */
23 struct input_dev *input;
24};
25
26static u8 ibm_panel_calculate_checksum(struct ibm_panel *panel)
27{
28 u8 chksum;
29 u16 sum = 0;
30 unsigned int i;
31
32 for (i = 0; i < sizeof(panel->command) - 1; ++i) {
33 sum += panel->command[i];
34 if (sum & 0xff00) {
35 sum &= 0xff;
36 sum++;
37 }
38 }
39
40 chksum = sum & 0xff;
41 chksum = ~chksum;
42 chksum++;
43
44 return chksum;
45}
46
47static void ibm_panel_process_command(struct ibm_panel *panel)
48{
49 u8 button;
50 u8 chksum;
51
52 if (panel->command[0] != 0xff && panel->command[1] != 0xf0) {
53 dev_dbg(&panel->input->dev, "command invalid: %02x %02x\n",
54 panel->command[0], panel->command[1]);
55 return;
56 }
57
58 chksum = ibm_panel_calculate_checksum(panel);
59 if (chksum != panel->command[sizeof(panel->command) - 1]) {
60 dev_dbg(&panel->input->dev,
61 "command failed checksum: %u != %u\n", chksum,
62 panel->command[sizeof(panel->command) - 1]);
63 return;
64 }
65
66 button = panel->command[2] & 0xf;
67 if (button < PANEL_KEYCODES_COUNT) {
68 input_report_key(panel->input, panel->keycodes[button],
69 !(panel->command[2] & 0x80));
70 input_sync(panel->input);
71 } else {
72 dev_dbg(&panel->input->dev, "unknown button %u\n",
73 button);
74 }
75}
76
77static int ibm_panel_i2c_slave_cb(struct i2c_client *client,
78 enum i2c_slave_event event, u8 *val)
79{
80 struct ibm_panel *panel = i2c_get_clientdata(client);
81
82 dev_dbg(&panel->input->dev, "event: %u data: %02x\n", event, *val);
83
84 guard(spinlock_irqsave)(&panel->lock);
85
86 switch (event) {
87 case I2C_SLAVE_STOP:
88 if (panel->idx == sizeof(panel->command))
89 ibm_panel_process_command(panel);
90 else
91 dev_dbg(&panel->input->dev,
92 "command incorrect size %u\n", panel->idx);
93 fallthrough;
94 case I2C_SLAVE_WRITE_REQUESTED:
95 panel->idx = 0;
96 break;
97 case I2C_SLAVE_WRITE_RECEIVED:
98 if (panel->idx < sizeof(panel->command))
99 panel->command[panel->idx++] = *val;
100 else
101 /*
102 * The command is too long and therefore invalid, so set the index
103 * to it's largest possible value. When a STOP is finally received,
104 * the command will be rejected upon processing.
105 */
106 panel->idx = U8_MAX;
107 break;
108 case I2C_SLAVE_READ_REQUESTED:
109 case I2C_SLAVE_READ_PROCESSED:
110 *val = 0xff;
111 break;
112 default:
113 break;
114 }
115
116 return 0;
117}
118
119static int ibm_panel_probe(struct i2c_client *client)
120{
121 struct ibm_panel *panel;
122 int i;
123 int error;
124
125 panel = devm_kzalloc(&client->dev, sizeof(*panel), GFP_KERNEL);
126 if (!panel)
127 return -ENOMEM;
128
129 spin_lock_init(&panel->lock);
130
131 panel->input = devm_input_allocate_device(&client->dev);
132 if (!panel->input)
133 return -ENOMEM;
134
135 panel->input->name = client->name;
136 panel->input->id.bustype = BUS_I2C;
137
138 error = device_property_read_u32_array(&client->dev,
139 "linux,keycodes",
140 panel->keycodes,
141 PANEL_KEYCODES_COUNT);
142 if (error) {
143 /*
144 * Use gamepad buttons as defaults for compatibility with
145 * existing applications.
146 */
147 panel->keycodes[0] = BTN_NORTH;
148 panel->keycodes[1] = BTN_SOUTH;
149 panel->keycodes[2] = BTN_SELECT;
150 }
151
152 for (i = 0; i < PANEL_KEYCODES_COUNT; ++i)
153 input_set_capability(panel->input, EV_KEY, panel->keycodes[i]);
154
155 error = input_register_device(panel->input);
156 if (error) {
157 dev_err(&client->dev,
158 "Failed to register input device: %d\n", error);
159 return error;
160 }
161
162 i2c_set_clientdata(client, panel);
163 error = i2c_slave_register(client, ibm_panel_i2c_slave_cb);
164 if (error) {
165 dev_err(&client->dev,
166 "Failed to register as i2c slave: %d\n", error);
167 return error;
168 }
169
170 return 0;
171}
172
173static void ibm_panel_remove(struct i2c_client *client)
174{
175 i2c_slave_unregister(client);
176}
177
178static const struct of_device_id ibm_panel_match[] = {
179 { .compatible = "ibm,op-panel" },
180 { }
181};
182MODULE_DEVICE_TABLE(of, ibm_panel_match);
183
184static struct i2c_driver ibm_panel_driver = {
185 .driver = {
186 .name = DEVICE_NAME,
187 .of_match_table = ibm_panel_match,
188 },
189 .probe = ibm_panel_probe,
190 .remove = ibm_panel_remove,
191};
192module_i2c_driver(ibm_panel_driver);
193
194MODULE_AUTHOR("Eddie James <[email protected]>");
195MODULE_DESCRIPTION("IBM Operation Panel Driver");
196MODULE_LICENSE("GPL");