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
18 struct 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
ibm_panel_calculate_checksum(struct ibm_panel * panel)26 static 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
ibm_panel_process_command(struct ibm_panel * panel)47 static 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
ibm_panel_i2c_slave_cb(struct i2c_client * client,enum i2c_slave_event event,u8 * val)77 static int ibm_panel_i2c_slave_cb(struct i2c_client *client,
78 enum i2c_slave_event event, u8 *val)
79 {
80 unsigned long flags;
81 struct ibm_panel *panel = i2c_get_clientdata(client);
82
83 dev_dbg(&panel->input->dev, "event: %u data: %02x\n", event, *val);
84
85 spin_lock_irqsave(&panel->lock, flags);
86
87 switch (event) {
88 case I2C_SLAVE_STOP:
89 if (panel->idx == sizeof(panel->command))
90 ibm_panel_process_command(panel);
91 else
92 dev_dbg(&panel->input->dev,
93 "command incorrect size %u\n", panel->idx);
94 fallthrough;
95 case I2C_SLAVE_WRITE_REQUESTED:
96 panel->idx = 0;
97 break;
98 case I2C_SLAVE_WRITE_RECEIVED:
99 if (panel->idx < sizeof(panel->command))
100 panel->command[panel->idx++] = *val;
101 else
102 /*
103 * The command is too long and therefore invalid, so set the index
104 * to it's largest possible value. When a STOP is finally received,
105 * the command will be rejected upon processing.
106 */
107 panel->idx = U8_MAX;
108 break;
109 case I2C_SLAVE_READ_REQUESTED:
110 case I2C_SLAVE_READ_PROCESSED:
111 *val = 0xff;
112 break;
113 default:
114 break;
115 }
116
117 spin_unlock_irqrestore(&panel->lock, flags);
118
119 return 0;
120 }
121
ibm_panel_probe(struct i2c_client * client)122 static int ibm_panel_probe(struct i2c_client *client)
123 {
124 struct ibm_panel *panel;
125 int i;
126 int error;
127
128 panel = devm_kzalloc(&client->dev, sizeof(*panel), GFP_KERNEL);
129 if (!panel)
130 return -ENOMEM;
131
132 spin_lock_init(&panel->lock);
133
134 panel->input = devm_input_allocate_device(&client->dev);
135 if (!panel->input)
136 return -ENOMEM;
137
138 panel->input->name = client->name;
139 panel->input->id.bustype = BUS_I2C;
140
141 error = device_property_read_u32_array(&client->dev,
142 "linux,keycodes",
143 panel->keycodes,
144 PANEL_KEYCODES_COUNT);
145 if (error) {
146 /*
147 * Use gamepad buttons as defaults for compatibility with
148 * existing applications.
149 */
150 panel->keycodes[0] = BTN_NORTH;
151 panel->keycodes[1] = BTN_SOUTH;
152 panel->keycodes[2] = BTN_SELECT;
153 }
154
155 for (i = 0; i < PANEL_KEYCODES_COUNT; ++i)
156 input_set_capability(panel->input, EV_KEY, panel->keycodes[i]);
157
158 error = input_register_device(panel->input);
159 if (error) {
160 dev_err(&client->dev,
161 "Failed to register input device: %d\n", error);
162 return error;
163 }
164
165 i2c_set_clientdata(client, panel);
166 error = i2c_slave_register(client, ibm_panel_i2c_slave_cb);
167 if (error) {
168 dev_err(&client->dev,
169 "Failed to register as i2c slave: %d\n", error);
170 return error;
171 }
172
173 return 0;
174 }
175
ibm_panel_remove(struct i2c_client * client)176 static void ibm_panel_remove(struct i2c_client *client)
177 {
178 i2c_slave_unregister(client);
179 }
180
181 static const struct of_device_id ibm_panel_match[] = {
182 { .compatible = "ibm,op-panel" },
183 { }
184 };
185 MODULE_DEVICE_TABLE(of, ibm_panel_match);
186
187 static struct i2c_driver ibm_panel_driver = {
188 .driver = {
189 .name = DEVICE_NAME,
190 .of_match_table = ibm_panel_match,
191 },
192 .probe = ibm_panel_probe,
193 .remove = ibm_panel_remove,
194 };
195 module_i2c_driver(ibm_panel_driver);
196
197 MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
198 MODULE_DESCRIPTION("IBM Operation Panel Driver");
199 MODULE_LICENSE("GPL");
200