drivers/input/misc/ibm-panel.c

   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
  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
  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
  77 static 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
 119 static 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
 173 static void ibm_panel_remove(struct i2c_client *client)
 174 {
 175         i2c_slave_unregister(client);
 176 }
 177
 178 static const struct of_device_id ibm_panel_match[] = {
 179         { .compatible = "ibm,op-panel" },
 180         { }
 181 };
 182 MODULE_DEVICE_TABLE(of, ibm_panel_match);
 183
 184 static 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 };
 192 module_i2c_driver(ibm_panel_driver);
 193
 194 MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
 195 MODULE_DESCRIPTION("IBM Operation Panel Driver");
 196 MODULE_LICENSE("GPL");