drivers/input/misc/atmel_captouch.c

   1 /*
   2  * Atmel Atmegaxx Capacitive Touch Button Driver
   3  *
   4  * Copyright (C) 2016 Google, inc.
   5  *
   6  * This software is licensed under the terms of the GNU General Public
   7  * License version 2, as published by the Free Software Foundation, and
   8  * may be copied, distributed, and modified under those terms.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 /*
  17  * It's irrelevant that the HW used to develop captouch driver is based
  18  * on Atmega88PA part and uses QtouchADC parts for sensing touch.
  19  * Calling this driver "captouch" is an arbitrary way to distinguish
  20  * the protocol this driver supported by other atmel/qtouch drivers.
  21  *
  22  * Captouch driver supports a newer/different version of the I2C
  23  * registers/commands than the qt1070.c driver.
  24  * Don't let the similarity of the general driver structure fool you.
  25  *
  26  * For raw i2c access from userspace, use i2cset/i2cget
  27  * to poke at /dev/i2c-N devices.
  28  */
  29
  30 #include <linux/device.h>
  31 #include <linux/kernel.h>
  32 #include <linux/module.h>
  33 #include <linux/init.h>
  34 #include <linux/i2c.h>
  35 #include <linux/input.h>
  36 #include <linux/interrupt.h>
  37 #include <linux/slab.h>
  38
  39 /* Maximum number of buttons supported */
  40 #define MAX_NUM_OF_BUTTONS              8
  41
  42 /* Registers */
  43 #define REG_KEY1_THRESHOLD              0x02
  44 #define REG_KEY2_THRESHOLD              0x03
  45 #define REG_KEY3_THRESHOLD              0x04
  46 #define REG_KEY4_THRESHOLD              0x05
  47
  48 #define REG_KEY1_REF_H                  0x20
  49 #define REG_KEY1_REF_L                  0x21
  50 #define REG_KEY2_REF_H                  0x22
  51 #define REG_KEY2_REF_L                  0x23
  52 #define REG_KEY3_REF_H                  0x24
  53 #define REG_KEY3_REF_L                  0x25
  54 #define REG_KEY4_REF_H                  0x26
  55 #define REG_KEY4_REF_L                  0x27
  56
  57 #define REG_KEY1_DLT_H                  0x30
  58 #define REG_KEY1_DLT_L                  0x31
  59 #define REG_KEY2_DLT_H                  0x32
  60 #define REG_KEY2_DLT_L                  0x33
  61 #define REG_KEY3_DLT_H                  0x34
  62 #define REG_KEY3_DLT_L                  0x35
  63 #define REG_KEY4_DLT_H                  0x36
  64 #define REG_KEY4_DLT_L                  0x37
  65
  66 #define REG_KEY_STATE                   0x3C
  67
  68 /*
  69  * @i2c_client: I2C slave device client pointer
  70  * @input: Input device pointer
  71  * @num_btn: Number of buttons
  72  * @keycodes: map of button# to KeyCode
  73  * @prev_btn: Previous key state to detect button "press" or "release"
  74  * @xfer_buf: I2C transfer buffer
  75  */
  76 struct atmel_captouch_device {
  77         struct i2c_client *client;
  78         struct input_dev *input;
  79         u32 num_btn;
  80         u32 keycodes[MAX_NUM_OF_BUTTONS];
  81         u8 prev_btn;
  82         u8 xfer_buf[8] ____cacheline_aligned;
  83 };
  84
  85 /*
  86  * Read from I2C slave device
  87  * The protocol is that the client has to provide both the register address
  88  * and the length, and while reading back the device would prepend the data
  89  * with address and length for verification.
  90  */
  91 static int atmel_read(struct atmel_captouch_device *capdev,
  92                          u8 reg, u8 *data, size_t len)
  93 {
  94         struct i2c_client *client = capdev->client;
  95         struct device *dev = &client->dev;
  96         struct i2c_msg msg[2];
  97         int err;
  98
  99         if (len > sizeof(capdev->xfer_buf) - 2)
 100                 return -EINVAL;
 101
 102         capdev->xfer_buf[0] = reg;
 103         capdev->xfer_buf[1] = len;
 104
 105         msg[0].addr = client->addr;
 106         msg[0].flags = 0;
 107         msg[0].buf = capdev->xfer_buf;
 108         msg[0].len = 2;
 109
 110         msg[1].addr = client->addr;
 111         msg[1].flags = I2C_M_RD;
 112         msg[1].buf = capdev->xfer_buf;
 113         msg[1].len = len + 2;
 114
 115         err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
 116         if (err != ARRAY_SIZE(msg))
 117                 return err < 0 ? err : -EIO;
 118
 119         if (capdev->xfer_buf[0] != reg) {
 120                 dev_err(dev,
 121                         "I2C read error: register address does not match (%#02x vs %02x)\n",
 122                         capdev->xfer_buf[0], reg);
 123                 return -ECOMM;
 124         }
 125
 126         memcpy(data, &capdev->xfer_buf[2], len);
 127
 128         return 0;
 129 }
 130
 131 /*
 132  * Handle interrupt and report the key changes to the input system.
 133  * Multi-touch can be supported; however, it really depends on whether
 134  * the device can multi-touch.
 135  */
 136 static irqreturn_t atmel_captouch_isr(int irq, void *data)
 137 {
 138         struct atmel_captouch_device *capdev = data;
 139         struct device *dev = &capdev->client->dev;
 140         int error;
 141         int i;
 142         u8 new_btn;
 143         u8 changed_btn;
 144
 145         error = atmel_read(capdev, REG_KEY_STATE, &new_btn, 1);
 146         if (error) {
 147                 dev_err(dev, "failed to read button state: %d\n", error);
 148                 goto out;
 149         }
 150
 151         dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
 152
 153         changed_btn = new_btn ^ capdev->prev_btn;
 154         capdev->prev_btn = new_btn;
 155
 156         for (i = 0; i < capdev->num_btn; i++) {
 157                 if (changed_btn & BIT(i))
 158                         input_report_key(capdev->input,
 159                                          capdev->keycodes[i],
 160                                          new_btn & BIT(i));
 161         }
 162
 163         input_sync(capdev->input);
 164
 165 out:
 166         return IRQ_HANDLED;
 167 }
 168
 169 /*
 170  * Probe function to setup the device, input system and interrupt
 171  */
 172 static int atmel_captouch_probe(struct i2c_client *client,
 173                 const struct i2c_device_id *id)
 174 {
 175         struct atmel_captouch_device *capdev;
 176         struct device *dev = &client->dev;
 177         struct device_node *node;
 178         int i;
 179         int err;
 180
 181         if (!i2c_check_functionality(client->adapter,
 182                                      I2C_FUNC_SMBUS_BYTE_DATA |
 183                                         I2C_FUNC_SMBUS_WORD_DATA |
 184                                         I2C_FUNC_SMBUS_I2C_BLOCK)) {
 185                 dev_err(dev, "needed i2c functionality is not supported\n");
 186                 return -EINVAL;
 187         }
 188
 189         capdev = devm_kzalloc(dev, sizeof(*capdev), GFP_KERNEL);
 190         if (!capdev)
 191                 return -ENOMEM;
 192
 193         capdev->client = client;
 194
 195         err = atmel_read(capdev, REG_KEY_STATE,
 196                             &capdev->prev_btn, sizeof(capdev->prev_btn));
 197         if (err) {
 198                 dev_err(dev, "failed to read initial button state: %d\n", err);
 199                 return err;
 200         }
 201
 202         capdev->input = devm_input_allocate_device(dev);
 203         if (!capdev->input) {
 204                 dev_err(dev, "failed to allocate input device\n");
 205                 return -ENOMEM;
 206         }
 207
 208         capdev->input->id.bustype = BUS_I2C;
 209         capdev->input->id.product = 0x880A;
 210         capdev->input->id.version = 0;
 211         capdev->input->name = "ATMegaXX Capacitive Button Controller";
 212         __set_bit(EV_KEY, capdev->input->evbit);
 213
 214         node = dev->of_node;
 215         if (!node) {
 216                 dev_err(dev, "failed to find matching node in device tree\n");
 217                 return -EINVAL;
 218         }
 219
 220         if (of_property_read_bool(node, "autorepeat"))
 221                 __set_bit(EV_REP, capdev->input->evbit);
 222
 223         capdev->num_btn = of_property_count_u32_elems(node, "linux,keymap");
 224         if (capdev->num_btn > MAX_NUM_OF_BUTTONS)
 225                 capdev->num_btn = MAX_NUM_OF_BUTTONS;
 226
 227         err = of_property_read_u32_array(node, "linux,keycodes",
 228                                          capdev->keycodes,
 229                                          capdev->num_btn);
 230         if (err) {
 231                 dev_err(dev,
 232                         "failed to read linux,keycode property: %d\n", err);
 233                 return err;
 234         }
 235
 236         for (i = 0; i < capdev->num_btn; i++)
 237                 __set_bit(capdev->keycodes[i], capdev->input->keybit);
 238
 239         capdev->input->keycode = capdev->keycodes;
 240         capdev->input->keycodesize = sizeof(capdev->keycodes[0]);
 241         capdev->input->keycodemax = capdev->num_btn;
 242
 243         err = input_register_device(capdev->input);
 244         if (err)
 245                 return err;
 246
 247         err = devm_request_threaded_irq(dev, client->irq,
 248                                         NULL, atmel_captouch_isr,
 249                                         IRQF_ONESHOT,
 250                                         "atmel_captouch", capdev);
 251         if (err) {
 252                 dev_err(dev, "failed to request irq %d: %d\n",
 253                         client->irq, err);
 254                 return err;
 255         }
 256
 257         return 0;
 258 }
 259
 260 #ifdef CONFIG_OF
 261 static const struct of_device_id atmel_captouch_of_id[] = {
 262         {
 263                 .compatible = "atmel,captouch",
 264         },
 265         { /* sentinel */ }
 266 };
 267 MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
 268 #endif
 269
 270 static const struct i2c_device_id atmel_captouch_id[] = {
 271         { "atmel_captouch", 0 },
 272         { }
 273 };
 274 MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
 275
 276 static struct i2c_driver atmel_captouch_driver = {
 277         .probe          = atmel_captouch_probe,
 278         .id_table       = atmel_captouch_id,
 279         .driver         = {
 280                 .name   = "atmel_captouch",
 281                 .of_match_table = of_match_ptr(atmel_captouch_of_id),
 282         },
 283 };
 284 module_i2c_driver(atmel_captouch_driver);
 285
 286 /* Module information */
 287 MODULE_AUTHOR("Hung-yu Wu <hywu@google.com>");
 288 MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
 289 MODULE_LICENSE("GPL v2");