sys/dev/drm/linux_i2c.c

   1 /*
   2  * Copyright (c) 2016-2020 François Tigeot <ftigeot@wolfpond.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice unmodified, this list of conditions, and the following
  10  *    disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include <linux/i2c.h>
  28 #include <linux/i2c-algo-bit.h>
  29
  30 #include <linux/slab.h>
  31
  32 static struct lock i2c_lock;
  33 LOCK_SYSINIT(i2c_lock, &i2c_lock, "i2cl", LK_CANRECURSE);
  34
  35 static void i2c_default_lock_bus(struct i2c_adapter *, unsigned int);
  36 static int i2c_default_trylock_bus(struct i2c_adapter *, unsigned int);
  37 static void i2c_default_unlock_bus(struct i2c_adapter *, unsigned int);
  38
  39 static const struct i2c_lock_operations i2c_default_lock_ops = {
  40         .lock_bus =    i2c_default_lock_bus,
  41         .trylock_bus = i2c_default_trylock_bus,
  42         .unlock_bus =  i2c_default_unlock_bus,
  43 };
  44
  45 int
  46 i2c_add_adapter(struct i2c_adapter *adapter)
  47 {
  48         /* Linux registers a unique bus number here */
  49
  50         /* Setup default locking functions */
  51         if (!adapter->lock_ops)
  52                 adapter->lock_ops = &i2c_default_lock_ops;
  53
  54         return 0;
  55 }
  56
  57 void
  58 i2c_del_adapter(struct i2c_adapter *adapter)
  59 {
  60         /* Linux deletes a unique bus number here */
  61 }
  62
  63 int
  64 __i2c_transfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
  65 {
  66         uint64_t start_ticks;
  67         int ret, tries = 0;
  68
  69         start_ticks = ticks;
  70         do {
  71                 ret = adapter->algo->master_xfer(adapter, msgs, num);
  72                 if (ticks > start_ticks + adapter->timeout)
  73                         break;
  74                 if (ret != -EAGAIN)
  75                         break;
  76                 tries++;
  77         } while (tries < adapter->retries);
  78
  79         return ret;
  80 }
  81
  82 /*
  83  * i2c_transfer()
  84  * The original Linux implementation does:
  85  * 1. return -EOPNOTSUPP if adapter->algo->master_xfer is NULL
  86  * 2. try to transfer msgs by calling adapter->algo->master_xfer()
  87  * 3. if it took more ticks than adapter->timeout, fail
  88  * 4. if the transfer failed, retry up to adapter->retries times
  89  * 5. return the result of the last call of adapter->algo->master_xfer()
  90  */
  91 int
  92 i2c_transfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
  93 {
  94         int ret;
  95
  96         if (adapter->algo->master_xfer == NULL)
  97                 return -EOPNOTSUPP;
  98
  99         adapter->lock_ops->lock_bus(adapter, I2C_LOCK_SEGMENT);
 100         ret = __i2c_transfer(adapter, msgs, num);
 101         adapter->lock_ops->unlock_bus(adapter, I2C_LOCK_SEGMENT);
 102
 103         return ret;
 104 }
 105
 106 static int
 107 bit_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[], int num)
 108 {
 109         /* XXX Linux really does try to transfer some data here */
 110         return 0;
 111 }
 112
 113 static uint32_t
 114 bit_func(struct i2c_adapter *adap)
 115 {
 116         return (I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
 117                 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 118                 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 119                 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING);
 120 }
 121
 122 const struct i2c_algorithm i2c_bit_algo = {
 123         .master_xfer    = bit_xfer,
 124         .functionality  = bit_func,
 125 };
 126
 127 int
 128 i2c_bit_add_bus(struct i2c_adapter *adapter)
 129 {
 130         adapter->algo = &i2c_bit_algo;
 131         adapter->retries = 2;
 132
 133         return 0;
 134 }
 135
 136 struct i2c_client *
 137 i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
 138 {
 139         struct i2c_client *client;
 140
 141         client = kzalloc(sizeof(*client), GFP_KERNEL);
 142         if (client == NULL)
 143                 goto done;
 144
 145         client->adapter = adap;
 146
 147         strlcpy(client->name, info->type, sizeof(client->name));
 148         client->addr = info->addr;
 149
 150 done:
 151         return client;
 152 }
 153
 154 /* Default locking functions */
 155
 156 static void
 157 i2c_default_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
 158 {
 159         lockmgr(&i2c_lock, LK_EXCLUSIVE);
 160 }
 161
 162 static int
 163 i2c_default_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
 164 {
 165         return mutex_trylock(&i2c_lock);
 166 }
 167
 168 static void
 169 i2c_default_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
 170 {
 171         lockmgr(&i2c_lock, LK_RELEASE);
 172 }