sys/dev/drm/linux_i2c.c

   1 /*
   2  * Copyright (c) 2016 François Tigeot
   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 static struct lock i2c_lock;
  31 LOCK_SYSINIT(i2c_lock, &i2c_lock, "i2cl", LK_CANRECURSE);
  32
  33 int
  34 i2c_add_adapter(struct i2c_adapter *adapter)
  35 {
  36         /* Linux registers a unique bus number here */
  37         return 0;
  38 }
  39
  40 void
  41 i2c_del_adapter(struct i2c_adapter *adapter)
  42 {
  43         /* Linux deletes a unique bus number here */
  44 }
  45
  46 /*
  47  * i2c_transfer()
  48  * The original Linux implementation does:
  49  * 1. return -EOPNOTSUPP if adapter->algo->master_xfer is NULL
  50  * 2. try to transfer msgs by calling adapter->algo->master_xfer()
  51  * 3. if it took more ticks than adapter->timeout, fail
  52  * 4. if the transfer failed, retry up to adapter->retries times
  53  * 5. return the result of the last call of adapter->algo->master_xfer()
  54  */
  55 int
  56 i2c_transfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
  57 {
  58         uint64_t start_ticks;
  59         int ret, tries = 0;
  60
  61         if (adapter->algo->master_xfer == NULL)
  62                 return -EOPNOTSUPP;
  63
  64         lockmgr(&i2c_lock, LK_EXCLUSIVE);
  65         start_ticks = ticks;
  66         do {
  67                 ret = adapter->algo->master_xfer(adapter, msgs, num);
  68                 if (ticks > start_ticks + adapter->timeout)
  69                         break;
  70                 if (ret != -EAGAIN)
  71                         break;
  72                 tries++;
  73         } while (tries < adapter->retries);
  74         lockmgr(&i2c_lock, LK_RELEASE);
  75
  76         return ret;
  77 }
  78
  79 static int
  80 bit_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[], int num)
  81 {
  82         /* XXX Linux really does try to transfer some data here */
  83         return 0;
  84 }
  85
  86 static uint32_t
  87 bit_func(struct i2c_adapter *adap)
  88 {
  89         return (I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
  90                 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
  91                 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
  92                 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING);
  93 }
  94
  95 const struct i2c_algorithm i2c_bit_algo = {
  96         .master_xfer    = bit_xfer,
  97         .functionality  = bit_func,
  98 };