drivers/base/regmap/regmap-sccb.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Register map access API - SCCB support
   3
   4 #include <linux/i2c.h>
   5 #include <linux/module.h>
   6 #include <linux/regmap.h>
   7
   8 #include "internal.h"
   9
  10 /**
  11  * sccb_is_available - Check if the adapter supports SCCB protocol
  12  * @adap: I2C adapter
  13  *
  14  * Return true if the I2C adapter is capable of using SCCB helper functions,
  15  * false otherwise.
  16  */
  17 static bool sccb_is_available(struct i2c_adapter *adap)
  18 {
  19         u32 needed_funcs = I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_WRITE_BYTE_DATA;
  20
  21         /*
  22          * If we ever want support for hardware doing SCCB natively, we will
  23          * introduce a sccb_xfer() callback to struct i2c_algorithm and check
  24          * for it here.
  25          */
  26
  27         return (i2c_get_functionality(adap) & needed_funcs) == needed_funcs;
  28 }
  29
  30 /**
  31  * regmap_sccb_read - Read data from SCCB slave device
  32  * @context: Device that will be interacted with
  33  * @reg: Register to be read from
  34  * @val: Pointer to store read value
  35  *
  36  * This executes the 2-phase write transmission cycle that is followed by a
  37  * 2-phase read transmission cycle, returning negative errno else zero on
  38  * success.
  39  */
  40 static int regmap_sccb_read(void *context, unsigned int reg, unsigned int *val)
  41 {
  42         struct device *dev = context;
  43         struct i2c_client *i2c = to_i2c_client(dev);
  44         int ret;
  45         union i2c_smbus_data data;
  46
  47         i2c_lock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
  48
  49         ret = __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags,
  50                                I2C_SMBUS_WRITE, reg, I2C_SMBUS_BYTE, NULL);
  51         if (ret < 0)
  52                 goto out;
  53
  54         ret = __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags,
  55                                I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data);
  56         if (ret < 0)
  57                 goto out;
  58
  59         *val = data.byte;
  60 out:
  61         i2c_unlock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
  62
  63         return ret;
  64 }
  65
  66 /**
  67  * regmap_sccb_write - Write data to SCCB slave device
  68  * @context: Device that will be interacted with
  69  * @reg: Register to write to
  70  * @val: Value to be written
  71  *
  72  * This executes the SCCB 3-phase write transmission cycle, returning negative
  73  * errno else zero on success.
  74  */
  75 static int regmap_sccb_write(void *context, unsigned int reg, unsigned int val)
  76 {
  77         struct device *dev = context;
  78         struct i2c_client *i2c = to_i2c_client(dev);
  79
  80         return i2c_smbus_write_byte_data(i2c, reg, val);
  81 }
  82
  83 static struct regmap_bus regmap_sccb_bus = {
  84         .reg_write = regmap_sccb_write,
  85         .reg_read = regmap_sccb_read,
  86 };
  87
  88 static const struct regmap_bus *regmap_get_sccb_bus(struct i2c_client *i2c,
  89                                         const struct regmap_config *config)
  90 {
  91         if (config->val_bits == 8 && config->reg_bits == 8 &&
  92                         sccb_is_available(i2c->adapter))
  93                 return &regmap_sccb_bus;
  94
  95         return ERR_PTR(-ENOTSUPP);
  96 }
  97
  98 struct regmap *__regmap_init_sccb(struct i2c_client *i2c,
  99                                   const struct regmap_config *config,
 100                                   struct lock_class_key *lock_key,
 101                                   const char *lock_name)
 102 {
 103         const struct regmap_bus *bus = regmap_get_sccb_bus(i2c, config);
 104
 105         if (IS_ERR(bus))
 106                 return ERR_CAST(bus);
 107
 108         return __regmap_init(&i2c->dev, bus, &i2c->dev, config,
 109                              lock_key, lock_name);
 110 }
 111 EXPORT_SYMBOL_GPL(__regmap_init_sccb);
 112
 113 struct regmap *__devm_regmap_init_sccb(struct i2c_client *i2c,
 114                                        const struct regmap_config *config,
 115                                        struct lock_class_key *lock_key,
 116                                        const char *lock_name)
 117 {
 118         const struct regmap_bus *bus = regmap_get_sccb_bus(i2c, config);
 119
 120         if (IS_ERR(bus))
 121                 return ERR_CAST(bus);
 122
 123         return __devm_regmap_init(&i2c->dev, bus, &i2c->dev, config,
 124                                   lock_key, lock_name);
 125 }
 126 EXPORT_SYMBOL_GPL(__devm_regmap_init_sccb);
 127
 128 MODULE_LICENSE("GPL v2");