linux内核中的regmap是如何初始化的?

1. 内核版本

　　5.2.0

2. 请看devm_regmap_init_i2c (include/linux/regmap.h)

/**
 * devm_regmap_init_i2c() - Initialise managed register map
 *
 * @i2c: Device that will be interacted with
 * @config: Configuration for register map
 *
 * The return value will be an ERR_PTR() on error or a valid pointer
 * to a struct regmap.  The regmap will be automatically freed by the
 * device management code.
 */
#define devm_regmap_init_i2c(i2c, config)                               \
        __regmap_lockdep_wrapper(__devm_regmap_init_i2c, #config,       \
                                i2c, config)

3. 看看__regmap_lockdep_wrapper

/*
 * Wrapper for regmap_init macros to include a unique lockdep key and name
 * for each call. No-op if CONFIG_LOCKDEP is not set.
 *
 * @fn: Real function to call (in the form __[*_]regmap_init[_*])
 * @name: Config variable name (#config in the calling macro)
 **/#define __regmap_lockdep_wrapper(fn, name, ...)                         \
(                                                                       \
        ({                                                              \
                static struct lock_class_key _key;                      \
                fn(__VA_ARGS__, &_key,                                  \
                        KBUILD_BASENAME ":"                             \
                        __stringify(__LINE__) ":"                       \
                        "(" name ")->lock");                            \
        })                                                              \
)

4. KBUILD_BASENAME的定义在哪里?

　　在编译时由编译选项-D提供,如此处为:

　　　　-DKBUILD_BASENAME='"regmap_i2c"'

　　

5. 展开

假设__LINE__等于99行,那么

(                                                                       \
        ({                                                              \
                static struct lock_class_key _key;                      \
                __devm_regmap_init_i2c(__VA_ARGS__, &_key,                                  \
                        "regmap_i2c:99:config->lock");                             \
        })                                                              \
)

6. 看看__devm_regmap_init_i2c的执行路径

　　__devm_regmap_init_i2c

　　　　-> regmap_get_i2c_bus

　　　　-> __devm_regmap_init

　　　　　　-> devres_alloc

　　　　　　-> __regmap_init

7. 重点分析__regmap_init

        map->dev = dev;
        map->bus = bus;
        map->bus_context = bus_context;
        map->max_register = config->max_register;
        map->wr_table = config->wr_table;
        map->rd_table = config->rd_table;
        map->volatile_table = config->volatile_table;
        map->precious_table = config->precious_table;
        map->wr_noinc_table = config->wr_noinc_table;
        map->rd_noinc_table = config->rd_noinc_table;
        map->writeable_reg = config->writeable_reg;
        map->readable_reg = config->readable_reg;
        map->volatile_reg = config->volatile_reg;
        map->precious_reg = config->precious_reg;
        map->writeable_noinc_reg = config->writeable_noinc_reg;
        map->readable_noinc_reg = config->readable_noinc_reg;
        map->cache_type = config->cache_type;    

总结:

　　做的主要工作即为填充map结构体