Linux中的GPIO操作的一些函数：
要使用gpio，首先要使用这个函数来分配一个gpio
int gpio_request(unsigned gpio, const char *label)
指定输入还是输入模式
int gpio_direction_input(unsigned gpio);
这个函数能设置gpio的输出模式为输入
int gpio_direction_output(unsigned gpio, int value)
这个函数能设置gpio的控制寄存器为输出模式，并且输出value(0-低电平 1-高电平)
gpio_set_value则是一个宏，它只负责让指定的gpio输出高低电平，但是不担保gpio的控制器是输出模式
#define gpio_set_value __gpio_set_value
/**
* __gpio_set_value() - assign a gpio's value
* @gpio: gpio whose value will be assigned
* @value: value to assign
* Context: any
*
* This is used directly or indirectly to implement gpio_set_value().
* It invokes the associated gpio_chip.set() method.
*/
void __gpio_set_value(unsigned gpio, int value)
{
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(chip->can_sleep);
trace_gpio_value(gpio, 0, value);
chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);
linux/arch/arm/plat-s3c/include/plat/gpio-cfg.h这个里面给我们提供了很多S3C平台的GPIO操作接口，我们来分析分析
第一部分：关于控制寄存器的设置函数
1.s3c_gpio_cfgpin()设置pin的功能
/** * s3c_gpio_cfgpin() - Change the GPIO function of a pin. * @pin pin The pin number to configure. * @to to The configuration for the pin's function. * * Configure which function is actually connected to the external * pin, such as an gpio input, output or some form of special function * connected to an internal peripheral block. * * The @to parameter can be one of the generic S3C_GPIO_INPUT, S3C_GPIO_OUTPUT * or S3C_GPIO_SFN() to indicate one of the possible values that the helper * will then generate the correct bit mask and shift for the configuration. * * If a bank of GPIOs all needs to be set to special-function 2, then * the following code will work: * * for (gpio = start; gpio < end; gpio++) * s3c_gpio_cfgpin(gpio, S3C_GPIO_SFN(2)); * * The @to parameter can also be a specific value already shifted to the * correct position in the control register, although these are discouraged * in newer kernels and are only being kept for compatibility. */ extern int s3c_gpio_cfgpin(unsigned int pin, unsigned int to);
功能：设置GPIO的一个引脚的功能。
参数：@pin：要设置的引脚号
@to： 要设置成什么功能，有三个选择，如下
/* Defines for generic pin configurations */ #define S3C_GPIO_INPUT (S3C_GPIO_SPECIAL(0)) //设置成输出模式 #define S3C_GPIO_OUTPUT (S3C_GPIO_SPECIAL(1)) //设置成输入模式 #define S3C_GPIO_SFN(x) (S3C_GPIO_SPECIAL(x)) //设置成其他模式，根据参数x决定
其实前两种都可以使用第三种宏来实现，
设置成输出模式：S3C_GPIO_SFN(0)
设置成输入模式：S3C_GPIO_SFN(1)
它还举个例子，如果一组GPIO都需要设置成相同的功能，比如功能2，可以使用下面的代码
for (gpio = start; gpio < end; gpio++) s3c_gpio_cfgpin(gpio, S3C_GPIO_SFN(2));
to这个参数也可以自己用掩码方式实现
#define S3C_GPIO_SPECIAL_MARK (0xfffffff0) #define S3C_GPIO_SPECIAL(x) (S3C_GPIO_SPECIAL_MARK | (x))
可以看到，实际那三个宏也是通过掩码方式实现的，当然我们也可以自己用位移，屏蔽等方法实现，但是因为兼容性的问题，所以不鼓励那样做。
2.s3c_gpio_getcfg()获得pin的设置值
/** * s3c_gpio_getcfg - Read the current function for a GPIO pin * @pin: The pin to read the configuration value for. * * Read the configuration state of the given @pin, returning a value that * could be passed back to s3c_gpio_cfgpin(). * * @sa s3c_gpio_cfgpin */ extern unsigned s3c_gpio_getcfg(unsigned int pin);
功能：读取一个pin的当前功能值
参数：@pin：要读取设置的pin
很好理解，有设置的，就要有读取的，有写就有读。
3.s3c_gpio_cfgin_range()设置一个范围內的引脚设置
/** * s3c_gpio_cfgpin_range() - Change the GPIO function for configuring pin range * @start: The pin number to start at * @nr: The number of pins to configure from @start. * @cfg: The configuration for the pin's function * * Call s3c_gpio_cfgpin() for the @nr pins starting at @start. * * @sa s3c_gpio_cfgpin. */ extern int s3c_gpio_cfgpin_range(unsigned int start, unsigned int nr, unsigned int cfg);
功能：设置一个范围內的所有引脚设置
参数：@start：起始引脚
@nr： 设置的引脚数量,从其实引脚开始，一共要设置几个引脚的数量
@cfg: 要设置的引脚功能
还记得我们刚才那个例子吗，设置一组GPIO的功能，看看实现就知道了，就是那个s3c_gpio_cfgpin的封装
int s3c_gpio_cfgpin_range(unsigned int start, unsigned int nr,
unsigned int cfg)
{
int ret;
for (; nr > 0; nr--, start++) {
ret = s3c_gpio_cfgpin(start, cfg);
if (ret != 0)
return ret;
}
return 0;
}
EXPORT_SYMBOL_GPL(s3c_gpio_cfgpin_range);
第二部分：关于上下拉设置的寄存器设置
下面几个宏上下拉设置寄存器的几个状态值
/* Define values for the pull-{up,down} available for each gpio pin.
*
* These values control the state of the weak pull-{up,down} resistors
* available on most pins on the S3C series. Not all chips support both
* up or down settings, and it may be dependent on the chip that is being
* used to whether the particular mode is available.
*/
#define S3C_GPIO_PULL_NONE ((__force s3c_gpio_pull_t)0x00) //关闭，上拉下拉都关闭
#define S3C_GPIO_PULL_DOWN ((__force s3c_gpio_pull_t)0x01) //下拉
#define S3C_GPIO_PULL_UP ((__force s3c_gpio_pull_t)0x02) //上拉
1.s3c_gpio_setpull()设置GPIO引脚的上下拉使能
/**
* s3c_gpio_setpull() - set the state of a gpio pin pull resistor
* @pin: The pin number to configure the pull resistor.
* @pull: The configuration for the pull resistor.
*
* This function sets the state of the pull-{up,down} resistor for the
* specified pin. It will return 0 if successful, or a negative error
* code if the pin cannot support the requested pull setting.
*
* @pull is one of S3C_GPIO_PULL_NONE, S3C_GPIO_PULL_DOWN or S3C_GPIO_PULL_UP.
*/
extern int s3c_gpio_setpull(unsigned int pin, s3c_gpio_pull_t pull);
功能：设置GPIO引脚的上下拉使能状态
参数：@pin：要设置的引脚
@pull：设置的状态，值就是上面三个宏之一
2.s3c_gpio_getpull()读取指定GPIO的上下拉状态
/** * s3c_gpio_getpull() - get the pull resistor state of a gpio pin * @pin: The pin number to get the settings for * * Read the pull resistor value for the specified pin. */ extern s3c_gpio_pull_t s3c_gpio_getpull(unsigned int pin);
功能：读取指定GPIO的上下拉状态
参数：@pin：要读取的引脚
3.s3c_gpio_cfgall()设置一组GPIO引脚的功能和上下拉状态
/** * s3c_gpio_cfgall_range() - configure range of gpio functtion and pull. * @start: The gpio number to start at. * @nr: The number of gpio to configure from @start. * @cfg: The configuration to use * @pull: The pull setting to use. * * Run s3c_gpio_cfgpin() and s3c_gpio_setpull() over the gpio range starting * @gpio and running for @size. * * @sa s3c_gpio_cfgpin * @sa s3c_gpio_setpull * @sa s3c_gpio_cfgpin_range */ extern int s3c_gpio_cfgall_range(unsigned int start, unsigned int nr, unsigned int cfg, s3c_gpio_pull_t pull);
功能：设置一组GPIO引脚的功能和上下拉状态
参数：@start：要设置的GPIO起始引脚
@nr：要设置的引脚范围，从其实引脚算起
@cfg：要设置成什么功能
@pull：要设置成什么状态(上下拉)
这个应该是s3c_set_cfgpin_range和s3c_gpio_setpull()的混合体，我们看看它的实现
int s3c_gpio_cfgall_range(unsigned int start, unsigned int nr,
unsigned int cfg, s3c_gpio_pull_t pull)
{
int ret;
for (; nr > 0; nr--, start++) {
s3c_gpio_setpull(start, pull);
ret = s3c_gpio_cfgpin(start, cfg);
if (ret != 0)
return ret;
}
return 0;
}
EXPORT_SYMBOL_GPL(s3c_gpio_cfgall_range);
哦，是s3c_gpio_setpull()和s3c_gpio_setpull()的混合体
第三部分：关于驱动能力寄存器
/* Define values for the drvstr available for each gpio pin. * * These values control the value of the output signal driver strength, * configurable on most pins on the S5P series. */ #define S5P_GPIO_DRVSTR_LV1 ((__force s5p_gpio_drvstr_t)0x0) #define S5P_GPIO_DRVSTR_LV2 ((__force s5p_gpio_drvstr_t)0x2) #define S5P_GPIO_DRVSTR_LV3 ((__force s5p_gpio_drvstr_t)0x1) #define S5P_GPIO_DRVSTR_LV4 ((__force s5p_gpio_drvstr_t)0x3)
1.s5p_gpio_get_drvstr设置GPIO引脚的驱动能力寄存器
/** * s3c_gpio_set_drvstr() - set the driver streght value of a gpio pin * @pin: The pin number to configure the driver streght value * @drvstr: The new value of the driver strength * * This function sets the driver strength value for the specified pin. * It will return 0 if successful, or a negative error code if the pin * cannot support the requested setting. */ extern int s5p_gpio_set_drvstr(unsigned int pin, s5p_gpio_drvstr_t drvstr);
功能：设置GPIO引脚的驱动能力寄存器
参数：@pin：要设置的引脚
@drvstr：设置驱动能力的强度，可想而知，它的值就是那四个宏的其中之一
2.s5p_gpio_get_drvstr()读取GPIO引脚的驱动能力寄存器的值
/** * s5c_gpio_get_drvstr() - get the driver streght value of a gpio pin * @pin: The pin number to get the settings for * * Read the driver streght value for the specified pin. */ extern s5p_gpio_drvstr_t s5p_gpio_get_drvstr(unsigned int pin);
功能：读取GPIO引脚的驱动能力寄存器的值
参数：@pin：要读取的GPIO引脚
第四部分：关于掉电模式寄存器
/* Define values for the power down configuration available for each gpio pin. * * These values control the state of the power down configuration resistors * available on most pins on the S5P series. */ #define S5P_GPIO_PD_OUTPUT0 ((__force s5p_gpio_pd_cfg_t)0x00) #define S5P_GPIO_PD_OUTPUT1 ((__force s5p_gpio_pd_cfg_t)0x01) #define S5P_GPIO_PD_INPUT ((__force s5p_gpio_pd_cfg_t)0x02) #define S5P_GPIO_PD_PREV_STATE ((__force s5p_gpio_pd_cfg_t)0x03)
1.s5p_gpio_set_pd_cfg()设置引脚的掉电模式寄存器
/** * s5p_gpio_set_pd_cfg() - set the configuration of a gpio power down mode * @pin: The pin number to configure the pull resistor. * @pd_cfg: The configuration for the pwer down mode configuration register. * * This function sets the configuration of the power down mode resistor for the * specified pin. It will return 0 if successful, or a negative error * code if the pin cannot support the requested power down mode. * */ extern int s5p_gpio_set_pd_cfg(unsigned int pin, s5p_gpio_pd_cfg_t pd_cfg);
功能：设置引脚的掉电模式寄存器
参数：@pin：要设置的引脚
@pd_cfg：要配置成的模式，当然是那四个宏之一
2.s5p_gpio_get_pd_cfg()取得引脚的掉电模式寄存器的值
/** * s5p_gpio_get_pd_cfg() - get the power down mode configuration of a gpio pin * @pin: The pin number to get the settings for * * Read the power down mode resistor value for the specified pin. */ extern s5p_gpio_pd_cfg_t s5p_gpio_get_pd_cfg(unsigned int pin);
功能：取得引脚的掉电模式寄存器的值
参数：@pin：要取得设置的引脚
/* Define values for the power down pull-{up,down} available for each gpio pin.
*
* These values control the state of the power down mode pull-{up,down}
* resistors available on most pins on the S5P series.
*/
#define S5P_GPIO_PD_UPDOWN_DISABLE ((__force s5p_gpio_pd_pull_t)0x00)
#define S5P_GPIO_PD_DOWN_ENABLE ((__force s5p_gpio_pd_pull_t)0x01)
#define S5P_GPIO_PD_UP_ENABLE ((__force s5p_gpio_pd_pull_t)0x03)
3.s5p_gpio_set_pd_pull()设置掉点模式的引脚的上下拉模式
/**
* s5p_gpio_set_pd_pull() - set the pull-{up,down} of a gpio pin power down mode
* @pin: The pin number to configure the pull resistor.
* @pd_pull: The configuration for the power down mode pull resistor.
*
* This function sets the configuration of the pull-{up,down} resistor for the
* specified pin. It will return 0 if successful, or a negative error
* code if the pin cannot support the requested pull setting.
*
*/
extern int s5p_gpio_set_pd_pull(unsigned int pin, s5p_gpio_pd_pull_t pd_pull);
功能：设置掉点模式的引脚的上下拉模式
参数：@pin：要设置的引脚
@pd_pull：要设置成什么模式，上下拉模式，当然是那三个宏拉
4.s5p_gpio_get_pd_pull()取得引脚的掉电模式上下拉电阻的设置
/** * s5p_gpio_get_pd_pull() - get the power down pull resistor config of gpio pin * @pin: The pin number to get the settings for * * Read the power mode pull resistor value for the specified pin. */ extern s5p_gpio_pd_pull_t s5p_gpio_get_pd_pull(unsigned int pin);
功能：取得引脚的掉电模式上下拉电阻的设置
参数：@pin：要取得设置的引脚
第五部分：关于中断引脚
这里我还不是很清楚，先不写了
1.s5p_register_gpio_interrupt()
/** * s5p_register_gpio_interrupt() - register interrupt support for a gpio group * @pin: The pin number from the group to be registered * * This function registers gpio interrupt support for the group that the * specified pin belongs to. * * The total number of gpio pins is quite large ob s5p series. Registering * irq support for all of them would be a resource waste. Because of that the * interrupt support for standard gpio pins is registered dynamically. * * It will return the irq number of the interrupt that has been registered * or -ENOMEM if no more gpio interrupts can be registered. It is allowed * to call this function more than once for the same gpio group (the group * will be registered only once). */ extern int s5p_register_gpio_interrupt(int pin);
功能：
参数：
2.s5p_register_gpioinit_bank()
/** s5p_register_gpioint_bank() - add gpio bank for further gpio interrupt
* registration (see s5p_register_gpio_interrupt function)
* @chain_irq: chained irq number for the gpio int handler for this bank
* @start: start gpio group number of this bank
* @nr_groups: number of gpio groups handled by this bank
*
* This functions registers initial information about gpio banks that
* can be later used by the s5p_register_gpio_interrupt() function to
* enable support for gpio interrupt for particular gpio group.
*/
#ifdef CONFIG_S5P_GPIO_INT
extern int s5p_register_gpioint_bank(int chain_irq, int start, int nr_groups);
#else
#define s5p_register_gpioint_bank(chain_irq, start, nr_groups) do { } while (0)
#endif