Linux 驱动学习笔记

最近用mini2440学习linux驱动，做一下笔记

LED驱动：

static int __init dev_init(void)

在驱动的初始化函数中经常看到，__init 前缀， 这个在下面文件中定义

file:/include/linux/init.h

/* These macros are used to mark some functions or * initialized data (doesn't apply to uninitialized data) * as `initialization' functions. The kernel can take this * as hint that the function is used only during the initialization * phase and free up used memory resources after * * Usage: * For functions: * * You should add __init immediately before the function name, like: * * static void __init initme(int x, int y) * { * extern int z; z = x * y; * }

主要是将这个函数放在init段section中，这样可以在执行完成后，释放内存。

关于s3c2410_gpio_cfgpin函数，只能了解到，设置某个GPIO的功能，但是怎么实现的没看明白，好像还用到虚拟地址了，最后也没有发现是怎么配置的GPCON寄存器的，

void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function) { void __iomem *base = S3C24XX_GPIO_BASE(pin); unsigned long mask; unsigned long con; unsigned long flags; if (pin < S3C2410_GPIO_BANKB) { mask = 1 << S3C2410_GPIO_OFFSET(pin); } else { mask = 3 << S3C2410_GPIO_OFFSET(pin)*2; } switch (function) { case S3C2410_GPIO_LEAVE: mask = 0; function = 0; break; case S3C2410_GPIO_INPUT: case S3C2410_GPIO_OUTPUT: case S3C2410_GPIO_SFN2: case S3C2410_GPIO_SFN3: if (pin < S3C2410_GPIO_BANKB) { function -= 1; function &= 1; function <<= S3C2410_GPIO_OFFSET(pin); } else { function &= 3; function <<= S3C2410_GPIO_OFFSET(pin)*2; } } /* modify the specified register wwith IRQs off */ local_irq_save(flags); con = __raw_readl(base + 0x00); con &= ~mask; con |= function; __raw_writel(con, base + 0x00); local_irq_restore(flags); }

而且，后面

有个地方讲不通： （这个地方应该是都不满足 switch 的条件，所以， function 不改变）

#define S3C2410_GPIO_LEAVE   (0xFFFFFFFF)

#define S3C2410_GPIO_INPUT   (0xFFFFFFF0)  /* not available on A */

#define S3C2410_GPIO_OUTPUT  (0xFFFFFFF1)

#define S3C2410_GPIO_IRQ     (0xFFFFFFF2)   /* not available for all */

#define S3C2410_GPIO_SFN2    (0xFFFFFFF2)  /* bank A => addr/cs/nand */

#define S3C2410_GPIO_SFN3    (0xFFFFFFF3)  /* not available on A */

 

而

#define S3C2410_GPB5_OUTP    (0x01 << 10)

所以，

s3c2410_gpio_cfgpin(S3C2410_GPB5, S3C2410_GPB5_OUTP);

switch (function)

根本对不上号？

 

s3c2410_gpio_cfgpin(S3C2410_GPB5, S3C2410_GPB5_OUTP);

s3c2410_gpio_cfgpin(37, S3C2410_GPB5_OUTP);

s3c2410_gpio_cfgpin(37,  0x01 << 10 );

剩下的37怎么变换出mask，怎么得到GPCON的地址没看懂？

这个在 /arch/arm/mach-s3c2410/include/mach/regs-gpio.h 中定义

#define S3C2410_GPB5         S3C2410_GPIONO(S3C2410_GPIO_BANKB, 5)

#define S3C2410_GPB5_INP     (0x00 << 10)

#define S3C2410_GPB5_OUTP    (0x01 << 10)

#define S3C2410_GPB5_nXBACK  (0x02 << 10)

 

S3C2410_GPIONO (S3C2410_GPIO_BANKB , 5)

 

#define S3C2410_GPIONO (bank,offset) ((bank) + (offset))

#define S3C2410_GPIO_BANKA   (32*0)

#define S3C2410_GPIO_BANKB    (32*1)

 

可以看一下这篇文章：

http://www.linuxidc.com/Linux/2011-06/37322.htm