Linux 驅動學習筆記

最近用mini2440學習linux驅動，做一下筆記

LED驅動：

static int __init dev_init(void)

在驅動的初始化函數中經常看到，__init 首碼，
這個在下面檔案中定義

file:/include/linux/init.h

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

主要是將這個函數放在init段section中，這樣可以在執行完成後，釋放記憶體。

關於s3c2410_gpio_cfgpin函數，只能瞭解到，設定某個GPIO的功能，但是怎麼實現的沒看明白，好像還用到虛擬位址了，最後也沒有發現是怎麼配置的GPCON寄存器的，

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

而且，後面

有個地方講不通：

（這個地方應該是都不滿足
switch
的條件，所以，
function
不改變）

#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)

根本對不上號？

 

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怎麼變換出mask，怎麼得到GPCON的地址沒看懂？

這個在
/arch/arm/mach-s3c2410/include/mach/regs-gpio.h
中定義

#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)

 

可以看一下這篇文章：

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