Linux设备驱动--LCD平台设备与驱动（smdk2440）

转自http://blog.csdn.net/q1302182594/article/details/52368040

  Host：Ubuntu14.04（64bit）

    Target：smdk2440

    Kernel：Linux-2.6.39.4

    类似于《Linux设备驱动--WDT平台设备与驱动》，本文再以LCD为例进行说明。本文的源码均来自linux内核（linux-2.6.39.4貌似对mini2440 LCD移植还不完善，因此本文以smdk2440为例，在源码中已经完美支持该开发板的LCD）。

2 平台设备

2.1 定义

（1）平台设备

    定义全局变量s3c_device_lcd，并且通过EXPORT_SYMBOL(s3c_device_lcd)使其在别的源文件可见：

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1. struct platform_device s3c_device_lcd = {   
2.     .name         = "s3c2410-  lcd",                                  //   //设备名称                                                                                                           
3.     .id       = -1,                   
4.     .num_resources    = ARRAY_SIZE(s3c_lcd_resource),//设备使用各类资源的数量
5.     .resource     = s3c_lcd_resource,   ////设备使用的资源
6.     .dev              = {  
7.         .dma_mask       = &s3c_device_lcd_dmamask,  
8.         .coherent_dma_mask  = 0xffffffffUL  
9.     }     
10. };  
11. EXPORT_SYMBOL(s3c_device_lcd);  

struct platform_device s3c_device_lcd = {     .name         = "s3c2410-lcd",                                                                                                                                                   .id       = -1,                     .num_resources    = ARRAY_SIZE(s3c_lcd_resource),     .resource     = s3c_lcd_resource,     .dev              = {        .dma_mask       = &s3c_device_lcd_dmamask,        .coherent_dma_mask  = 0xffffffffUL    }   };EXPORT_SYMBOL(s3c_device_lcd);

源文件：arch/arm/plat-s3c24xx/devs.c

（2）平台资源

    上述LCD设备所引用的平台设备资源如下所定义：

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1. static struct resource s3c_lcd_resource[] = {  
2.     [0] = {  
3.         .start = S3C24XX_PA_LCD, /* 0x4D000000 */  
4.         .end   = S3C24XX_PA_LCD + S3C24XX_SZ_LCD - 1,/* S3C24XX_SZ_LCD=0x00100000(1M) */                                                                                                                           
5.         .flags = IORESOURCE_MEM, /* 0x00000200 */                                                                                                                                                
6.     },                                                                                                                                                                          
7.     [1] = {                                                                                                                                                                     
8.         .start = IRQ_LCD, /* 32 */                                                                                                                                                      
9.         .end   = IRQ_LCD,                                                                                                                                                       
10.         .flags = IORESOURCE_IRQ, /* 0x00000400 */                                                                                                                                                
11.     }                                                                                                                                                                                                                                                                                                                                                    
12. };   

static struct resource s3c_lcd_resource[] = {    [0] = {        .start = S3C24XX_PA_LCD, /* 0x4D000000 */        .end   = S3C24XX_PA_LCD + S3C24XX_SZ_LCD - 1,/* S3C24XX_SZ_LCD=0x00100000(1M) */                                                                                                                                 .flags = IORESOURCE_MEM, /* 0x00000200 */                                                                                                                                                  },                                                                                                                                                                            [1] = {                                                                                                                                                                           .start = IRQ_LCD, /* 32 */                                                                                                                                                            .end   = IRQ_LCD,                                                                                                                                                             .flags = IORESOURCE_IRQ, /* 0x00000400 */                                                                                                                                                  }                                                                                                                                                                                                                                                                                                                                                  }; 

源文件：arch/arm/plat-s3c24xx/devs.c

2.2 引用

    定义一个平台设备数组smdk2440_devices，该数组包含了smdk2440开发板的所有平台设备，其中当然包括上述s3c_device_lcd，如下第3行所示：

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1. static struct platform_device *smdk2440_devices[] __initdata = {  
2.     &s3c_device_ohci,  
3.     &s3c_device_lcd,  
4.     &s3c_device_wdt,  
5.     &s3c_device_i2c0,  
6.     &s3c_device_iis,  
7. };  

static struct platform_device *smdk2440_devices[] __initdata = {    &s3c_device_ohci,    &s3c_device_lcd,    &s3c_device_wdt,    &s3c_device_i2c0,    &s3c_device_iis,};

源文件：arch/arm/mach-s3c2440/mach-smdk2440.c

2.3 注册

（1）注册函数    

    在smdk2440_machine_init（）函数中调用platform_add_devices（）函数将上述smdk2440_devices注册到系统，即可完成平台设备的注册，如下第4行所示：

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1. static void __init smdk2440_machine_init(void)  
2. {  
3.     s3c24xx_fb_set_platdata(&smdk2440_fb_info);  
4.     s3c_i2c0_set_platdata(NULL);  
5.   
6.     platform_add_devices(smdk2440_devices, ARRAY_SIZE(smdk2440_devices));  
   int platform_add_devices(struct platform_device **devs, int num)
   {
       int i, ret = 0;
       for (i = 0; i < num; i++) {
           ret = platform_device_register(devs[i]);
           if (ret) {
               while (–i >= 0)
                   platform_device_unregister(devs[i]);
               break;
           }
       }
       return ret;
   }
7.     smdk_machine_init();  
8. }  

static void __init smdk2440_machine_init(void){    s3c24xx_fb_set_platdata(&smdk2440_fb_info);    s3c_i2c0_set_platdata(NULL);    platform_add_devices(smdk2440_devices, ARRAY_SIZE(smdk2440_devices));    smdk_machine_init();}

源文件：arch/arm/mach-s3c2440/mach-smdk2440.c

（2）注册时机

    上述smdk2440_machine_init（）函数是何时被调用的呢？答案是在内核初始化设备的时候，如下第6行所示：

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1. MACHINE_START(S3C2440, "SMDK2440")  
2.     /* Maintainer: Ben Dooks <[e-mail]> */  
3.     .boot_params    = S3C2410_SDRAM_PA + 0x100, /* 0x30000100 */  
4.     .init_irq   = s3c24xx_init_irq,  
5.     .map_io     = smdk2440_map_io,  
6.     .init_machine   = smdk2440_machine_init,  
7.     .timer      = &s3c24xx_timer,  
8. MACHINE_END     

MACHINE_START(S3C2440, "SMDK2440")    /* Maintainer: Ben Dooks <[e-mail]> */    .boot_params    = S3C2410_SDRAM_PA + 0x100, /* 0x30000100 */    .init_irq   = s3c24xx_init_irq,    .map_io     = smdk2440_map_io,    .init_machine   = smdk2440_machine_init,    .timer      = &s3c24xx_timer,MACHINE_END   

源文件：arch/arm/mach-s3c2440/mach-smdk2440.c

3 平台驱动

3.1 定义

    为了和平台设备匹配，平台驱动的name要与平台设备的name一致：

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1. static struct platform_driver s3c2410fb_driver = {  
2.     .probe      = s3c2410fb_probe,   
3.     .remove     = __devexit_p(s3c2410fb_remove),  
4.     .suspend    = s3c2410fb_suspend,  
5.     .resume     = s3c2410fb_resume,  
6.     .driver     = {    
7.         .name   = "s3c2410-lcd",                                                                                                                                         
8.         .owner  = THIS_MODULE,  
9.     },     
10. };  

static struct platform_driver s3c2410fb_driver = {    .probe      = s3c2410fb_probe,     .remove     = __devexit_p(s3c2410fb_remove),    .suspend    = s3c2410fb_suspend,    .resume     = s3c2410fb_resume,    .driver     = {          .name   = "s3c2410-lcd",                                                                                                                                               .owner  = THIS_MODULE,    },   };

源文件：drivers/video/s3c2410fb.c

    上述s3c2410fb_probe、s3c2410fb_remove、s3c2410fb_shutdown、s3c2410fb_suspend以及s3c2410fb_resume都在同一个源文件中定义，详见源文件drivers/video/s3c2410fb.c。

    上述s3c2410fb_probe（）调用s3c24xxfb_probe（），并且在s3c24xxfb_probe（）中实现framebuffer的创建，初始化与注册，详见《Linux设备驱动--framebuffer》。

3.2 注册

     在模块加载函数s3c2410fb_init（）中调用platform_driver_register（）函数注册上述平台驱动s3c2410fb_driver：

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1. int __init s3c2410fb_init(void)                                                                                                                                                 
2. {                                                                                                                                                                               
3.     int ret = platform_driver_register(&s3c2410fb_driver);                                                                                                                      
4.                                                                                                                                                                                                                                                                                                                                                      
5.     if (ret == 0)                                                                                                                                                               
6.         ret = platform_driver_register(&s3c2412fb_driver);                                                                                                                      
7.                                                                                                                                                                                 
8.     return ret;                                                                                                                                                                 
9. }    

int __init s3c2410fb_init(void)                                                                                                                                               {                                                                                                                                                                                 int ret = platform_driver_register(&s3c2410fb_driver);                                                                                                                                                                                                                                                                                                                                                                                                                                                                           if (ret == 0)                                                                                                                                                                     ret = platform_driver_register(&s3c2412fb_driver);                                                                                                                                                                                                                                                                                                      return ret;                                                                                                                                                               }  

源文件：drivers/video/s3c2410fb.c

4 设备与驱动匹配

    同《Linux设备驱动--WDT平台设备与驱动》第4节。

参考资料

[1]Linux下LCD驱动详细分析（一）

[2]Linux LCD驱动参数的配置与编译(完全)

[3]Linux的LCD驱动 

[4]Linux下LCD编程

[5]Tiny 4412 lcd 驱动分析

[6]tiny4412LCD驱动加字符显示

[7]平台设备的识别