linux lcd设备驱动剖析二

上一节中，分析了s3c2410fb,c的入口出口函数，以及一些重要结构体的分析，初步知道了这是一个平台驱动的架构。

上一节文章链接：http://blog.csdn.net/lwj103862095/article/details/18188259

上一节讲到probe函数就没继续往下深究了，这一节里，我们来详细分析s3c24xxfb_probe函数，整体分析如下：

static int __init s3c24xxfb_probe(struct platform_device *pdev,  enum s3c_drv_type drv_type){struct s3c2410fb_info *info;struct s3c2410fb_display *display;struct fb_info *fbinfo;struct s3c2410fb_mach_info *mach_info;  /* 包含s3c2410fb_display */struct resource *res;int ret;int irq;int i;int size;u32 lcdcon1;/*  s3c24xx_fb_set_platdata()里会设置platform_data *  tq2440_machine_init()函数调用s3c24xx_fb_set_platdata(&tq2440_fb_info); *  所以这里传入来的platform_data就是tq2440_fb_info结构体实例 */mach_info = pdev->dev.platform_data;/* 执行完上面的语句后mach_info指向tq2440_fb_info结构体，而不为NULL  */if (mach_info == NULL) {dev_err(&pdev->dev,"no platform data for lcd, cannot attach\n");return -EINVAL;/* 表示无效的参数 */}/* tq2440_fb_info设置了default_display = 0，num_displays = 1，故这句不会执行 */if (mach_info->default_display >= mach_info->num_displays) {dev_err(&pdev->dev, "default is %d but only %d displays\n",mach_info->default_display, mach_info->num_displays);return -EINVAL;}/* display指向tq2440_lcd_cfg，关于LCD屏相关参数的设置 */display = mach_info->displays + mach_info->default_display;/* 通过平台设备platform_device获得IRQ * platform_get_irq其实是调用platform_get_resource(dev, IORESOURCE_IRQ, num) */irq = platform_get_irq(pdev, 0);if (irq < 0) {dev_err(&pdev->dev, "no irq for device\n");return -ENOENT;}/* 分配一个fb_info结构体,第一参数不为0表示，额外多申请的空间 *用来存放额外的数据，这里用来存放s3c2410fb_info额外的数据 *  比如:clk，resource，io,irq_base,drv_type等额外信息 */fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);if (!fbinfo)return -ENOMEM;/* 返回NULL表示失败 *//* 相当于pdev->dev->driver_data = fbinfo */platform_set_drvdata(pdev, fbinfo);/* 在framebuffer_alloc函数里info->par指向了额外多申请内存空间的首地址 */info = fbinfo->par;/* 将私有数据赋给info指针变量 */info->dev = &pdev->dev;/* 指定struct s3c2410fb_info中dev为平台设备中的dev */info->drv_type = drv_type;/* 驱动类型， DRV_S3C2410还是DRV_S3C2412 *//*  通过平台设备platform_device获得资源(IO) */res = platform_get_resource(pdev, IORESOURCE_MEM, 0);if (res == NULL) {dev_err(&pdev->dev, "failed to get memory registers\n");ret = -ENXIO;goto dealloc_fb;}size = (res->end - res->start) + 1;/* 资源的大小 *//* 申请以res->start地址开始大小为size的I/O内存 */info->mem = request_mem_region(res->start, size, pdev->name);if (info->mem == NULL) {dev_err(&pdev->dev, "failed to get memory region\n");ret = -ENOENT;goto dealloc_fb;}/* 映射I/O地址，其实就是将S3C2440的LCD首寄存器(LCDCON1)的物理地址映射为虚拟地址 */info->io = ioremap(res->start, size);if (info->io == NULL) {dev_err(&pdev->dev, "ioremap() of registers failed\n");ret = -ENXIO;goto release_mem;}/* 这里相当于info->irq_base = info->io + 0x54，刚好是LCDINTPND寄存器的地址 */info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE);dprintk("devinit\n");/* 驱动名，fbinfo->fix.id = s3c2410fb */strcpy(fbinfo->fix.id, driver_name);/* Stop the video */lcdcon1 = readl(info->io + S3C2410_LCDCON1);/* 禁止Video output */writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1);/* 设置fb_info结构体通用的固定参数fb_fix_screeninfo结构体 */fbinfo->fix.type   = FB_TYPE_PACKED_PIXELS;fbinfo->fix.type_aux    = 0;fbinfo->fix.xpanstep    = 0;fbinfo->fix.ypanstep    = 0;fbinfo->fix.ywrapstep    = 0;fbinfo->fix.accel    = FB_ACCEL_NONE;/* 无硬件加速 *//* 设置fb_info结构体通用的可变参数fb_var_screeninfo结构体 */fbinfo->var.nonstd    = 0;fbinfo->var.activate    = FB_ACTIVATE_NOW;fbinfo->var.accel_flags     = 0;fbinfo->var.vmode    = FB_VMODE_NONINTERLACED;/* 设置fb_ops结构体 */fbinfo->fbops    = &s3c2410fb_ops;fbinfo->flags    = FBINFO_FLAG_DEFAULT;/* 设置假调色板 */fbinfo->pseudo_palette      = &info->pseudo_pal;/* palette_buffer[i] = 0x80000000，清空调色板 */for (i = 0; i < 256; i++)info->palette_buffer[i] = PALETTE_BUFF_CLEAR;/* 申请中断，s3c2410fb_irq是中断处理函数 */ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info);if (ret) {dev_err(&pdev->dev, "cannot get irq %d - err %d\n", irq, ret);ret = -EBUSY;goto release_regs;}/* 获取lcd时钟 */info->clk = clk_get(NULL, "lcd");if (!info->clk || IS_ERR(info->clk)) {printk(KERN_ERR "failed to get lcd clock source\n");ret = -ENOENT;goto release_irq;}/* 使能lcd时钟 */clk_enable(info->clk);dprintk("got and enabled clock\n");msleep(1);/* find maximum required memory size for display *//* 计算出lcd的显存大小，显存大小为width * height * bpp所以还要左移3位，     * 即刚好一帧大小空间，前面计算出来的是多少bit，计算出显存为多少字节。     * 显示配置有可能有多个，所以呢，这个for循环计算出的是最大显存大小。 */for (i = 0; i < mach_info->num_displays; i++) {  /* 这里mach_info->num_displays = 1 */unsigned long smem_len = mach_info->displays[i].xres;/* x方向分辨率 */smem_len *= mach_info->displays[i].yres;/* y方向分辨率 */smem_len *= mach_info->displays[i].bpp;/* bpp */smem_len >>= 3;/* smem_len除以8 */if (fbinfo->fix.smem_len < smem_len)fbinfo->fix.smem_len = smem_len;}/* Initialize video memory */ret = s3c2410fb_map_video_memory(fbinfo);/* 分配显存 */if (ret) {printk(KERN_ERR "Failed to allocate video RAM: %d\n", ret);ret = -ENOMEM;goto release_clock;}dprintk("got video memory\n");/* display指向tq2440_lcd_cfg */fbinfo->var.xres = display->xres;/* 设置x方向的分辨率 */fbinfo->var.yres = display->yres;/* 设置y方向的分辨率 */fbinfo->var.bits_per_pixel = display->bpp;/* 设置bpp位数 *//* 初始化LCD相关的寄存器 */s3c2410fb_init_registers(fbinfo);/* 检查可变参数 */s3c2410fb_check_var(&fbinfo->var, fbinfo);/* 注册fb_info结构体 */ret = register_framebuffer(fbinfo);if (ret < 0) {printk(KERN_ERR "Failed to register framebuffer device: %d\n",ret);goto free_video_memory;}/* create device files */ret = device_create_file(&pdev->dev, &dev_attr_debug);if (ret) {printk(KERN_ERR "failed to add debug attribute\n");}/* TQ2440开发板内核启动时打印的信息,fb0: s3c2410fb frame buffer device  */printk(KERN_INFO "fb%d: %s frame buffer device\n",fbinfo->node, fbinfo->fix.id);return 0;free_video_memory:s3c2410fb_unmap_video_memory(fbinfo);release_clock:clk_disable(info->clk);/* 禁止lcd时钟 */clk_put(info->clk);/* 删除lcd时钟 */release_irq:free_irq(irq, info);/* 释放IRQ */release_regs:iounmap(info->io);/* 解除映射 */release_mem:release_resource(info->mem);/* 释放资源 */kfree(info->mem);/* 释放刚申请的内存 */dealloc_fb:platform_set_drvdata(pdev, NULL);/* 相当于pdev->dev->driver_data = NULL */framebuffer_release(fbinfo);/* 释放fb_info结构体 */return ret;}

拆分详解：

一、获得平台数据

mach_info = pdev->dev.platform_data;/* 执行完上面的语句后mach_info指向tq2440_fb_info结构体，而不为NULL  */if (mach_info == NULL) {dev_err(&pdev->dev,"no platform data for lcd, cannot attach\n");return -EINVAL;/* 表示无效的参数 */}

s3c24xx_fb_set_platdata()里会设置platform_data，tq2440_machine_init()函数调用s3c24xx_fb_set_platdata(&tq2440_fb_info);
所以这里传入来的platform_data就是tq2440_fb_info结构体实例。

static void __init tq2440_machine_init(void){/* 初始化tq2440_fb_info实体结构体 */s3c24xx_fb_set_platdata(&tq2440_fb_info);s3c_i2c0_set_platdata(NULL);/* 添加tq2440_devices到内核，它是platform_device类的设备 */platform_add_devices(tq2440_devices, ARRAY_SIZE(tq2440_devices));EmbedSky_machine_init();s3c2410_gpio_setpin(S3C2410_GPG12, 0);s3c2410_gpio_cfgpin(S3C2410_GPG12, S3C2410_GPIO_OUTPUT);s3c24xx_udc_set_platdata(&EmbedSky_udc_cfg);}

s3c24xx_fb_set_platdata函数将tq2440_fb_info拷贝到s3c2410fb_mach_info，并将s3c_device_lcd.dev.platform_data指向tq2440_fb_info

void __init s3c24xx_fb_set_platdata(struct s3c2410fb_mach_info *pd){struct s3c2410fb_mach_info *npd;/* 申请分配s3c2410fb_mach_info大小的内存 */npd = kmalloc(sizeof(*npd), GFP_KERNEL);if (npd) {/* 拷贝s3c2410fb_mach_info型实体给npd */memcpy(npd, pd, sizeof(*npd));/* 最后将s3c2410fb_mach_info型实体赋给platform_data */s3c_device_lcd.dev.platform_data = npd;} else {printk(KERN_ERR "no memory for LCD platform data\n");}}

二、设置s3c2410fb_display指向tq2440_lcd_cfg

/* tq2440_fb_info设置了default_display = 0，num_displays = 1，故这句不会执行 */if (mach_info->default_display >= mach_info->num_displays) {dev_err(&pdev->dev, "default is %d but only %d displays\n",mach_info->default_display, mach_info->num_displays);return -EINVAL;}/* display指向tq2440_lcd_cfg，关于LCD屏相关参数的设置 */display = mach_info->displays + mach_info->default_display;

三、获得IRQ资源

irq = platform_get_irq(pdev, 0);if (irq < 0) {dev_err(&pdev->dev, "no irq for device\n");return -ENOENT;}

四、分配fb_info内存

fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);if (!fbinfo)return -ENOMEM;/* 返回NULL表示失败 */

framebuffer_alloc第一参数不为0表示，额外多申请的空间，用来存放额外的数据，这里用来存放s3c2410fb_info额外的数据，比如:clk，resource，io,irq_base,drv_type等额外信息。
五、设置s3c2410fb_info结构体

/* 相当于pdev->dev->driver_data = fbinfo */platform_set_drvdata(pdev, fbinfo);/* 在framebuffer_alloc函数里info->par指向了额外多申请内存空间的首地址 */info = fbinfo->par;/* 将私有数据赋给info指针变量 */info->dev = &pdev->dev;/* 指定struct s3c2410fb_info中dev为平台设备中的dev */info->drv_type = drv_type;/* 驱动类型， DRV_S3C2410还是DRV_S3C2412 */

六、获取IO资源，映射IO

/*  通过平台设备platform_device获得资源(IO) */res = platform_get_resource(pdev, IORESOURCE_MEM, 0);if (res == NULL) {dev_err(&pdev->dev, "failed to get memory registers\n");ret = -ENXIO;goto dealloc_fb;}size = (res->end - res->start) + 1;/* 资源的大小 *//* 申请以res->start地址开始大小为size的I/O内存 */info->mem = request_mem_region(res->start, size, pdev->name);if (info->mem == NULL) {dev_err(&pdev->dev, "failed to get memory region\n");ret = -ENOENT;goto dealloc_fb;}/* 映射I/O地址，其实就是将S3C2440的LCD首寄存器(LCDCON1)的物理地址映射为虚拟地址 */info->io = ioremap(res->start, size);if (info->io == NULL) {dev_err(&pdev->dev, "ioremap() of registers failed\n");ret = -ENXIO;goto release_mem;}/* 这里相当于info->irq_base = info->io + 0x54，刚好是LCDINTPND寄存器的地址 */info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE);

七、读写LCDCON1，禁止视频数据输出

/* Stop the video */lcdcon1 = readl(info->io + S3C2410_LCDCON1);/* 禁止Video output */writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1);

八、设置fb_info结构体的固定参数（fb_fix_screeninfo），可变参数（fb_var_screeninfo），fbops结构体，flags，假调色板（pseudo_palette）等

/* 设置fb_info结构体通用的固定参数fb_fix_screeninfo结构体 */fbinfo->fix.type   = FB_TYPE_PACKED_PIXELS;fbinfo->fix.type_aux    = 0;fbinfo->fix.xpanstep    = 0;fbinfo->fix.ypanstep    = 0;fbinfo->fix.ywrapstep    = 0;fbinfo->fix.accel    = FB_ACCEL_NONE;/* 无硬件加速 *//* 设置fb_info结构体通用的可变参数fb_var_screeninfo结构体 */fbinfo->var.nonstd    = 0;fbinfo->var.activate    = FB_ACTIVATE_NOW;fbinfo->var.accel_flags     = 0;fbinfo->var.vmode    = FB_VMODE_NONINTERLACED;/* 设置fb_ops结构体 */fbinfo->fbops    = &s3c2410fb_ops;fbinfo->flags    = FBINFO_FLAG_DEFAULT;/* 设置假调色板 */fbinfo->pseudo_palette      = &info->pseudo_pal;/* palette_buffer[i] = 0x80000000，清空调色板 */for (i = 0; i < 256; i++)info->palette_buffer[i] = PALETTE_BUFF_CLEAR;

九、申请中断、获取LCD时钟，使能LCD时钟

/* 申请中断，s3c2410fb_irq是中断处理函数 */ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info);if (ret) {dev_err(&pdev->dev, "cannot get irq %d - err %d\n", irq, ret);ret = -EBUSY;goto release_regs;}/* 获取lcd时钟 */info->clk = clk_get(NULL, "lcd");if (!info->clk || IS_ERR(info->clk)) {printk(KERN_ERR "failed to get lcd clock source\n");ret = -ENOENT;goto release_irq;}/* 使能lcd时钟 */clk_enable(info->clk);dprintk("got and enabled clock\n");

十、计算显存大小、分配显存内存

/* 计算出lcd的显存大小，显存大小为width * height * bpp所以还要左移3位，     * 即刚好一帧大小空间，前面计算出来的是多少bit，计算出显存为多少字节。     * 显示配置有可能有多个，所以呢，这个for循环计算出的是最大显存大小。 */for (i = 0; i < mach_info->num_displays; i++) {  /* 这里mach_info->num_displays = 1 */unsigned long smem_len = mach_info->displays[i].xres;/* x方向分辨率 */smem_len *= mach_info->displays[i].yres;/* y方向分辨率 */smem_len *= mach_info->displays[i].bpp;/* bpp */smem_len >>= 3;/* smem_len除以8 */if (fbinfo->fix.smem_len < smem_len)fbinfo->fix.smem_len = smem_len;}/* Initialize video memory */ret = s3c2410fb_map_video_memory(fbinfo);/* 分配显存 */if (ret) {printk(KERN_ERR "Failed to allocate video RAM: %d\n", ret);ret = -ENOMEM;goto release_clock;}

十一、设置fb_info结构体中的可变参数的x、y分辨率以及BPP为tq2440_lcd_cfg中的x、y分辨率和BPP

/* display指向tq2440_lcd_cfg */fbinfo->var.xres = display->xres;/* 设置x方向的分辨率 */fbinfo->var.yres = display->yres;/* 设置y方向的分辨率 */fbinfo->var.bits_per_pixel = display->bpp;/* 设置bpp位数 */

十二、LCD相关寄存器的设置和fb_info的可变参数的检测

/* 初始化LCD相关的寄存器 */s3c2410fb_init_registers(fbinfo);/* 检查可变参数 */s3c2410fb_check_var(&fbinfo->var, fbinfo);

十三、注册fb_info结构体

/* 注册fb_info结构体 */ret = register_framebuffer(fbinfo);if (ret < 0) {printk(KERN_ERR "Failed to register framebuffer device: %d\n",ret);goto free_video_memory;}