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;
}
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 */
}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);
}
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");
}
}
/* 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;
irq = platform_get_irq(pdev, 0);
if (irq < 0) {
dev_err(&pdev->dev, "no irq for device\n");
return -ENOENT;
}fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);
if (!fbinfo)
return -ENOMEM; /* 返回NULL表示失败 */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 */
/* 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);
/* 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");
/* 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;
}
/* 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;
}