S5PV210 显示控制器及framebuffer驱动s3c-fb.c中probe函数分析

    三星SOC芯片上集成了显示控制器（有称作fimd的，Fully Interactive Mobile Display）。它的驱动分为mainline版本的和legacy版本的，mainline版本的是通用的，由Ben Dooks <[email protected]> 管理着的，代码比较规范。下面我们来分析一下这个驱动，这个驱动在driver/video/里，文件名是s3c-fb.c 与其相关的，主要还有arch/arm/plat-s5p/dev-fimd0.c和arch/arm/mach-XXXX/setup-fimd0.c 。 前者是定义platform device的，后者是定义一些比较depend on 具体芯片的东西，例如GPIO。

 

       我们这里主要分析s3c-fb.c中的probe函数， probe函数里最重要的是s3c_fb_probe_win函数，一会也一并分析。

       首先解释一个概念，很多书中有framebuffer这个概念，但是在三星的显示控制器文档或代码中，常出现win或window的概念，显示控制器可以控制0~5个windows，代码中分给它们分别编号win0, win1,win2......这里一张win或window就对应一个framebuffer, 每个framebuffer有自己的一个FBI（fb_info）结构。

      代码中， 显示控制器是s3c_fb结构体， window是s3c_fb_win结构体。

      代码中有两种data，一种是platform data（在板文件中定义），另一种是driver data(在驱动文件中定义)，在它们各自的结构体里面，又可以分为两部份，一是用于sfb的data, 另一是用于win的data。

      framebuffer是fb_info结构体，里面主要存储设置参数的数据结构有两个，fb_var_screeninfo和fb_fix_screeninfo结构体。

 

 ************************************************ platform data***************************************************

static struct s3c_fb_platdata smdkv210_lcd0_pdata __initdata = {
 .win[0]  = &smdkv210_fb_win0,                  -------->用于win的部分，下文称作“platform data中win的部分”
 .vidcon0  = VIDCON0_VIDOUT_RGB | VIDCON0_PNRMODE_RGB,      -------->下面开始是sfb的部分，
 .vidcon1  = VIDCON1_INV_HSYNC | VIDCON1_INV_VSYNC,
 .setup_gpio  = s5pv210_fb_gpio_setup_24bpp,
 };

static struct s3c_fb_platdata smdkv210_lcd0_pdata __initdata = {
 .win[0]  = &smdkv210_fb_win0,                  -------->用于win的部分，下文称作“platform data中win的部分”
 .vidcon0  = VIDCON0_VIDOUT_RGB | VIDCON0_PNRMODE_RGB,      -------->下面开始是sfb的部分，
 .vidcon1  = VIDCON1_INV_HSYNC | VIDCON1_INV_VSYNC,
 .setup_gpio  = s5pv210_fb_gpio_setup_24bpp,
 };

************************************************ driver data***************************************************

static struct s3c_fb_driverdata s3c_fb_data_s5pv210 = {
 .variant = {                                             ---------->用于sfb的driverdata
 .nr_windows  = 5,
 .vidtcon  = VIDTCON0,
 .wincon  = WINCON(0),
 .winmap  = WINxMAP(0),
 .keycon  = WKEYCON,
 .osd  = VIDOSD_BASE,
 .osd_stride  = 16,
 .buf_start  = VIDW_BUF_START(0),
 .buf_size  = VIDW_BUF_SIZE(0),
 .buf_end  = VIDW_BUF_END(0),


 .palette = {
 [0] = 0x2400,
 [1] = 0x2800,
 [2] = 0x2c00,
 [3] = 0x3000,
 [4] = 0x3400,
 },


 .has_shadowcon= 1,
 .has_blendcon  = 1,
 .has_alphacon  = 1,
 .has_clksel  = 1,
 .has_fixvclk  = 1,
 },
 .win[0]  = &s3c_fb_data_s5p_wins[0],      ---------->用于各个win的部分，下文称作“driver data中win的部份”
 .win[1]  = &s3c_fb_data_s5p_wins[1],
 .win[2]  = &s3c_fb_data_s5p_wins[2],
 .win[3]  = &s3c_fb_data_s5p_wins[3],
 .win[4]  = &s3c_fb_data_s5p_wins[4],
 };

static struct s3c_fb_driverdata s3c_fb_data_s5pv210 = {
 .variant = {                                             ---------->用于sfb的driverdata
 .nr_windows  = 5,
 .vidtcon  = VIDTCON0,
 .wincon  = WINCON(0),
 .winmap  = WINxMAP(0),
 .keycon  = WKEYCON,
 .osd  = VIDOSD_BASE,
 .osd_stride  = 16,
 .buf_start  = VIDW_BUF_START(0),
 .buf_size  = VIDW_BUF_SIZE(0),
 .buf_end  = VIDW_BUF_END(0),
 

 .palette = {
 [0] = 0x2400,
 [1] = 0x2800,
 [2] = 0x2c00,
 [3] = 0x3000,
 [4] = 0x3400,
 },
 

 .has_shadowcon= 1,
 .has_blendcon  = 1,
 .has_alphacon  = 1,
 .has_clksel  = 1,
 .has_fixvclk  = 1,
 },
 .win[0]  = &s3c_fb_data_s5p_wins[0],      ---------->用于各个win的部分，下文称作“driver data中win的部份”
 .win[1]  = &s3c_fb_data_s5p_wins[1],
 .win[2]  = &s3c_fb_data_s5p_wins[2],
 .win[3]  = &s3c_fb_data_s5p_wins[3],
 .win[4]  = &s3c_fb_data_s5p_wins[4],
 };

************************************************ s3c_fb_probe() ***************************************************

static int __devinit s3c_fb_probe(struct platform_device *pdev)
 {
 const struct platform_device_id *platid;                    -------> 因为一个驱动要适合很多版本的设备，每个版本的设备的设置 参数都不一样，所以要用到platid来选择哪个版本的设备，像“s5pv210-fb”, "s3c2443-fb"..., 这些就是platid(也在s3c-fb.c中定义了)， 也表明了，这个驱动能适合于这些设备。
 struct s3c_fb_driverdata *fbdrv;                         ----> driver data
 struct device *dev = &pdev->dev;
 struct s3c_fb_platdata *pd;                             ----> platform data
 struct s3c_fb *sfb;                                   -----> 一个最重要的数据结据， 它代表了一个显示控制器，显示控制器的所有东东都放在这里了。但这里把它做成一个局部变量了。
 struct resource *res;                              -----> 资源
 int win;
 int default_win;
 ...

 platid = platform_get_device_id(pdev);  ----> 从platform device 里 的id_entry 变量中获取platid，由一个宏实现

 fbdrv = (struct s3c_fb_driverdata *)platid->driver_data;    ---> 获取platid对应的driver data，driver data在s3c-fb.c中定义，主要是一定设置参数

...

 pd = pdev->dev.platform_data;  --> 获取platform data，它在板文件中定义，这个data里包含了关于显示控制器的数据，也包含了win的数据。


...

 sfb = kzalloc(sizeof(struct s3c_fb), GFP_KERNEL);         ------> 给这个最重要的结构分配内存空间


...

 sfb->dev = dev;                      ---> 向sfb 填入 显示控制器的 device 结构体
 sfb->pdata = pd;                   ---> 向sfb 填入 显示控制器的 platform data 结构体
 sfb->variant = fbdrv->variant;      ---> driver data结构体里 有 variant成员， 具体variant可以看下面s3c_fb_variant结构。


...

sfb->bus_clk = clk_get(dev, "lcd"); -->用"lcd"这个名字，去clock文件中找到自己的bus clock

...

clk_enable(sfb->bus_clk); ---> bus clock有什么用，我还不太清楚


...

if (!sfb->variant.has_clksel) {
sfb->lcd_clk = clk_get(dev, "sclk_fimd"); --> 如果driver data里没定义 源时钟， 就用“sclk_fimd”此名字去clock文件找到自己的源时钟

...

clk_enable(sfb->lcd_clk);

....

res = platform_get_resource(pdev, IORESOURCE_MEM, 0); --> 获取资源的物理起始地址，终地址，大小，类型等，放在res结构中。实际上是寄存器们的物理起，终地址。


...

sfb->regs_res = request_mem_region(res->start, resource_size(res), dev_name(dev)); ---> 分配内存

...

sfb->regs = ioremap(res->start, resource_size(res)); ----> 内存映射， 将寄存器的访问地址映射到刚才分配的内存上， sfb->regs为起始地址。

... // 中断的请求略

platform_set_drvdata(pdev, sfb); ---> 将sfb 填入pdev->dev->p->driverdata 结构体中
 ...

pd->setup_gpio();                      --> 执行setup_gpio函数，此函数在上面说的 setup_fimd0.c 中定义了。用来配置GPIO端口给FIMD使用。


...

writel(pd->vidcon1, sfb->regs + VIDCON1);             -->设置VIDCON1 寄存器


/* set video clock running at under-run */
 if (sfb->variant.has_fixvclk) {                                  --> run vclk
 reg = readl(sfb->regs + VIDCON1);
 reg &= ~VIDCON1_VCLK_MASK;
 reg |= VIDCON1_VCLK_RUN;
 writel(reg, sfb->regs + VIDCON1);
 }





 for (win = 0; win < fbdrv->variant.nr_windows; win++)
 s3c_fb_clear_win(sfb, win);                                      ---> 将各个window的wincon寄存器清0，VIDOSDxA, VIDOSDxB, VIDOSDxC清0，禁止update各个window的shadow


/* initialise colour key controls */

 for (win = 0; win < (fbdrv->variant.nr_windows - 1); win++) {

 void __iomem *regs = sfb->regs + sfb->variant.keycon;
 regs += (win * 8);
 writel(0xffffff, regs + WKEYCON0);
 writel(0xffffff, regs + WKEYCON1);
 }


/* we have the register setup, start allocating framebuffers */
default_win = sfb->pdata->default_win;              ---> platform data 在板文件中定义了

for (i = 0; i < fbdrv->variant.nr_windows; i++) {
 win = i;
 if (i == 0)
 win = default_win;
 if (i == default_win)
 win = 0;

if (!pd->win[win])
 continue;

if (!pd->win[win]->win_mode.pixclock)-----> 像素时钟
 s3c_fb_missing_pixclock(&pd->win[win]->win_mode);----->如果像素时钟没预先定义，则由预先设定的刷新率和LCD参数来计算像素时钟

ret = s3c_fb_probe_win(sfb, win, fbdrv->win[win], &sfb->windows[win]);       ----->分配 及 注册framebuffer的重要函数，下面会详细说
 if (ret < 0) {
 dev_err(dev, "failed to create window %d\n", win);
 for (; win >= 0; win--)
 s3c_fb_release_win(sfb, sfb->windows[win]);                     ----> 注册不成功的话就释放之前注册成功过的window
 goto err_irq;
 }
 }


}

...

platform_set_drvdata(pdev, sfb);---> 再一次将sfb 填入pdev->dev->p->driverdata 结构体中，之前曾经这样操作过一次，现在再来一次，是因为sfb里的数据更新了很多
        ...

#ifdef CONFIG_HAS_EARLYSUSPEND--> 如果有定义earlysuspend的话， 则注册early suspend函数
sfb->early_suspend.suspend = s3c_fb_early_suspend;
sfb->early_suspend.resume = s3c_fb_late_resume;
sfb->early_suspend.level = EARLY_SUSPEND_LEVEL_DISABLE_FB;
register_early_suspend(&sfb->early_suspend);
#endif
return 0;
  ...

还有一些错训处理在此略过

}  ---- > probe函数完成

static int __devinit s3c_fb_probe(struct platform_device *pdev)
 {
 const struct platform_device_id *platid;                    -------> 因为一个驱动要适合很多版本的设备，每个版本的设备的设置 参数都不一样，所以要用到platid来选择哪个版本的设备，像“s5pv210-fb”, "s3c2443-fb"..., 这些就是platid(也在s3c-fb.c中定义了)， 也表明了，这个驱动能适合于这些设备。
 struct s3c_fb_driverdata *fbdrv;                         ----> driver data
 struct device *dev = &pdev->dev;
 struct s3c_fb_platdata *pd;                             ----> platform data
 struct s3c_fb *sfb;                                   -----> 一个最重要的数据结据， 它代表了一个显示控制器，显示控制器的所有东东都放在这里了。但这里把它做成一个局部变量了。
 struct resource *res;                              -----> 资源
 int win;
 int default_win;
 ...
 
 platid = platform_get_device_id(pdev);  ----> 从platform device 里 的id_entry 变量中获取platid，由一个宏实现
 
 fbdrv = (struct s3c_fb_driverdata *)platid->driver_data;    ---> 获取platid对应的driver data，driver data在s3c-fb.c中定义，主要是一定设置参数
 
...
 
 pd = pdev->dev.platform_data;  --> 获取platform data，它在板文件中定义，这个data里包含了关于显示控制器的数据，也包含了win的数据。
 

...
 
 sfb = kzalloc(sizeof(struct s3c_fb), GFP_KERNEL);         ------> 给这个最重要的结构分配内存空间
 

...
 
 sfb->dev = dev;                      ---> 向sfb 填入 显示控制器的 device 结构体
 sfb->pdata = pd;                   ---> 向sfb 填入 显示控制器的 platform data 结构体
 sfb->variant = fbdrv->variant;      ---> driver data结构体里 有 variant成员， 具体variant可以看下面s3c_fb_variant结构。
 

...
 
sfb->bus_clk = clk_get(dev, "lcd"); -->用"lcd"这个名字，去clock文件中找到自己的bus clock
 
...
 
clk_enable(sfb->bus_clk); ---> bus clock有什么用，我还不太清楚

 
...
 
if (!sfb->variant.has_clksel) {
sfb->lcd_clk = clk_get(dev, "sclk_fimd"); --> 如果driver data里没定义 源时钟， 就用“sclk_fimd”此名字去clock文件找到自己的源时钟
 
...
 
clk_enable(sfb->lcd_clk);
 
....
 
res = platform_get_resource(pdev, IORESOURCE_MEM, 0); --> 获取资源的物理起始地址，终地址，大小，类型等，放在res结构中。实际上是寄存器们的物理起，终地址。

 
...
 
sfb->regs_res = request_mem_region(res->start, resource_size(res), dev_name(dev)); ---> 分配内存
 
...
 
sfb->regs = ioremap(res->start, resource_size(res)); ----> 内存映射， 将寄存器的访问地址映射到刚才分配的内存上， sfb->regs为起始地址。
 
... // 中断的请求略
 
platform_set_drvdata(pdev, sfb); ---> 将sfb 填入pdev->dev->p->driverdata 结构体中
 ...
 
pd->setup_gpio();                      --> 执行setup_gpio函数，此函数在上面说的 setup_fimd0.c 中定义了。用来配置GPIO端口给FIMD使用。
 

...
 
writel(pd->vidcon1, sfb->regs + VIDCON1);             -->设置VIDCON1 寄存器
 

/* set video clock running at under-run */     
 if (sfb->variant.has_fixvclk) {                                  --> run vclk
 reg = readl(sfb->regs + VIDCON1);
 reg &= ~VIDCON1_VCLK_MASK;
 reg |= VIDCON1_VCLK_RUN;
 writel(reg, sfb->regs + VIDCON1);
 }
 




 for (win = 0; win < fbdrv->variant.nr_windows; win++)
 s3c_fb_clear_win(sfb, win);                                      ---> 将各个window的wincon寄存器清0，VIDOSDxA, VIDOSDxB, VIDOSDxC清0，禁止update各个window的shadow
 

/* initialise colour key controls */
 
 for (win = 0; win < (fbdrv->variant.nr_windows - 1); win++) {
 
 void __iomem *regs = sfb->regs + sfb->variant.keycon;
 regs += (win * 8);
 writel(0xffffff, regs + WKEYCON0);
 writel(0xffffff, regs + WKEYCON1);
 }
 

/* we have the register setup, start allocating framebuffers */
default_win = sfb->pdata->default_win;              ---> platform data 在板文件中定义了
 
for (i = 0; i < fbdrv->variant.nr_windows; i++) {
 win = i;
 if (i == 0)
 win = default_win;
 if (i == default_win)
 win = 0;
 
if (!pd->win[win])
 continue;
 
if (!pd->win[win]->win_mode.pixclock)-----> 像素时钟
 s3c_fb_missing_pixclock(&pd->win[win]->win_mode);----->如果像素时钟没预先定义，则由预先设定的刷新率和LCD参数来计算像素时钟
 
ret = s3c_fb_probe_win(sfb, win, fbdrv->win[win], &sfb->windows[win]);       ----->分配 及 注册framebuffer的重要函数，下面会详细说
 if (ret < 0) {
 dev_err(dev, "failed to create window %d\n", win);
 for (; win >= 0; win--)
 s3c_fb_release_win(sfb, sfb->windows[win]);                     ----> 注册不成功的话就释放之前注册成功过的window
 goto err_irq;
 }
 }
 

}
 
...
 
platform_set_drvdata(pdev, sfb);---> 再一次将sfb 填入pdev->dev->p->driverdata 结构体中，之前曾经这样操作过一次，现在再来一次，是因为sfb里的数据更新了很多
        ...
 
#ifdef CONFIG_HAS_EARLYSUSPEND--> 如果有定义earlysuspend的话， 则注册early suspend函数
sfb->early_suspend.suspend = s3c_fb_early_suspend;
sfb->early_suspend.resume = s3c_fb_late_resume;
sfb->early_suspend.level = EARLY_SUSPEND_LEVEL_DISABLE_FB;
register_early_suspend(&sfb->early_suspend);
#endif
return 0;
  ...
 
还有一些错训处理在此略过
 
}  ---- > probe函数完成

************************************************ s3c_fb_probe_win() *************************************************************

static int __devinit s3c_fb_probe_win(struct s3c_fb *sfb, unsigned int win_no,           --->将显示控制器的结构体作为参数传进来，它有寄存器起始地址等丰富信息；还将win的号码也作为参数传进来
      struct s3c_fb_win_variant *variant,            ----> driver data中win的部份, 它是由fbdrv->win[win]作参数传过来的。
      struct s3c_fb_win **res)       ---> per window private data for each framebuffer，它里面含有指向FBI(fb_info)结构体的针指
 {
 struct fb_var_screeninfo *var;
 struct fb_videomode *initmode;
 struct s3c_fb_pd_win *windata;    -->per window setup data,  也就是platform data中win的部份
 struct s3c_fb_win *win;
 struct fb_info *fbinfo;
 int palette_size;
 int ret;


init_waitqueue_head(&sfb->vsync_info.wait);  ---> 初始化等待队列头

palette_size = variant->palette_sz * 4;         ---> 调色板大小 ， 这方面内容我还不了解，为什么乘以4？


fbinfo = framebuffer_alloc(sizeof(struct s3c_fb_win) +  palette_size * sizeof(u32), sfb->dev);   ---> 重头戏来了， 分配fb_info结构体，返回一个fb_info结构体地址，这个结构体现在没什么内容，只赋值了par(win的起始地址)和device (父设备)两个变量，

windata = sfb->pdata->win[win_no];         --->windata指向 platform data中win的部份
initmode = &windata->win_mode;

...

win = fbinfo->par;
*res = win;         --->par就是win的起始地址，现在把起始地址给*res，那么*res就是指向s3c_fb_win的指针
var = &fbinfo->var;         ---> 现在fbinfo->var还是空的， 只是将地址给var而已
win->variant = *variant;         --->将win的参数填进win->variant里
win->fbinfo = fbinfo;         ---让win->fbinfo指向这个FBI结构实体
win->parent = sfb;         ---win的parent是显示控制器，所以它指向sfb结构体>
win->windata = windata;        --->让win->windata指向 platform data中win的部分
win->index = win_no;

win->palette_buffer = (u32 *)(win + 1);       --->这个也不太理解?

ret = s3c_fb_alloc_memory(sfb, win);    ----> 下面详解

...

/* setup the r/b/g positions for the window's palette */                --->设置调色板， 未理解
 if (win->variant.palette_16bpp) {
 /* Set RGB 5:6:5 as default */
 win->palette.r.offset = 11;
 win->palette.r.length = 5;
 win->palette.g.offset = 5;
 win->palette.g.length = 6;
 win->palette.b.offset = 0;
 win->palette.b.length = 5;


} else {
 /* Set 8bpp or 8bpp and 1bit alpha */
 win->palette.r.offset = 16;
 win->palette.r.length = 8;
 win->palette.g.offset = 8;
 win->palette.g.length = 8;
 win->palette.b.offset = 0;
 win->palette.b.length = 8;
 }


/* setup the initial video mode from the window */
 fb_videomode_to_var(&fbinfo->var, initmode);      --> 给FBI填上各个参数，此函数详见appendix

fbinfo->fix.type
= FB_TYPE_PACKED_PIXELS;
fbinfo->fix.accel= FB_ACCEL_NONE;
fbinfo->var.activate= FB_ACTIVATE_NOW;
fbinfo->var.vmode= FB_VMODE_NONINTERLACED;
fbinfo->var.bits_per_pixel = windata->default_bpp;
fbinfo->var.width= windata->width;
fbinfo->var.height= windata->height;
fbinfo->fbops
= &s3c_fb_ops;    ---->对framebuffer的操作， 详见appendix
fbinfo->flags
= FBINFO_FLAG_DEFAULT;
fbinfo->pseudo_palette  = &win->pseudo_palette;

/* prepare to actually start the framebuffer */
 ret = s3c_fb_check_var(&fbinfo->var, fbinfo);    -->检查可变参数 Framebuffer layer call to verify the given information and allow us to update various information depending on the hardware capabilities.


...

ret = fb_alloc_cmap(&fbinfo->cmap, win->variant.palette_sz, 1);

if (ret == 0)
 fb_set_cmap(&fbinfo->cmap, fbinfo);
 else
 dev_err(sfb->dev, "failed to allocate fb cmap\n");


s3c_fb_set_par(fbinfo);

...

ret = register_framebuffer(fbinfo);

...

return 0;

} s3c_fb_probe_win结束

static int __devinit s3c_fb_probe_win(struct s3c_fb *sfb, unsigned int win_no,           --->将显示控制器的结构体作为参数传进来，它有寄存器起始地址等丰富信息；还将win的号码也作为参数传进来
      struct s3c_fb_win_variant *variant,            ----> driver data中win的部份, 它是由fbdrv->win[win]作参数传过来的。
      struct s3c_fb_win **res)       ---> per window private data for each framebuffer，它里面含有指向FBI(fb_info)结构体的针指
 {
 struct fb_var_screeninfo *var;
 struct fb_videomode *initmode;
 struct s3c_fb_pd_win *windata;    -->per window setup data,  也就是platform data中win的部份
 struct s3c_fb_win *win;
 struct fb_info *fbinfo;
 int palette_size;
 int ret;
 

init_waitqueue_head(&sfb->vsync_info.wait);  ---> 初始化等待队列头
 
palette_size = variant->palette_sz * 4;         ---> 调色板大小 ， 这方面内容我还不了解，为什么乘以4？
 

fbinfo = framebuffer_alloc(sizeof(struct s3c_fb_win) +  palette_size * sizeof(u32), sfb->dev);   ---> 重头戏来了， 分配fb_info结构体，返回一个fb_info结构体地址，这个结构体现在没什么内容，只赋值了par(win的起始地址)和device (父设备)两个变量，
 
windata = sfb->pdata->win[win_no];         --->windata指向 platform data中win的部份 
initmode = &windata->win_mode;
 
...
 
win = fbinfo->par;
*res = win;         --->par就是win的起始地址，现在把起始地址给*res，那么*res就是指向s3c_fb_win的指针 
var = &fbinfo->var;         ---> 现在fbinfo->var还是空的， 只是将地址给var而已 
win->variant = *variant;         --->将win的参数填进win->variant里 
win->fbinfo = fbinfo;         ---让win->fbinfo指向这个FBI结构实体 
win->parent = sfb;         ---win的parent是显示控制器，所以它指向sfb结构体> 
win->windata = windata;        --->让win->windata指向 platform data中win的部分 
win->index = win_no; 
      
win->palette_buffer = (u32 *)(win + 1);       --->这个也不太理解?
 
ret = s3c_fb_alloc_memory(sfb, win);    ----> 下面详解
 
...
 
/* setup the r/b/g positions for the window's palette */                --->设置调色板， 未理解
 if (win->variant.palette_16bpp) {
 /* Set RGB 5:6:5 as default */
 win->palette.r.offset = 11;
 win->palette.r.length = 5;
 win->palette.g.offset = 5;
 win->palette.g.length = 6;
 win->palette.b.offset = 0;
 win->palette.b.length = 5;
 

} else {
 /* Set 8bpp or 8bpp and 1bit alpha */
 win->palette.r.offset = 16;
 win->palette.r.length = 8;
 win->palette.g.offset = 8;
 win->palette.g.length = 8;
 win->palette.b.offset = 0;
 win->palette.b.length = 8;
 }
 

/* setup the initial video mode from the window */
 fb_videomode_to_var(&fbinfo->var, initmode);      --> 给FBI填上各个参数，此函数详见appendix
 
fbinfo->fix.type 
= FB_TYPE_PACKED_PIXELS;
fbinfo->fix.accel= FB_ACCEL_NONE;
fbinfo->var.activate= FB_ACTIVATE_NOW;
fbinfo->var.vmode= FB_VMODE_NONINTERLACED;
fbinfo->var.bits_per_pixel = windata->default_bpp;
fbinfo->var.width= windata->width;
fbinfo->var.height= windata->height;
fbinfo->fbops 
= &s3c_fb_ops;    ---->对framebuffer的操作， 详见appendix
fbinfo->flags 
= FBINFO_FLAG_DEFAULT;
fbinfo->pseudo_palette  = &win->pseudo_palette; 
 
/* prepare to actually start the framebuffer */
 ret = s3c_fb_check_var(&fbinfo->var, fbinfo);    -->检查可变参数 Framebuffer layer call to verify the given information and allow us to update various information depending on the hardware capabilities.
 

...
 
ret = fb_alloc_cmap(&fbinfo->cmap, win->variant.palette_sz, 1);
 
if (ret == 0)
 fb_set_cmap(&fbinfo->cmap, fbinfo);
 else
 dev_err(sfb->dev, "failed to allocate fb cmap\n");
 

s3c_fb_set_par(fbinfo);
 
...
 
ret = register_framebuffer(fbinfo);
 
...
 
return 0;
 
} s3c_fb_probe_win结束

************************************************ s3c_fb_alloc_memory() ************************************************

static int __devinit s3c_fb_alloc_memory(struct s3c_fb *sfb,
 struct s3c_fb_win *win)
 {
 struct s3c_fb_pd_win *windata = win->windata;  ---> platform data中win的部分
 unsigned int real_size, virt_size, size;
 struct fb_info *fbi = win->fbinfo;     ---> 让fbi指向FBI结构体

dma_addr_t map_dma;


     ...

real_size = windata->win_mode.xres * windata->win_mode.yres;
virt_size = windata->virtual_x * windata->virtual_y;    ---> 虚拟size

size = (real_size > virt_size) ? real_size : virt_size; 一张framebuffer的大小，是按虚拟分辨率和实际分辨率两者中较大的来算的
size *= (windata->max_bpp > 16) ? 32 : windata->max_bpp;
size /= 8;

fbi->fix.smem_len = size;-----> 要分配的内存大小，
 size = PAGE_ALIGN(size);    ---- 页对齐


... 关于CMA 与ION部分省略

fbi->screen_base = dma_alloc_writecombine(sfb->dev, size,  &map_dma, GFP_KERNEL);   -->分配framebuffer的内存

memset(fbi->screen_base, 0x0, size);    -->将framebuffer的内存清空为0
 fbi->fix.smem_start = map_dma;
 return 0;


}  ---->结束

static int __devinit s3c_fb_alloc_memory(struct s3c_fb *sfb,
 struct s3c_fb_win *win)
 {
 struct s3c_fb_pd_win *windata = win->windata;  ---> platform data中win的部分
 unsigned int real_size, virt_size, size;
 struct fb_info *fbi = win->fbinfo;     ---> 让fbi指向FBI结构体
 
dma_addr_t map_dma;
 

     ...
 
real_size = windata->win_mode.xres * windata->win_mode.yres;
virt_size = windata->virtual_x * windata->virtual_y;    ---> 虚拟size
 
size = (real_size > virt_size) ? real_size : virt_size; 一张framebuffer的大小，是按虚拟分辨率和实际分辨率两者中较大的来算的
size *= (windata->max_bpp > 16) ? 32 : windata->max_bpp;
size /= 8; 
 
fbi->fix.smem_len = size;-----> 要分配的内存大小，
 size = PAGE_ALIGN(size);    ---- 页对齐
 

... 关于CMA 与ION部分省略
 
fbi->screen_base = dma_alloc_writecombine(sfb->dev, size,  &map_dma, GFP_KERNEL);   -->分配framebuffer的内存
 
memset(fbi->screen_base, 0x0, size);    -->将framebuffer的内存清空为0
 fbi->fix.smem_start = map_dma;
 return 0;
 

}  ---->结束

*********************************************************Appendix******************************************************

struct s3c_fb_variant {
 unsigned int  is_2443:1;
 unsigned shortnr_windows;
 unsigned int  vidtcon;
 unsigned shortwincon;
 unsigned shortwinmap;
 unsigned shortkeycon;
 unsigned shortbuf_start;
 unsigned shortbuf_end;
 unsigned shortbuf_size;
 unsigned shortosd;
 unsigned shortosd_stride;
 unsigned shortpalette[S3C_FB_MAX_WIN];


unsigned int  has_prtcon:1;
 unsigned int  has_shadowcon:1;
 unsigned int  has_blendcon:1;
 unsigned int  has_alphacon:1;
 unsigned int  has_clksel:1;
 unsigned int  has_fixvclk:1;


}




/**
  * fb_videomode_to_var - convert fb_videomode to fb_var_screeninfo
  * @var: pointer to struct fb_var_screeninfo
  * @mode: pointer to struct fb_videomode
  */
 void fb_videomode_to_var(struct fb_var_screeninfo *var,
 const struct fb_videomode *mode)
 {
 var->xres = mode->xres;
 var->yres = mode->yres;
 var->xres_virtual = mode->xres;
 var->yres_virtual = mode->yres;
 var->xoffset = 0;
 var->yoffset = 0;
 var->pixclock = mode->pixclock;
 var->left_margin = mode->left_margin;
 var->right_margin = mode->right_margin;
 var->upper_margin = mode->upper_margin;
 var->lower_margin = mode->lower_margin;
 var->hsync_len = mode->hsync_len;
 var->vsync_len = mode->vsync_len;
 var->sync = mode->sync;
 var->vmode = mode->vmode & FB_VMODE_MASK;
 }





static struct fb_ops s3c_fb_ops = {
 .owner  = THIS_MODULE,
 .fb_open  = s3c_fb_open,
 .fb_release  = s3c_fb_release,
 .fb_check_var  = s3c_fb_check_var,
 .fb_set_par  = s3c_fb_set_par,
 .fb_blank  = s3c_fb_blank,
 .fb_setcolreg  = s3c_fb_setcolreg,
 .fb_fillrect  = cfb_fillrect,
 .fb_copyarea  = cfb_copyarea,
 .fb_imageblit  = cfb_imageblit,
 .fb_pan_display= s3c_fb_pan_display,
 .fb_ioctl  = s3c_fb_ioctl,
 };





/**
  * struct s3c_fb_win - per window private data for each framebuffer.
  * @windata: The platform data supplied for the window configuration.
  * @parent: The hardware that this window is part of.
  * @fbinfo: Pointer pack to the framebuffer info for this window.
  * @varint: The variant information for this window.
  * @palette_buffer: Buffer/cache to hold palette entries.
  * @pseudo_palette: For use in TRUECOLOUR modes for entries 0..15/
  * @index: The window number of this window.
  * @palette: The bitfields for changing r/g/b into a hardware palette entry.
  */
 struct s3c_fb_win {
 struct s3c_fb_pd_win*windata;
 struct s3c_fb  *parent;
 struct fb_info*fbinfo;
 struct s3c_fb_palettepalette;
 struct s3c_fb_win_variant variant;


u32  *palette_buffer;
 u32  pseudo_palette[16];
 unsigned int  index;
 #ifdef CONFIG_ION_EXYNOS
 struct ion_handle *fb_ion_handle;
 #endif
 };

struct s3c_fb_variant {
 unsigned int  is_2443:1;
 unsigned shortnr_windows;
 unsigned int  vidtcon;
 unsigned shortwincon;
 unsigned shortwinmap;
 unsigned shortkeycon;
 unsigned shortbuf_start;
 unsigned shortbuf_end;
 unsigned shortbuf_size;
 unsigned shortosd;
 unsigned shortosd_stride;
 unsigned shortpalette[S3C_FB_MAX_WIN];
 

unsigned int  has_prtcon:1;
 unsigned int  has_shadowcon:1;
 unsigned int  has_blendcon:1;
 unsigned int  has_alphacon:1;
 unsigned int  has_clksel:1;
 unsigned int  has_fixvclk:1;
 

}
 



/**
  * fb_videomode_to_var - convert fb_videomode to fb_var_screeninfo
  * @var: pointer to struct fb_var_screeninfo
  * @mode: pointer to struct fb_videomode
  */
 void fb_videomode_to_var(struct fb_var_screeninfo *var,
 const struct fb_videomode *mode)
 {
 var->xres = mode->xres;
 var->yres = mode->yres;
 var->xres_virtual = mode->xres;
 var->yres_virtual = mode->yres;
 var->xoffset = 0;
 var->yoffset = 0;
 var->pixclock = mode->pixclock;
 var->left_margin = mode->left_margin;
 var->right_margin = mode->right_margin;
 var->upper_margin = mode->upper_margin;
 var->lower_margin = mode->lower_margin;
 var->hsync_len = mode->hsync_len;
 var->vsync_len = mode->vsync_len;
 var->sync = mode->sync;
 var->vmode = mode->vmode & FB_VMODE_MASK;
 }
 




static struct fb_ops s3c_fb_ops = {
 .owner  = THIS_MODULE,
 .fb_open  = s3c_fb_open,
 .fb_release  = s3c_fb_release,
 .fb_check_var  = s3c_fb_check_var,
 .fb_set_par  = s3c_fb_set_par,
 .fb_blank  = s3c_fb_blank,
 .fb_setcolreg  = s3c_fb_setcolreg,
 .fb_fillrect  = cfb_fillrect,
 .fb_copyarea  = cfb_copyarea,
 .fb_imageblit  = cfb_imageblit,
 .fb_pan_display= s3c_fb_pan_display,
 .fb_ioctl  = s3c_fb_ioctl,
 };
 




/**
  * struct s3c_fb_win - per window private data for each framebuffer.
  * @windata: The platform data supplied for the window configuration.
  * @parent: The hardware that this window is part of.
  * @fbinfo: Pointer pack to the framebuffer info for this window.
  * @varint: The variant information for this window.
  * @palette_buffer: Buffer/cache to hold palette entries.
  * @pseudo_palette: For use in TRUECOLOUR modes for entries 0..15/
  * @index: The window number of this window.
  * @palette: The bitfields for changing r/g/b into a hardware palette entry.
  */
 struct s3c_fb_win {
 struct s3c_fb_pd_win*windata;
 struct s3c_fb  *parent;
 struct fb_info*fbinfo;
 struct s3c_fb_palettepalette;
 struct s3c_fb_win_variant variant;
 

u32  *palette_buffer;
 u32  pseudo_palette[16];
 unsigned int  index;
 #ifdef CONFIG_ION_EXYNOS
 struct ion_handle *fb_ion_handle;
 #endif
 };

 转载自：http://blog.csdn.net/lihaoweiV/article/details/6988718