这一篇博文承接上一篇博文“系统lcd驱动（－）”（/Ian22l/article/details/105927936），这篇博文讲的是mtk的lcd驱动一部分。
上一篇讲到在移植或者调试的时候需要填充fb_info对象信息并且进行register_framebuffer进行注册。那么mtk的lcd驱动便是实现这一部分的逻辑。首先从mtkfb_probe进行底层硬件lcd驱动的加载。如下：
代码路径：
drivers/misc/mediatek/video/xxx/videox/mtkfb.c(其中xxx代表某个具体平台，例如mt3561)
static int mtkfb_probe(struct platform_device *pdev){struct mtkfb_device *fbdev = NULL;struct fb_info *fbi;............/*申请一块fb_info类型的内存*/fbi = framebuffer_alloc(sizeof(struct mtkfb_device), &(pdev->dev));if (!fbi) {DISPERR("unable to allocate memory for device info\n");r = -ENOMEM;goto cleanup;}mtkfb_fbi = fbi;fbdev = (struct mtkfb_device *)fbi->par;fbdev->fb_info = fbi;fbdev->dev = &(pdev->dev);dev_set_drvdata(&(pdev->dev), fbdev);............/*lcd控制器以及lcm模组的初始化*/primary_display_init(mtkfb_find_lcm_driver(), lcd_fps, is_lcm_inited);............/*初始化fb_info*/r = mtkfb_fbinfo_init(fbi);if (r) {DISPERR("mtkfb_fbinfo_init fail, r = %d\n", r);goto cleanup;}............/*注册fb_info结构体fbi*/r = register_framebuffer(fbi);if (r != 0) {DISPERR("register_framebuffer failed\n");goto cleanup;}DISPMSG("register_framebuffer done\n");......return r;}
mtk的驱动其实可以分为两条线，一个是初始化fb_info结构体，另外一个是lcm模组的一些初始化。这里我们先说fb_info的初始化，后续会说lcm模组的初始化。
一：fb_info结构体的初始化以及注册
从上面的代码看出，fb_info结构体的初始化主要是通过mtkfb_fbinfo_init进行fb_info对象的填充，然后再通过r = register_framebuffer(fbi);进行注册。这正是我们上一篇博文的结尾所提到的内容。这里我们看下fb_info的初始化主要初始化的内容是什么。
mtkfb_fbinfo_init代码主要内容：
static int mtkfb_fbinfo_init(struct fb_info *info){struct mtkfb_device *fbdev = (struct mtkfb_device *)info->par;struct fb_var_screeninfo var;int r = 0;DISPFUNC();ASSERT(fbdev->fb_va_base);/*初始化操作集合*/info->fbops = &mtkfb_ops;info->flags = FBINFO_FLAG_DEFAULT;info->screen_base = (char *)fbdev->fb_va_base;info->screen_size = fbdev->fb_size_in_byte;info->pseudo_palette = fbdev->pseudo_palette;r = fb_alloc_cmap(&info->cmap, 32, 0);if (r != 0)DISPERR("unable to allocate color map memory\n");/* setup the initial video mode (RGB565) */memset(&var, 0, sizeof(var));/*初始化可变参数fb_var_screeninfo，例如分辨率*/var.xres = MTK_FB_XRES;var.yres = MTK_FB_YRES;var.xres_virtual = MTK_FB_XRESV;var.yres_virtual = MTK_FB_YRESV;DISPMSG("mtkfb_fbinfo_init var.xres=%d,var.yres=%d,var.xres_virtual=%d,var.yres_virtual=%d\n",var.xres, var.yres, var.xres_virtual, var.yres_virtual);/* use 32 bit framebuffer as default */var.bits_per_pixel = 32;var.transp.offset = 24;var.red.length = 8;/*初始化颜色位域*/#if 0var.red.offset = 16;var.red.length = 8;var.green.offset = 8;var.green.length = 8;var.blue.offset = 0;var.blue.length = 8;#elsevar.red.offset = 0;var.red.length = 8;var.green.offset = 8;var.green.length = 8;var.blue.offset = 16;var.blue.length = 8;#endifvar.width = DISP_GetActiveWidth();var.height = DISP_GetActiveHeight();var.activate = FB_ACTIVATE_NOW;r = mtkfb_check_var(&var, info);if (r != 0)DISPERR("failed to mtkfb_check_var\n");/*将已经初始化好的fb_var_screeninfo对象赋值给info中的var*/info->var = var;/*初始化fb_fix_screeninfo*/r = mtkfb_set_par(info);if (r != 0)DISPERR("failed to mtkfb_set_par\n");MSG_FUNC_LEAVE();return r;}
fb_info的初始化内核主要是对fb_var_screeninfo以及fb_fix_screeninfo，info->fbops的初始化。
（１）其中fb_var_screeninfo的初始化主要进行分辨率，颜色位域等初始化。
（２）nfo->fbops的初始化：
static struct fb_ops mtkfb_ops = {.owner = THIS_MODULE,.fb_open = mtkfb_open,.fb_release = mtkfb_release,.fb_setcolreg = mtkfb_setcolreg,.fb_pan_display = mtkfb_pan_display_proxy,.fb_fillrect = cfb_fillrect,.fb_copyarea = cfb_copyarea,.fb_imageblit = cfb_imageblit,.fb_cursor = mtkfb_soft_cursor,.fb_check_var = mtkfb_check_var,.fb_set_par = mtkfb_set_par,.fb_ioctl = mtkfb_ioctl,#ifdef CONFIG_COMPAT.fb_compat_ioctl = mtkfb_compat_ioctl,#endif#if defined(CONFIG_PM_AUTOSLEEP).fb_blank = mtkfb_blank,#endif};
（３）fb_fix_screeninfo初始化：
/* Switch to a new mode. The parameters for it has been check already by* mtkfb_check_var.*/static int mtkfb_set_par(struct fb_info *fbi){struct fb_var_screeninfo *var = &fbi->var;struct mtkfb_device *fbdev = (struct mtkfb_device *)fbi->par;struct fb_overlay_layer fb_layer;u32 bpp = var->bits_per_pixel;struct disp_session_input_config *session_input;struct disp_input_config *input;/* DISPFUNC(); */memset(&fb_layer, 0, sizeof(struct fb_overlay_layer));switch (bpp) {case 16:fb_layer.src_fmt = MTK_FB_FORMAT_RGB565;fb_layer.src_use_color_key = 1;fb_layer.src_color_key = 0xFF000000;break;case 24:fb_layer.src_use_color_key = 1;fb_layer.src_fmt = (var->blue.offset == 0) ?MTK_FB_FORMAT_RGB888 : MTK_FB_FORMAT_BGR888;fb_layer.src_color_key = 0xFF000000;break;case 32:fb_layer.src_use_color_key = 0;DISPDBG("set_par,var->blue.offset=%d\n", var->blue.offset);fb_layer.src_fmt = (var->blue.offset == 0) ?MTK_FB_FORMAT_ARGB8888 : MTK_FB_FORMAT_BGRA8888;fb_layer.src_color_key = 0;break;default:fb_layer.src_fmt = MTK_FB_FORMAT_UNKNOWN;DISPWARN("[%s]unsupported bpp: %d", __func__, bpp);return -1;}//初始化fb_fix_screeninfoset_fb_fix(fbdev);}
static void set_fb_fix(struct mtkfb_device *fbdev){struct fb_info *fbi = fbdev->fb_info;struct fb_fix_screeninfo *fix = &fbi->fix;struct fb_var_screeninfo *var = &fbi->var;struct fb_ops *fbops = fbi->fbops;strncpy(fix->id, MTKFB_DRIVER, sizeof(fix->id));fix->type = FB_TYPE_PACKED_PIXELS;switch (var->bits_per_pixel) {case 16:case 24:case 32:fix->visual = FB_VISUAL_TRUECOLOR;break;case 1:case 2:case 4:case 8:fix->visual = FB_VISUAL_PSEUDOCOLOR;break;default:DISPERR("set fb fix fail,bits per pixel=%d\n",var->bits_per_pixel);return;}fix->accel = FB_ACCEL_NONE;fix->line_length = ALIGN_TO(var->xres_virtual, MTK_FB_ALIGNMENT) *var->bits_per_pixel / 8;fix->smem_len = fbdev->fb_size_in_byte;fix->smem_start = fbdev->fb_pa_base;fix->xpanstep = 0;fix->ypanstep = 1;fbops->fb_fillrect = cfb_fillrect;fbops->fb_copyarea = cfb_copyarea;fbops->fb_imageblit = cfb_imageblit;}
