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前言

驱动端实现Linux模拟Framebuffer驱动；应用端采用GTK＋实现多个应用程序通过接口/dev/fbXXX访问Framebuffer.基于该接口,可以在PC电脑Ubuntu系统实现基本的画点，画线等基本的绘图操作．

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一、模拟Framebuffer驱动

1.总体功能

实现一个misc设备,通过文件属性接口接收应用层下达的创建Framebuffer参数创建Framebuffer设备.

2.驱动代码

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/dma-mapping.h>
#include <linux/platform_device.h>#define FB_NUM 4
static struct fb_info *imulate_lcd[FB_NUM]={NULL,NULL,NULL,NULL};
static int pcolor_format=1;
static int pbytes_per_pixel=4;
static int pbits_per_color=8;
static int pwidth=1280;
static int pheight=800;
static int pid=0;
static volatile int current_fb=-1;
static struct miscdevice misc={.minor=255,.name="simulate_fb", 
};
static int simulate_mmap(struct fb_info *fbinfo, struct vm_area_struct *vma)
{if(remap_pfn_range(vma, vma->vm_start, fbinfo->fix.smem_start >>PAGE_SHIFT,vma->vm_end-vma->vm_start, vma->vm_page_prot)){return -EAGAIN;}printk(KERN_INFO "simulate_mmap OK\n");return 0;
}
static struct fb_ops simulate_fbops=
{.owner = THIS_MODULE,.fb_mmap = simulate_mmap
};
static ssize_t simulate_fb_create_show(struct device *dev, struct device_attribute *attr, char *buf)
{printk(KERN_INFO "current_fd=%d\n", current_fb);return sprintf(buf,"%d", current_fb);
}
static ssize_t simulate_fb_create_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{sscanf(buf,"%d %d %d %d %d %d",&pid, &pcolor_format,&pbytes_per_pixel,&pbits_per_color,&pwidth,&pheight);printk(KERN_INFO "id=%d,color_format=%d,bytes_per_pixel=%d,bits_per_pixel=%d,widht=%d,height=%d\n",pid,pcolor_format, pbytes_per_pixel, pbits_per_color,pwidth,pheight);current_fb = -1;if(pid >= FB_NUM || pid < 0 || imulate_lcd[pid] != NULL){printk(KERN_INFO "FB num error.%d\n", pid);return count;}imulate_lcd[pid] = framebuffer_alloc(sizeof(struct fb_info), NULL);sprintf(imulate_lcd[pid]->fix.id,"rrfb%d", pid);imulate_lcd[pid]->fix.smem_len = pwidth*pheight*pbytes_per_pixel;imulate_lcd[pid]->fix.type = FB_TYPE_PACKED_PIXELS;imulate_lcd[pid]->fix.visual = FB_VISUAL_TRUECOLOR;imulate_lcd[pid]->fix.line_length = pwidth*pbytes_per_pixel;imulate_lcd[pid]->var.xres             = pwidth;imulate_lcd[pid]->var.yres             = pheight;imulate_lcd[pid]->var.xres_virtual  = pwidth;imulate_lcd[pid]->var