LCD电子书项目（二）

这篇文章我们讲解display目录，是对LCD显示部分的操作。

该目录下的文件结构如下：

Makefile

<span style="font-size:18px;">obj-y += disp_manager.o
obj-y += fb.o
obj-y += test/</span>

disp_manager.h

<span style="font-size:18px;">#ifndef _DISP_MANAGER_H
#define _DISP_MANAGER_H

typedef struct DispOpr {
char *name;
int iXres;
int iYres;
int iBpp;
int (*DeviceInit)(void);
int (*ShowPixel)(int iPenX, int iPenY, unsigned int dwColor);
int (*CleanScreen)(unsigned int dwBackColor);
struct DispOpr *ptNext;
}T_DispOpr, *PT_DispOpr;

int RegisterDispOpr(PT_DispOpr ptDispOpr);
void ShowDispOpr(void);
int DisplayInit(void);
int FBInit(void);

#endif /* _DISP_MANAGER_H */
</span>

disp_manager.c

<span style="font-size:18px;">#include <config.h>
#include <disp_manager.h>
#include <string.h>

static PT_DispOpr g_ptDispOprHead;

int RegisterDispOpr(PT_DispOpr ptDispOpr)
{
PT_DispOpr ptTmp;

if (!g_ptDispOprHead)
{
g_ptDispOprHead   = ptDispOpr;
ptDispOpr->ptNext = NULL;
}
else
{
ptTmp = g_ptDispOprHead;
while (ptTmp->ptNext)
{
ptTmp = ptTmp->ptNext;
}
ptTmp->ptNext  = ptDispOpr;
ptDispOpr->ptNext = NULL;
}

return 0;
}


void ShowDispOpr(void)
{
int i = 0;
PT_DispOpr ptTmp = g_ptDispOprHead;

while (ptTmp)
{
printf("%02d %s\n", i++, ptTmp->name);
ptTmp = ptTmp->ptNext;
}
}

PT_DispOpr GetDispOpr(char *pcName)
{
PT_DispOpr ptTmp = g_ptDispOprHead;

while (ptTmp)
{
if (strcmp(ptTmp->name, pcName) == 0)
{
return ptTmp;
}
ptTmp = ptTmp->ptNext;
}
return NULL;
}

int DisplayInit(void)
{
int iError;

iError = FBInit();

return iError;
}
</span>

fb.c

<span style="font-size:18px;">#include <config.h>
#include <disp_manager.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/fb.h>
#include <string.h>

static int FBDeviceInit(void);
static int FBShowPixel(int iX, int iY, unsigned int dwColor);
static int FBCleanScreen(unsigned int dwBackColor);


static int g_fd;

static struct fb_var_screeninfo g_tFBVar;
static struct fb_fix_screeninfo g_tFBFix;
static unsigned char *g_pucFBMem;
static unsigned int g_dwScreenSize;

static unsigned int g_dwLineWidth;
static unsigned int g_dwPixelWidth;

static T_DispOpr g_tFBOpr = {
.name        = "fb",
.DeviceInit  = FBDeviceInit,
.ShowPixel   = FBShowPixel,
.CleanScreen = FBCleanScreen,
};

static int FBDeviceInit(void)
{
int ret;

g_fd = open(FB_DEVICE_NAME, O_RDWR);
if (0 > g_fd)
{
DBG_PRINTF("can't open %s\n", FB_DEVICE_NAME);
}

ret = ioctl(g_fd, FBIOGET_VSCREENINFO, &g_tFBVar);
if (ret < 0)
{
DBG_PRINTF("can't get fb's var\n");
return -1;
}

ret = ioctl(g_fd, FBIOGET_FSCREENINFO, &g_tFBFix);
if (ret < 0)
{
DBG_PRINTF("can't get fb's fix\n");
return -1;
}

g_dwScreenSize = g_tFBVar.xres * g_tFBVar.yres * g_tFBVar.bits_per_pixel / 8;
g_pucFBMem = (unsigned char *)mmap(NULL , g_dwScreenSize, PROT_READ | PROT_WRITE, MAP_SHARED, g_fd, 0);
if (0 > g_pucFBMem)
{
DBG_PRINTF("can't mmap\n");
return -1;
}

g_tFBOpr.iXres       = g_tFBVar.xres;
g_tFBOpr.iYres       = g_tFBVar.yres;
g_tFBOpr.iBpp        = g_tFBVar.bits_per_pixel;

g_dwLineWidth  = g_tFBVar.xres * g_tFBVar.bits_per_pixel / 8;
g_dwPixelWidth = g_tFBVar.bits_per_pixel / 8;

return 0;
}


static int FBShowPixel(int iX, int iY, unsigned int dwColor)
{
unsigned char *pucFB;
unsigned short *pwFB16bpp;
unsigned int *pdwFB32bpp;
unsigned short wColor16bpp; /* 565 */
int iRed;
int iGreen;
int iBlue;

if ((iX >= g_tFBVar.xres) || (iY >= g_tFBVar.yres))
{
DBG_PRINTF("out of region\n");
return -1;
}

pucFB      = g_pucFBMem + g_dwLineWidth * iY + g_dwPixelWidth * iX;
pwFB16bpp  = (unsigned short *)pucFB;
pdwFB32bpp = (unsigned int *)pucFB;

switch (g_tFBVar.bits_per_pixel)
{
case 8:
{
*pucFB = (unsigned char)dwColor;
break;
}
case 16:
{
iRed   = (dwColor >> (16+3)) & 0x1f;
iGreen = (dwColor >> (8+2)) & 0x3f;
iBlue  = (dwColor >> 3) & 0x1f;
wColor16bpp = (iRed << 11) | (iGreen << 5) | iBlue;
*pwFB16bpp= wColor16bpp;
break;
}
case 32:
{
*pdwFB32bpp = dwColor;
break;
}
default :
{
DBG_PRINTF("can't support %d bpp\n", g_tFBVar.bits_per_pixel);
return -1;
}
}

return 0;
}

static int FBCleanScreen(unsigned int dwBackColor)
{
unsigned char *pucFB;
unsigned short *pwFB16bpp;
unsigned int *pdwFB32bpp;
unsigned short wColor16bpp; /* 565 */
int iRed;
int iGreen;
int iBlue;
int i = 0;

pucFB      = g_pucFBMem;
pwFB16bpp  = (unsigned short *)pucFB;
pdwFB32bpp = (unsigned int *)pucFB;

switch (g_tFBVar.bits_per_pixel)
{
case 8:
{
memset(g_pucFBMem, dwBackColor, g_dwScreenSize);
break;
}
case 16:
{
iRed   = (dwBackColor >> (16+3)) & 0x1f;
iGreen = (dwBackColor >> (8+2)) & 0x3f;
iBlue  = (dwBackColor >> 3) & 0x1f;
wColor16bpp = (iRed << 11) | (iGreen << 5) | iBlue;
while (i < g_dwScreenSize)
{
*pwFB16bpp= wColor16bpp;
pwFB16bpp++;
i += 2;
}
break;
}
case 32:
{
while (i < g_dwScreenSize)
{
*pdwFB32bpp= dwBackColor;
pdwFB32bpp++;
i += 4;
}
break;
}
default :
{
DBG_PRINTF("can't support %d bpp\n", g_tFBVar.bits_per_pixel);
return -1;
}
}

return 0;
}

int FBInit(void)
{
return RegisterDispOpr(&g_tFBOpr);
}
</span>

这部分代码非常简单，仔细阅读就能够自己看懂了。