Linux-2.6.38的LCD驱动分析（四）

Linux-2.6.38的LCD驱动分析（四）

参考自：http://blog.chinaunix.net/uid-11114210-id-2907026.html

四、s3cfb_ops变量详解

        在上面的文字中，较为详细的解释了platform device相关的代码，通过上面的代码的执行，一个platform设备（framebuffer被当作了platform设备）就加载到内核中去了。就像一个PCI的网卡被加入到内核一样，不同的是PCI的网卡占用的是PCI总线，内核会直接支持它。而对于platform设备需要用上面软件的方法加载到内核，同PCI网卡一样，设备需要驱动程序，刚才只是将platform设备注册到内核中，现在它还需要驱动程序，本节中就来看看这些驱动。

4.1  struct fb_ops and s3cfb_ops

/*
 * Frame buffer operations
 *
 * LOCKING NOTE: those functions must _ALL_ be called with the console
 * semaphore held, this is the only suitable locking mechanism we have
 * in 2.6. Some may be called at interrupt time at this point though.
 *
 * The exception to this is the debug related hooks.  Putting the fb
 * into a debug state (e.g. flipping to the kernel console) and restoring
 * it must be done in a lock-free manner, so low level drivers should
 * keep track of the initial console (if applicable) and may need to
 * perform direct, unlocked hardware writes in these hooks.
 */
struct fb_ops {
/* open/release and usage marking */
struct module *owner;
int (*fb_open)(struct fb_info *info, int user);
int (*fb_release)(struct fb_info *info, int user);


/* For framebuffers with strange non linear layouts or that do not
* work with normal memory mapped access
*/
ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
  size_t count, loff_t *ppos);
ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
   size_t count, loff_t *ppos);

/* checks var and eventually tweaks it to something supported,
* DO NOT MODIFY PAR */
int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);

/* set the video mode according to info->var */
int (*fb_set_par)(struct fb_info *info);

/* set color register */
int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
   unsigned blue, unsigned transp, struct fb_info *info);


/* set color registers in batch */
int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);

/* blank display */
int (*fb_blank)(int blank, struct fb_info *info);

/* pan display */
int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);

/* Draws a rectangle */
void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
/* Copy data from area to another */
void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
/* Draws a image to the display */
void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);

/* Draws cursor */
int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);

/* Rotates the display */
void (*fb_rotate)(struct fb_info *info, int angle);

/* wait for blit idle, optional */
int (*fb_sync)(struct fb_info *info);

/* perform fb specific ioctl (optional) */
int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
unsigned long arg);

/* Handle 32bit compat ioctl (optional) */
int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
unsigned long arg);

/* perform fb specific mmap */
int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);

/* get capability given var */
void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
   struct fb_var_screeninfo *var);

/* teardown any resources to do with this framebuffer */
void (*fb_destroy)(struct fb_info *info);

/* called at KDB enter and leave time to prepare the console */
int (*fb_debug_enter)(struct fb_info *info);
int (*fb_debug_leave)(struct fb_info *info);
};

对于s3c6410的framebuffer驱动支持的操作主要有s3cfb_ops变量中定义，该变量类型为struct fb_ops，如上，该类型的定义在include/linux/fb.h文件中。它的相关解释可以http://www.91linux.com/html/article/kernel/20071204/8805.html页面中找到，当然在fb.h中也有很详细的说明。下面看看对于s3c6410的驱动为该framebuffer提供了哪些操作。

struct fb_ops s3cfb_ops = {
.owner  = THIS_MODULE,
.fb_check_var  = s3cfb_check_var,
.fb_set_par  = s3cfb_set_par,
.fb_blank          = s3cfb_blank,
.fb_pan_display= s3cfb_pan_display,
.fb_setcolreg  = s3cfb_setcolreg,
.fb_fillrect          = cfb_fillrect,
.fb_copyarea  = cfb_copyarea,
.fb_imageblit  = cfb_imageblit,
.fb_cursor  = soft_cursor,
.fb_ioctl          = s3cfb_ioctl,
};

上面的代码描述了支持的相关操作，下面主要会解释s3c6410****的函数。这里还有一个问题要说明一下，就是s3cfb_ops是在什么时候被注册的，这个问题的答案可以在s3cfb_probe函数中找到，请查看s3cfb_probe分析的那一小节。

4.2.1 s3cfb_check_var
       在上面的小节中提到对于一个LCD屏来说内核提供了两组数据结构来描述它，一组是可变属（fb_var_screeninfo描述），另一组是不变属性（fb_fix_screeninfo描述）。对于可变属性，应该防止在操作的过程中出现超出法定范围的情况，因此内核应该可以调用相关函数来检测、并将这些属性固定在法定的范围内，完成这个操作的函数就是s3cfb_check_var。
下面简单说明一下该函数要做的事情，在这里最好看着fb_var_screeninfo和fb_info的定义。
/*
 * s3cfb_check_var():
 * Get the video params out of 'var'. If a value doesn't fit, round it up,
 * if it's too big, return -EINVAL.
 *
 */
static int s3cfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
s3cfb_info_t *fbi = (s3cfb_info_t *) info;


DPRINTK("check_var(var=%p, info=%p)\n", var, info);

switch (var->bits_per_pixel) {
case 8:
var->red = s3cfb_rgb_8.red;
var->green = s3cfb_rgb_8.green;
var->blue = s3cfb_rgb_8.blue;
var->transp = s3cfb_rgb_8.transp;
s3cfb_fimd.bytes_per_pixel = 1;
break;

case 16:
var->red = s3cfb_rgb_16.red;
var->green = s3cfb_rgb_16.green;
var->blue = s3cfb_rgb_16.blue;
var->transp = s3cfb_rgb_16.transp;
s3cfb_fimd.bytes_per_pixel = 2;
break;

case 24:
var->red = s3cfb_rgb_24.red;
var->green = s3cfb_rgb_24.green;
var->blue = s3cfb_rgb_24.blue;
var->transp = s3cfb_rgb_24.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;

case 28:
var->red = s3cfb_rgb_28.red;
var->green = s3cfb_rgb_28.green;
var->blue = s3cfb_rgb_28.blue;
var->transp = s3cfb_rgb_28.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;

case 32:
var->red = s3cfb_rgb_32.red;
var->green = s3cfb_rgb_32.green;
var->blue = s3cfb_rgb_32.blue;
var->transp = s3cfb_rgb_32.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;
}

/* WIN0 cannot support alpha channel. */
if( (fbi->win_id == 0) && (var->bits_per_pixel == 28) ){
var->transp.length = 0;
}

return 0;
}

4.2.2 s3cfb_set_par
        该函数的主要工作是重新设置驱动的私有数据信息，主要改变的属性有bpp和行的长度（以字节为单位）。这些属性值其实是存放在fb_fix_screeninfo结构中的，前面说过这些值在运行基本是不会改变的，这些不可改变的值又可分为绝对不能改变和允许改变的两种类型，前一种的例子就是帧缓冲区的起始地址，后一种的例子就是在s3cfb_set_par函数中提到的属性。假如应用程序需要修改硬件的显示状态之类的操作，这个函数就显得十分重要。
/*
 *      s3cfb_set_par - Optional function. Alters the hardware state.
 *      @info: frame buffer structure that represents a single frame buffer
 *
 */
static int s3cfb_set_par(struct fb_info *info)
{
struct fb_var_screeninfo *var = &info->var;//可变的数据属性
s3cfb_info_t *fbi = (s3cfb_info_t *) info;


        if (var->bits_per_pixel == 16 || var->bits_per_pixel == 24 || var->bits_per_pixel == 28)
fbi->fb.fix.visual = FB_VISUAL_TRUECOLOR;真彩色
else
fbi->fb.fix.visual = FB_VISUAL_PSEUDOCOLOR;伪彩色

fbi->fb.fix.line_length = var->width * s3cfb_fimd.bytes_per_pixel;
修改行长度信息（以字节为单位），计算方法是一行中的(像素总数 * 表达每个像素的位数)/8。
/* activate this new configuration */
s3cfb_activate_var(fbi, var);该函数实际是设置硬件寄存器，解释略
return 0;
}

4.2.3 s3cfb_blank和s3cfb_setcolreg

       对于s3cfb_blank函数实现的功能非常简单，而且也有较详细的说明，因此对它的说明就省略了。s3cfb_setcolreg函数的功能是设置颜色寄存器。它需要6个参数，分别代表寄存器编号，红色，绿色，蓝色，透明和fb_info结构。

/**
 *      s3cfb_blank
 * @blank_mode: the blank mode we want.
 * @info: frame buffer structure that represents a single frame buffer
 *
 * Blank the screen if blank_mode != 0, else unblank. Return 0 if
 * blanking succeeded, != 0 if un-/blanking failed due to e.g. a
 * video mode which doesn't support it. Implements VESA suspend
 * and powerdown modes on hardware that supports disabling hsync/vsync:
 * blank_mode == 2: suspend vsync
 * blank_mode == 3: suspend hsync
 * blank_mode == 4: powerdown
 *
 * Returns negative errno on error, or zero on success.
 *
 */
static int s3cfb_blank(int blank_mode, struct fb_info *info)
{
DPRINTK("blank(mode=%d, info=%p)\n", blank_mode, info);

switch (blank_mode) {
case VESA_NO_BLANKING:/* lcd on, backlight on */
s3cfb_set_lcd_power(1);
s3cfb_set_backlight_power(1);
break;

case VESA_VSYNC_SUSPEND: /* lcd on, backlight off */
case VESA_HSYNC_SUSPEND:
s3cfb_set_lcd_power(1);
s3cfb_set_backlight_power(0);
break;

case VESA_POWERDOWN: /* lcd and backlight off */
s3cfb_set_lcd_power(0);
s3cfb_set_backlight_power(0);
break;

default:
return -EINVAL;
}

return 0;
}

static int s3cfb_setcolreg(unsigned int regno, unsigned int red, unsigned int green, unsigned int blue, unsigned int transp, struct fb_info *info)
{
s3cfb_info_t *fbi = (s3cfb_info_t *)info;
unsigned int val = 0;


switch (fbi->fb.fix.visual) {
case FB_VISUAL_TRUECOLOR:真彩色，使用了调色板
if (regno < 16) {
/* Fake palette of 16 colors */ 
unsigned int *pal = fbi->fb.pseudo_palette;

根据颜色值生成需要的数据
val = s3cfb_chan_to_field(red, fbi->fb.var.red);
val |= s3cfb_chan_to_field(green, fbi->fb.var.green);
val |= s3cfb_chan_to_field(blue, fbi->fb.var.blue);
val |= s3cfb_chan_to_field(transp, fbi->fb.var.transp);


pal[regno] = val;
}


break;


case FB_VISUAL_PSEUDOCOLOR:/* This means that the color format isn't 16, 24, 28 bpp. */
/* S3C6410 has 256 palette entries */
if (regno < 256) {
/* When var.bits_per_pixel is 8bp, then WIN0's palette is always set as 16 bit */
val = ((red >> 0) & 0xf800);
val |= ((green >> 5) & 0x07e0);
val |= ((blue >> 11) & 0x001f);


DPRINTK("index = %d, val = 0x%08x\n", regno, val);
s3cfb_update_palette(fbi, regno, val);更新相关寄存器
}

break;

default:
return 1; /* unknown type */
}
return 0;
}

下面来看看对编写应用层程序非常重要的一个函数s3cfb_ioctl，应用程序都是利用ioctl设置Frambuffer的。

int s3cfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
{
s3cfb_info_t *fbi = container_of(info, s3cfb_info_t, fb);
s3cfb_win_info_t win_info;
s3cfb_color_key_info_t colkey_info;
s3cfb_color_val_info_t colval_info;
s3cfb_dma_info_t dma_info;
s3cfb_next_info_t next_fb_info;
struct fb_var_screeninfo *var= &fbi->fb.var;
unsigned int crt, alpha_level, alpha_mode;


#if defined(CONFIG_S3C6410_PWM)
int brightness;
#endif


#if defined(CONFIG_FB_S3C_EXT_DOUBLE_BUFFERING)
unsigned int f_num_val;
#endif


#if defined(CONFIG_FB_S3C_EXT_VIRTUAL_SCREEN)
s3cfb_vs_info_t vs_info;
#endif

switch(cmd){
case S3CFB_GET_INFO:
dma_info.map_dma_f1 = fbi->map_dma_f1;
dma_info.map_dma_f2 = fbi->map_dma_f2;

if(copy_to_user((void *) arg, (const void *) &dma_info, sizeof(s3cfb_dma_info_t)))
return -EFAULT;
break;

case S3CFB_OSD_SET_INFO:
if (copy_from_user(&win_info, (s3cfb_win_info_t *) arg, sizeof(s3cfb_win_info_t)))
return -EFAULT;

s3cfb_init_win(fbi, win_info.bpp, win_info.left_x, win_info.top_y, win_info.width, win_info.height, OFF);
break;

case S3CFB_OSD_START:
s3cfb_onoff_win(fbi, ON);
break;

case S3CFB_OSD_STOP:
s3cfb_onoff_win(fbi, OFF);
break;

case S3CFB_OSD_ALPHA_UP:
alpha_level = readl(S3C_VIDOSD0C + (0x10 * fbi->win_id)) & 0xf;


if (alpha_level < S3CFB_MAX_ALPHA_LEVEL)
alpha_level++;

s3cfb_set_alpha_level(fbi, alpha_level, 1);
break;

case S3CFB_OSD_ALPHA_DOWN:
alpha_level = readl(S3C_VIDOSD0C + (0x10 * fbi->win_id)) & 0xf;

if (alpha_level > 0)
alpha_level--;

s3cfb_set_alpha_level(fbi, alpha_level, 1);
break;

case S3CFB_OSD_ALPHA0_SET:
alpha_level = (unsigned int) arg;


if (alpha_level > S3CFB_MAX_ALPHA_LEVEL)
alpha_level = S3CFB_MAX_ALPHA_LEVEL;

s3cfb_set_alpha_level(fbi, alpha_level, 0);
break;

case S3CFB_OSD_ALPHA1_SET:
alpha_level = (unsigned int) arg;

if (alpha_level > S3CFB_MAX_ALPHA_LEVEL)
alpha_level = S3CFB_MAX_ALPHA_LEVEL;

s3cfb_set_alpha_level(fbi, alpha_level, 1);
break;

case S3CFB_OSD_ALPHA_MODE:
alpha_mode = (unsigned int) arg;
s3cfb_set_alpha_mode(fbi, alpha_mode);
break;

case S3CFB_OSD_MOVE_LEFT:
if (var->xoffset > 0)
var->xoffset--;


s3cfb_set_win_position(fbi, var->xoffset, var->yoffset, var->xres, var->yres);
break;

case S3CFB_OSD_MOVE_RIGHT:
if (var->xoffset < (s3cfb_fimd.width - var->xres))
var->xoffset++;

s3cfb_set_win_position(fbi, var->xoffset, var->yoffset, var->xres, var->yres);
break;

case S3CFB_OSD_MOVE_UP:
if (var->yoffset > 0)
var->yoffset--;

s3cfb_set_win_position(fbi, var->xoffset, var->yoffset, var->xres, var->yres);
break;

case S3CFB_OSD_MOVE_DOWN:
if (var->yoffset < (s3cfb_fimd.height - var->yres))
var->yoffset++;

s3cfb_set_win_position(fbi, var->xoffset, var->yoffset, var->xres, var->yres);
break;

case FBIO_WAITFORVSYNC:
if (get_user(crt, (unsigned int __user *)arg))
return -EFAULT;

return s3cfb_wait_for_vsync();

case S3CFB_COLOR_KEY_START:
s3cfb_onoff_color_key(fbi, ON);
break;

case S3CFB_COLOR_KEY_STOP:
s3cfb_onoff_color_key(fbi, OFF);
break;

case S3CFB_COLOR_KEY_ALPHA_START:
s3cfb_onoff_color_key_alpha(fbi, ON);
break;

case S3CFB_COLOR_KEY_ALPHA_STOP:
s3cfb_onoff_color_key_alpha(fbi, OFF);
break;

case S3CFB_COLOR_KEY_SET_INFO:
if (copy_from_user(&colkey_info, (s3cfb_color_key_info_t *) arg, sizeof(s3cfb_color_key_info_t)))
return -EFAULT;

s3cfb_set_color_key_registers(fbi, colkey_info);
break;

case S3CFB_COLOR_KEY_VALUE:
if (copy_from_user(&colval_info, (s3cfb_color_val_info_t *) arg, sizeof(s3cfb_color_val_info_t)))
return -EFAULT;

s3cfb_set_color_value(fbi, colval_info);
break;

case S3CFB_SET_VSYNC_INT:
s3cfb_fimd.vidintcon0 &= ~S3C_VIDINTCON0_FRAMESEL0_MASK;
s3cfb_fimd.vidintcon0 |= S3C_VIDINTCON0_FRAMESEL0_VSYNC;

if (arg)
s3cfb_fimd.vidintcon0 |= S3C_VIDINTCON0_INTFRMEN_ENABLE;
else
s3cfb_fimd.vidintcon0 &= ~S3C_VIDINTCON0_INTFRMEN_ENABLE;


writel(s3cfb_fimd.vidintcon0, S3C_VIDINTCON0);
break;

case S3CFB_SET_NEXT_FB_INFO:
if (copy_from_user(&next_fb_info, (s3cfb_next_info_t *) arg, sizeof(s3cfb_next_info_t)))
return -EFAULT;


/* check arguments */
if ((next_fb_info.xres + next_fb_info.xoffset) > next_fb_info.xres_virtual ||
(next_fb_info.yres + next_fb_info.yoffset) > next_fb_info.yres_virtual ||
(next_fb_info.xres + next_fb_info.lcd_offset_x ) > s3cfb_fimd.width ||
(next_fb_info.yres + next_fb_info.lcd_offset_y ) > s3cfb_fimd.height) {
printk("Error : S3CFB_SET_NEXT_FB_INFO\n");
  return -EINVAL;
}

fbi->next_fb_info = next_fb_info;
fbi->next_fb_info_change_req = 1;
break;

case S3CFB_GET_CURR_FB_INFO:
next_fb_info.phy_start_addr = fbi->fb.fix.smem_start;
next_fb_info.xres = fbi->fb.var.xres;
next_fb_info.yres = fbi->fb.var.yres;
next_fb_info.xres_virtual = fbi->fb.var.xres_virtual;
next_fb_info.yres_virtual = fbi->fb.var.yres_virtual;
next_fb_info.xoffset = fbi->fb.var.xoffset;
next_fb_info.yoffset = fbi->fb.var.yoffset;
next_fb_info.lcd_offset_x = fbi->lcd_offset_x;
next_fb_info.lcd_offset_y = fbi->lcd_offset_y;


if (copy_to_user((void *)arg, (s3cfb_next_info_t *) &next_fb_info, sizeof(s3cfb_next_info_t)))
return -EFAULT;
break;


case S3CFB_GET_BRIGHTNESS:
if (copy_to_user((void *)arg, (const void *) &s3cfb_fimd.brightness, sizeof(int)))
return -EFAULT;
break;


#if defined(CONFIG_S3C6410_PWM)
case S3CFB_SET_BRIGHTNESS:
if (copy_from_user(&brightness, (int *) arg, sizeof(int)))
return -EFAULT;


s3cfb_set_brightness(brightness);
break;
#endif


#if defined(CONFIG_FB_S3C_EXT_VIRTUAL_SCREEN)
case S3CFB_VS_START:
s3cfb_fimd.wincon0 &= ~(S3C_WINCONx_ENWIN_F_ENABLE);
writel(s3cfb_fimd.wincon0 | S3C_WINCONx_ENWIN_F_ENABLE, S3C_WINCON0);


fbi->fb.var.xoffset = s3cfb_fimd.xoffset;
fbi->fb.var.yoffset = s3cfb_fimd.yoffset;
break;


case S3CFB_VS_STOP:
s3cfb_fimd.vidw00add0b0 = fbi->screen_dma_f1;
s3cfb_fimd.vidw00add0b1 = fbi->screen_dma_f2;
fbi->fb.var.xoffset = 0;
fbi->fb.var.yoffset = 0;


writel(s3cfb_fimd.vidw00add0b0, S3C_VIDW00ADD0B0);
writel(s3cfb_fimd.vidw00add0b1, S3C_VIDW00ADD0B1);


break;


case S3CFB_VS_SET_INFO:
if (copy_from_user(&vs_info, (s3cfb_vs_info_t *) arg, sizeof(s3cfb_vs_info_t)))
return -EFAULT;


if (s3cfb_set_vs_info(vs_info)) {
printk("Error S3CFB_VS_SET_INFO\n");
return -EINVAL;
}


s3cfb_set_vs_registers(S3CFB_VS_SET);


fbi->fb.var.xoffset = s3cfb_fimd.xoffset;
fbi->fb.var.yoffset = s3cfb_fimd.yoffset;
break;


case S3CFB_VS_MOVE:
s3cfb_set_vs_registers(arg);


fbi->fb.var.xoffset = s3cfb_fimd.xoffset;
fbi->fb.var.yoffset = s3cfb_fimd.yoffset;
break;
#endif


#if defined(CONFIG_FB_S3C_EXT_DOUBLE_BUFFERING)
case S3CFB_GET_NUM:
if (copy_from_user((void *)&f_num_val, (const void *)arg, sizeof(u_int)))
return -EFAULT;


if (copy_to_user((void *)arg, (const void *) &f_num_val, sizeof(u_int)))
return -EFAULT;

break;

case S3CFB_CHANGE_REQ:
s3cfb_change_buff(0, (int) arg);
break;
#endif

default:
return -EINVAL;
}
return 0;
}

到目前为止，整个驱动的主要部分已经解释完毕了。最后还是得提一下中断处理函数s3cfb_irq，这个函数实现也比较短，它的主要调用了s3c2410fb_write_palette函数将它的功能是将调色板中的数据显示到LCD上。两个函数的实现也不难，这里就不再赘述。
OK！good bye everyone！see you next time。
The End