android2.3.4----4.hal与framebuffer的交互

原文地址：http://blog.chinaunix.net/uid-26009923-id-4044926.html
一. 打开gralloc
在frameworks/base/libs/ui/FramebufferNativeWindow.cpp中会调用

FramebufferNativeWindow::FramebufferNativeWindow()
    : BASE(), fbDev(0), grDev(0), mUpdateOnDemand(false)
{
    hw_module_t const* module;
    hw_get_module(GRALLOC_HARDWARE_MODULE_ID, &module); //1.加载gralloc库
    framebuffer_open(module, &fbDev);                   //2.打开fb设备
    gralloc_open(module, &grDev);
}

其中在./hardware/libhardware/include/hardware/gralloc.h中定义了
#define GRALLOC_HARDWARE_MODULE_ID "gralloc"
1. 加载gralloc库,并初始化hw_module_t
在./hardware/libhardware/hardware.c中

int hw_get_module(const char *id, const struct hw_module_t **module)
{
    int status;
    int i;
    const struct hw_module_t *hmi = NULL;
    char prop[PATH_MAX];
    char path[PATH_MAX];
    //查找gralloc库在板子上实际的名字与路径,将真正的文件名的路径存于path中
    for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {
        if (i < HAL_VARIANT_KEYS_COUNT) {
            if (property_get(variant_keys[i], prop, NULL) == 0) {
                continue;
            }
            //在"/system/lib/hw"目录下查找 gralloc.>.so
            snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH1, id, prop);
            if (access(path, R_OK) == 0)
                break;
            //在"/vendor/lib/hw"目录下查找 gralloc.>.so
            snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH2, id, prop);
            if (access(path, R_OK) == 0)
                break;
        } else {
            //在板子上这两个都不存在,只好用默认的 /system/lib/hw/gralloc.default.so
            snprintf(path, sizeof(path), "%s/%s.default.so", HAL_LIBRARY_PATH1, id);
            if (access(path, R_OK) == 0)
                break;
        }
    }

    if (i < HAL_VARIANT_KEYS_COUNT+1) {
        status = load(id, path, module);  //加载/system/lib/hw/gralloc.default.so这个库
    }
}

1.1 加载/system/lib/hw/gralloc.default.so这个库
在./hardware/libhardware/modules/gralloc/gralloc.cpp中

static int load(const char *id, const char *path, const struct hw_module_t **pHmi)
{
    void *handle = dlopen(path, RTLD_NOW);  //dlopen会加载共享库
    const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
    struct hw_module_t *hmi = (struct hw_module_t *)dlsym(handle, sym);  //dlsym会定位到"HMI"处
    //注意android共享库的"HMI"处是一个private_module_t(gralloc.cpp中有定义)
    if (strcmp(id, hmi->id) != 0) {
        status = -EINVAL;
        goto done;
    }

    hmi->dso = handle;     //把
    *pHmi = hmi;
}

把上面的 struct hw_module_t *hmi = (struct hw_module_t *)dlsym(handle, sym);
改为 struct hw_module_t private_module_t *hmi = (struct private_module_t *)dlsym(handle, sym);
更好理解一点,与突然直接转为 hw_module_t时,效果一样.
下面是private_module_t结构体的分解,开头都是一个struct hw_module_t.
struct private_module_t
{
    gralloc_module_t base;  -->   struct hw_module_t common;  --> tag 
                                                                                                 -->  id = GRALLOC_HARDWARE_MODULE_ID
                                                                                                 -->  methods = gralloc_module_methods
                                         -->   加一些函数指针                          
}
2.1 fb设备的打开过程
framebuffer_open(module, &fbDev);

static inline int framebuffer_open(const struct hw_module_t* module, struct framebuffer_device_t** device) {
    return module->methods->open(module, GRALLOC_HARDWARE_FB0, (struct hw_device_t**)device);
}

在load中methods被初始化为
static struct hw_module_methods_t gralloc_module_methods = {
        open: gralloc_device_open
};
所以这儿的open就是要调用gralloc_device_open
2.2 gralloc_device_open
framebuffer_open
--> gralloc_device_open
在./hardware/libhardware/modules/gralloc/gralloc.cpp中

int gralloc_device_open(const hw_module_t* module, const char* name,   hw_device_t** device)
{
    int status = -EINVAL;
    if (!strcmp(name, GRALLOC_HARDWARE_GPU0)) {
    } else {    //name=="fb0"
        status = fb_device_open(module, name, device);  //2.2.1这儿只关注fb的打开过程
    }
    return status;
}

2.2.1 打开fb的具体过程
framebuffer_open
--> gralloc_device_open
    --> fb_device_open
在./hardware/libhardware/modules/gralloc/framebuffer.cpp中
这个函数主要是初始化一个fb_context_t结构体并调用mapFrameBuffer来初始化

int fb_device_open(hw_module_t const* module, const char* name, hw_device_t** device)
{
    int status = -EINVAL;
    if (!strcmp(name, GRALLOC_HARDWARE_FB0)) {
        alloc_device_t* gralloc_device;
        status = gralloc_open(module, &gralloc_device);
        fb_context_t *dev = (fb_context_t*)malloc(sizeof(*dev));
        memset(dev, 0, sizeof(*dev));

        dev->device.common.tag = HARDWARE_DEVICE_TAG;
        dev->device.common.version = 0;
        dev->device.common.module = const_cast<hw_module_t*>(module);
        dev->device.common.close = fb_close;
        dev->device.setSwapInterval = fb_setSwapInterval;
        dev->device.post = fb_post;
        dev->device.setUpdateRect = 0;

        private_module_t* m = (private_module_t*)module;
        status = mapFrameBuffer(m);            //2.2.1.1这个函数map
        if (status >= 0) {
            int stride = m->finfo.line_length / (m->info.bits_per_pixel >> 3);
            int format = HAL_PIXEL_FORMAT_RGB_565;
            const_cast<uint32_t&>(dev->device.flags) = 0;
            const_cast<uint32_t&>(dev->device.width) = m->info.xres;
            const_cast<uint32_t&>(dev->device.height) = m->info.yres;
            const_cast<int&>(dev->device.stride) = stride;
            const_cast<int&>(dev->device.format) = format;
            const_cast<float&>(dev->device.xdpi) = m->xdpi;
            const_cast<float&>(dev->device.ydpi) = m->ydpi;
            const_cast<float&>(dev->device.fps) = m->fps;
            const_cast<int&>(dev->device.minSwapInterval) = 1;
            const_cast<int&>(dev->device.maxSwapInterval) = 1;
            *device = &dev->device.common;
        }
    }
    return status;
}

2.2.1.1 mapFrameBuffer
framebuffer_open
--> gralloc_device_open
    --> fb_device_open
        --> mapFrameBuffer

static int mapFrameBuffer(struct private_module_t* module)
{
    pthread_mutex_lock(&module->lock);
    int err = mapFrameBufferLocked(module);
    pthread_mutex_unlock(&module->lock);
    return err;
}

2.2.1.2 mapFrameBufferLocked

---

framebuffer_open
--> gralloc_device_open
    --> fb_device_open
        --> mapFrameBuffer
        --> mapFrameBufferLocked
 mapFrameBuffer./hardware/libhardware/modules/gralloc/framebuffer.cpp中

int mapFrameBufferLocked(struct private_module_t* module)
{
    char const * const device_template[] = {
        "/dev/graphics/fb%u",
        "/dev/fb%u",
        0 };

    int fd = -1;
    int i=0;
    char name[64];
    //打开设备文件,先找/dev/graphics/fb*,找不到再找/dev/fb*
    while ((fd==-1) && device_template[i]) {
        snprintf(name, 64, device_template[i], 0);
        fd = open(name, O_RDWR, 0);
        i++;
    }
    if (fd < 0)
        return -errno;
    //1. 获取参数
    struct fb_fix_screeninfo finfo;
    ioctl(fd, FBIOGET_FSCREENINFO, &finfo);
    //2. 获取参数
    struct fb_var_screeninfo info;
    ioctl(fd, FBIOGET_VSCREENINFO, &info);
    //3.中间省略修改值,将修改之后的info写到内核空间
    ioctl(fd, FBIOPUT_VSCREENINFO, &info);

    if (info.yres_virtual < info.yres * 2) {
        info.yres_virtual = info.yres;
        flags &= ~PAGE_FLIP;
    }
    //3. 获取参数
    ioctl(fd, FBIOGET_VSCREENINFO, &info);

    uint64_t refreshQuotient =
        (
         uint64_t( info.upper_margin + info.lower_margin + info.yres )
         * ( info.left_margin + info.right_margin + info.xres )
         * info.pixclock
        );

    int refreshRate = refreshQuotient > 0 ? (int)(1000000000000000LLU / refreshQuotient) : 0;

    if (refreshRate == 0)
        refreshRate = 60*1000; // 60 Hz


    if (int(info.width) <= 0 || int(info.height) <= 0) {
        info.width = ((info.xres * 25.4f)/160.0f + 0.5f);
        info.height = ((info.yres * 25.4f)/160.0f + 0.5f);
    }

    float xdpi = (info.xres * 25.4f) / info.width;
    float ydpi = (info.yres * 25.4f) / info.height;
    float fps = refreshRate / 1000.0f;
    if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) == -1)
        return -errno;

    if (finfo.smem_len <= 0)
        return -errno;


    module->flags = flags;
    module->info = info;
    module->finfo = finfo;
    module->xdpi = xdpi;
    module->ydpi = ydpi;
    module->fps = fps;

    size_t fbSize = roundUpToPageSize(finfo.line_length * info.yres_virtual);
    module->framebuffer = new private_handle_t(dup(fd), fbSize, 0);

    module->numBuffers = info.yres_virtual / info.yres;
    module->bufferMask = 0;
    //mmap 一切准备都是为了这个函数
    void* vaddr = mmap(0, fbSize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    module->framebuffer->base = intptr_t(vaddr);   //保存这个值
    memset(vaddr, 0, fbSize);  //清屏
    return 0;
}

---

二. 显示过程:双缓冲的实现
1. 上层应用在调用fb_post进行显示
在./hardware/libhardware/modules/gralloc/framebuffer.cpp中

static int fb_post(struct framebuffer_device_t* dev, buffer_handle_t buffer)
{
    if (private_handle_t::validate(buffer) < 0)
        return -EINVAL;

    fb_context_t* ctx = (fb_context_t*)dev;

    private_handle_t const* hnd = reinterpret_cast<private_handle_t const*>(buffer);
    private_module_t* m = reinterpret_cast<private_module_t*>( dev->common.module);
    //直接映射显存空间到用户空间,这儿的PRIV_FLAGS_FRAMEBUFFER一直是置位状态
    if (hnd->flags & private_handle_t::PRIV_FLAGS_FRAMEBUFFER)
    {
        const size_t offset = hnd->base - m->framebuffer->base;
        m->info.activate = FB_ACTIVATE_VBL;
        m->info.yoffset = offset / m->finfo.line_length;
        ioctl(m->framebuffer->fd, FBIOPAN_DISPLAY,&m->info);     //2.1双缓冲
        unsigned int crtc = 0;
        ioctl(m->framebuffer->fd, FBIO_WAITFORVSYNC, &m->info);  //2.2等侍刷新结束
        m->currentBuffer = buffer;
    } else {              //没有执行
        void* fb_vaddr;
        void* buffer_vaddr;
        m->base.lock(&m->base, m->framebuffer, GRALLOC_USAGE_SW_WRITE_RARELY, 0, 0, m->info.xres, m->info.yres, &fb_vaddr);
        m->base.lock(&m->base, buffer, GRALLOC_USAGE_SW_READ_RARELY, 0, 0, m->info.xres, m->info.yres, &buffer_vaddr);
        memcpy(fb_vaddr, buffer_vaddr, m->finfo.line_length * m->info.yres);
        m->base.unlock(&m->base, buffer);
        m->base.unlock(&m->base, m->framebuffer);
    }
}

2. 调用驱动层
应用层fb_post  ---->ioctl(m->framebuffer->fd, FBIOPAN_DISPLAY,&m->info);
驱动层--> fb_ioctl
在驱动drivers/video/fbmem.c中

static long fb_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    int fbidx = iminor(inode);   //将/dev/fb0 或 /dev/fb1后面的数字解析出来,这儿是/dev/fb0
    struct fb_info *info = registered_fb[fbidx];  //通过/dev/fb0的index获取数组指针
    return do_fb_ioctl(info, cmd, arg);
}

应用层fb_post  ---->ioctl(m->framebuffer->fd, FBIOPAN_DISPLAY,&m->info);
驱动层--> fb_ioctl
            --> do_fb_ioctl
在驱动drivers/video/fbmem.c中

static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
{
    struct fb_ops *fb;
    struct fb_var_screeninfo var;
    struct fb_fix_screeninfo fix;
    struct fb_con2fbmap con2fb;
    struct fb_cmap cmap_from;
    struct fb_cmap_user cmap;
    struct fb_event event;
    void __user *argp = (void __user *)arg;
    long ret = 0;

    switch (cmd) {
    case FBIOPAN_DISPLAY:
        if (copy_from_user(&var, argp, sizeof(var)))
            return -EFAULT;
        if (!lock_fb_info(info))
            return -ENODEV;
        acquire_console_sem();
        ret = fb_pan_display(info, &var);      //2.1交错刷新frame1与frame2
        release_console_sem();
        unlock_fb_info(info);
        if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
            return -EFAULT;
        break;
    default:
        if (!lock_fb_info(info))
            return -ENODEV;
        fb = info->fbops;
        if (fb->fb_ioctl)
            ret = fb->fb_ioctl(info, cmd, arg);   //2.2等侍刷新结束
        else
            ret = -ENOTTY;
        unlock_fb_info(info);
    }
    return ret;
}

2.1 双缓冲的实现
通过设定framebuffer的起始与结束地址,来控制LCD的显示,
交错指定buffer0的起始地址为(0, screensize) 与(screensize, screensize*2)来进行frame1与frame2的切换
应用层fb_post  ---->ioctl(m->framebuffer->fd, FBIOPAN_DISPLAY,&m->info);
驱动层--> fb_ioctl
            --> do_fb_ioctl
                --> s3cfb_pan_display
在驱动drivers/video/samsun/s3cfb.c中

static int s3cfb_pan_display(struct fb_var_screeninfo *var, struct fb_info *info)
{
    s3cfb_info_t *fbi = (s3cfb_info_t *)info;

    fbi->fb.var.xoffset = var->xoffset;   //xoffset永远是0
    fbi->fb.var.yoffset = var->yoffset;   //yoffset 0与272间隔出现,即代表了frame1与frame2

    s3cfb_set_fb_addr(fbi);               //设置刷屏的起始地址

    return 0;
}

2.1.1控制frame1与frame2的切换
应用层fb_post   ---->ioctl(m->framebuffer->fd, FBIOPAN_DISPLAY,&m->info);
驱动层--> fb_ioctl
            --> do_fb_ioctl
                --> s3cfb_pan_display
                    --> s3cfb_set_fb_addr
在drivers/video/samsung/s3cfb_fimd4x.c中

void s3cfb_set_fb_addr(s3cfb_info_t *fbi)
{
    unsigned long video_phy_temp_f1 = fbi->screen_dma_f1;   //获取dma的物理地址
    //这儿的yoffset是0时就是frame1,yoffset=272时就是frame2
    unsigned int start = fbi->fb.fix.line_length * fbi->fb.var.yoffset;
    unsigned long start_address = video_phy_temp_f1 + start;  //将frame1或frame2的起始地址赋值
    unsigned long end_address = start_address + (fbi->fb.fix.line_length * fbi->fb.var.yres);
    switch (fbi->win_id)
    {
        case 0:
            s3cfb_fimd.vidw00add0b0 = start_address;
            s3cfb_fimd.vidw00add1b0 = end_address;
            //Window 0’s buffer start address register, buffer 0
            __raw_writel(s3cfb_fimd.vidw00add0b0, S3C_VIDW00ADD0B0);
            //Window 0’s buffer end address register, buffer 0
            __raw_writel(s3cfb_fimd.vidw00add1b0, S3C_VIDW00ADD1B0);
            break;
    }
}

2.2 等侍vsync结束
应用层fb_post  ---->ioctl(m->framebuffer->fd, FBIO_WAITFORVSYNC, &m->info);
驱动层--> fb_ioctl
            --> do_fb_ioctl  --> fb->fb_ioctl(info, cmd, arg);   //2.2等侍刷新结束
                --> s3cfb_ioctl
在drivers/video/samsung/s3cfb_fimd4x.c中

int s3cfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
{
    switch(cmd){
        case FBIO_WAITFORVSYNC:
            if (get_user(crt, (unsigned int __user *)arg))
                return -EFAULT;
            return s3cfb_wait_for_vsync();
    }
}

2.2.1 在下一次中断完成后返回
应用层fb_post  ---->ioctl(m->framebuffer->fd, FBIO_WAITFORVSYNC, &m->info);
驱动层--> fb_ioctl
            --> do_fb_ioctl  --> fb->fb_ioctl(info, cmd, arg);   //2.2等侍刷新结束
                --> s3cfb_ioctl
                    --> s3cfb_wait_for_vsync
在驱动drivers/video/samsun/s3cfb.c中

int s3cfb_wait_for_vsync(void)
{
    int cnt;
    cnt = s3cfb_fimd.vsync_info.count;  //获取cnt值,在下一次中断完成后才能返回.
    //wait_event_interruptible_timeout (wq, condition, timeout);
    //condition代表着下一次中断完成
    wait_event_interruptible_timeout(s3cfb_fimd.vsync_info.wait_queue, cnt != s3cfb_fimd.vsync_info.count, HZ / 10);
    return cnt;
}

2.2.2 中断处理函数
framebuffer的中断处理函数
只做两件事就是清中断与唤配等侍队列
在drivers/video/samsung/s3cfb_fimd4x.c中

irqreturn_t s3cfb_irq(int irqno, void *param)
{
    writel(readl(S3C_VIDINTCON1), S3C_VIDINTCON1);  //清中断

    s3cfb_fimd.vsync_info.count++;                  //唤醒等侍队列
    wake_up_interruptible(&s3cfb_fimd.vsync_info.wait_queue);

    return IRQ_HANDLED;
}

附录:
1. s3c_irq这个中断是何时被触发
a. 查看发生频率

/ # date && cat /proc/interrupts
Fri Jan 2 00:08:51 GMT 1970
 62: 35409 VIC s3c-lcd


/ # date && cat /proc/interrupts
Fri Jan 2 00:10:58 GMT 1970
 62: 43472 VIC s3c-lcd

(43472-35409)/127=63.488188976

说明这个中断大约每秒触发60次,即屏幕的刷新频率