Android System Programming

Allocating from framebuffer

As we can see from the gralloc_alloc function, when the usage bit is set to GRALLOC_USAGE_HW_FB, the gralloc_alloc_framebuffer function is called. The gralloc_alloc_framebuffer function will allocate the buffer from the framebuffer device:

static int gralloc_alloc_framebuffer_locked(alloc_device_t* dev,         size_t size, int usage, buffer_handle_t* pHandle) {     private_module_t* m = reinterpret_cast<private_module_t*>(             dev->common.module);     // allocate the framebuffer     if (m->framebuffer == NULL) {         // initialize the framebuffer, the framebuffer is mapped once         // and forever.         int err = mapFrameBufferLocked(m);         if (err < 0) {             return err;         }     }     const uint32_t bufferMask = m->bufferMask;  const uint32_t numBuffers ...