Android System Programming

Allocating from system memory

When the usage bit is not set to GRALLOC_USAGE_HW_FB or the system cannot support double buffering, we have to allocate the buffer from system memory using gralloc_alloc_buffer. Let's look at the implementation of gralloc_alloc_buffer:

static int gralloc_alloc_buffer(alloc_device_t* dev,         size_t size, int /*usage*/, buffer_handle_t* pHandle) {     int err = 0;     int fd = -1;     size = roundUpToPageSize(size);     fd = ashmem_create_region("gralloc-buffer", size);     if (fd < 0) {         ALOGE("couldn't create ashmem (%s)", strerror(-errno));         err = -errno;     }     if (err == 0) {         private_handle_t* hnd = new private_handle_t(fd, size, 0);         gralloc_module_t* module = reinterpret_cast<gralloc_module_t*>(                 dev->common.module);  err ...