Hi, I have a question about memory freeing by calling REQBUF(0) before all the dmabuf fds exported with VIDIOC_EXPBUF are closed. In calling REQBUF(0), videobuf2-core returns -EBUSY when the reference count of a vb2 buffer is more than 1. When dmabuf fds are not exported (usual V4L2_MEMORY_MMAP case), the check is no problem, but when dmabuf fds are exported and some of them are not closed (in other words the references to that memory are left), we cannot succeed in calling REQBUF(0) despite being able to free the memory after all the references are dropped. Actually REQBUF(0) does not force a vb2 buffer to be freed but decreases the refcount of it. Also all the vb2 memory allocators that support dmabuf exporting (dma-contig, dma-sg, vmalloc) implements memory freeing by release() of dma_buf_ops, so I think there is no need to return -EBUSY when exporting dmabuf fds. Could you please tell me what you think? The code that I am talking about is in drivers/media/v4l2-core/videobuf2-core.c: if (*count == 0 || q->num_buffers != 0 || q->memory != memory) { /* * We already have buffers allocated, so first check if they * are not in use and can be freed. */ mutex_lock(&q->mmap_lock); if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) { mutex_unlock(&q->mmap_lock); dprintk(1, "memory in use, cannot free\n"); return -EBUSY; } Regards, Kobayashi -- --------------------------------- IGEL Co.,Ltd. Kazunori Kobayashi kkobayas@xxxxxxxxxx http://www.igel.co.jp/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html