From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:45653 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759414Ab2JKVsv (ORCPT ); Thu, 11 Oct 2012 17:48:51 -0400 From: Laurent Pinchart To: Tomasz Stanislawski Cc: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@redhat.com, m.szyprowski@samsung.com, kyungmin.park@samsung.com, sumit.semwal@ti.com, daeinki@gmail.com, daniel.vetter@ffwll.ch, robdclark@gmail.com, pawel@osciak.com, linaro-mm-sig@lists.linaro.org, hverkuil@xs4all.nl, remi@remlab.net, subashrp@gmail.com, mchehab@redhat.com, zhangfei.gao@gmail.com, s.nawrocki@samsung.com, k.debski@samsung.com Subject: Re: [PATCHv10 21/26] v4l: vb2-dma-contig: add reference counting for a device from allocator context Date: Thu, 11 Oct 2012 23:49:36 +0200 Message-ID: <1557711.XL0Wq5VHNW@avalon> In-Reply-To: <1349880405-26049-22-git-send-email-t.stanislaws@samsung.com> References: <1349880405-26049-1-git-send-email-t.stanislaws@samsung.com> <1349880405-26049-22-git-send-email-t.stanislaws@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Tomasz, Thanks for the patch. On Wednesday 10 October 2012 16:46:40 Tomasz Stanislawski wrote: > This patch adds taking reference to the device for MMAP buffers. > > Such buffers, may be exported using DMABUF mechanism. If the driver that > created a queue is unloaded then the queue is released, the device might be > released too. However, buffers cannot be released if they are referenced by > DMABUF descriptor(s). The device pointer kept in a buffer must be valid for > the whole buffer's lifetime. Therefore MMAP buffers should take a reference > to the device to avoid risk of dangling pointers. > > Signed-off-by: Tomasz Stanislawski > Acked-by: Hans Verkuil Acked-by: Laurent Pinchart But two small comments below. > --- > drivers/media/v4l2-core/videobuf2-dma-contig.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c > b/drivers/media/v4l2-core/videobuf2-dma-contig.c index b138b5c..2d661fd > 100644 > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c > @@ -148,6 +148,7 @@ static void vb2_dc_put(void *buf_priv) > kfree(buf->sgt_base); > } > dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr); > + put_device(buf->dev); > kfree(buf); > } > > @@ -168,6 +169,9 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long > size) return ERR_PTR(-ENOMEM); > } > > + /* prevent the device from release while the buffer is exported */ s/prevent/Prevent/ ? > + get_device(dev); > + > buf->dev = dev; What about just buf->dev = get_device(dev); > buf->size = size; -- Regards, Laurent Pinchart