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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bqH5FBNU; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E1AE606A31A; Wed, 28 Oct 2026 12:32:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bqH5FBNU Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C3821F01828; Wed, 28 Oct 2026 12:32:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793190740; bh=v9I8aBwYQiXna0K4b9R5EzdMw2Iyv8e6dSEyABp9uOI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=bqH5FBNUwWBoVI2G2c+7UPWAdL6oXWKWhvaa4sWh2CFSm7sZKUiyjNb9H665iWUU4 ePEe5BBHybJYpWfOQF+bfkzuNp1/x2onspl99RhN64L6cAmIiW4gi0eTZ/j2blG/w0 U5C7m6RIDXm/uw981ZGOMqRe9m/dMPaMgO5oc7bhQ3Ty8uW9MHa+jlSpqcSRQ1W3X3 /27YzeNK1kPKZOUzJXICGQMCVJDnhMjXvMm5r7NhawV1EUAis0LfUbZWHfGw/o5BKu /7DCY019NQzFWsdYP0pJGcGATj0jiQJtq+GeKlI3XMXwfoTetzMMW1JqVMbMqNHX6/ qo1zPIo8jk2+A== Message-ID: <0f436944-fa9a-49f9-ac1d-8779a36ab13d@kernel.org> Date: Wed, 28 Oct 2026 12:32:15 +0000 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/9] media: camss: video: check that a buffer is DMA contiguous and add a prepare hook To: Qianhui Xu , 'Bryan O'Donoghue' , Mauro Carvalho Chehab Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Hangxiang Ma , linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261028093003.722745-1-xiaqinghuan@mail.ustc.edu.cn> <20261028093003.722745-7-xiaqinghuan@mail.ustc.edu.cn> From: Bryan O'Donoghue Content-Language: en-GB Autocrypt: addr=bod@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28/10/2026 09:30, Qianhui Xu wrote: > The write master of the newer VFE generations can only be programmed with > a buffer whose payload is physically contiguous, because the frame > increment registers describe one linear address range. Check that the DMA > mapping of every plane is contiguous for at least sizeimage bytes and > reject the buffer otherwise, instead of silently writing past the end of > the first scatterlist entry. > > Also let the SoC code add its own alignment requirements to a queued > buffer through a new prepare_buffer() video operation, which runs after > the generic checks. > > Signed-off-by: Qianhui Xu > --- > .../media/platform/qcom/camss/camss-video.c | 18 +++++++++++++++++- > .../media/platform/qcom/camss/camss-video.h | 1 + > 2 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/platform/qcom/camss/camss-video.c b/drivers/media/platform/qcom/camss/camss-video.c > index 0852eb6f1..027cf024f 100644 > --- a/drivers/media/platform/qcom/camss/camss-video.c > +++ b/drivers/media/platform/qcom/camss/camss-video.c > @@ -155,7 +155,10 @@ static int video_buf_init(struct vb2_buffer *vb) > const struct v4l2_pix_format_mplane *format = > &video->active_fmt.fmt.pix_mp; > struct sg_table *sgt; > - unsigned int i; > + struct scatterlist *sg; > + dma_addr_t end; > + unsigned int i, j; > + size_t contiguous; > > for (i = 0; i < format->num_planes; i++) { > sgt = vb2_dma_sg_plane_desc(vb, i); > @@ -163,6 +166,16 @@ static int video_buf_init(struct vb2_buffer *vb) > return -EFAULT; > > buffer->addr[i] = sg_dma_address(sgt->sgl); > + end = buffer->addr[i]; > + contiguous = 0; > + for_each_sgtable_dma_sg(sgt, sg, j) { > + if (sg_dma_address(sg) != end) > + break; > + contiguous += sg_dma_len(sg); > + end += sg_dma_len(sg); > + } > + if (contiguous < format->plane_fmt[i].sizeimage) > + return -EINVAL; > } Is it really the case we can only do physically contiguous on sm8750 ? Hrmm, first I've heard of this, it would be a gigantic step backwards too. Can you cite some sources to prove this out ? --- bod