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From: "Ruhl, Michael J" <michael.j.ruhl@intel.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"linaro-mm-sig@lists.linaro.org" <linaro-mm-sig@lists.linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Pawel Osciak <pawel@osciak.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	David Airlie <airlied@linux.ie>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: RE: [PATCH v4 38/38] videobuf2: use sgtable-based scatterlist wrappers
Date: Wed, 13 May 2020 12:01:37 +0000
Message-ID: <14063C7AD467DE4B82DEDB5C278E8663010E211B19@FMSMSX108.amr.corp.intel.com> (raw)
In-Reply-To: <f6242137-82a5-0e33-f1a2-9e73dc679aa9@samsung.com>

>-----Original Message-----
>From: Marek Szyprowski <m.szyprowski@samsung.com>
>Sent: Tuesday, May 12, 2020 4:34 PM
>To: Ruhl, Michael J <michael.j.ruhl@intel.com>; dri-
>devel@lists.freedesktop.org; iommu@lists.linux-foundation.org; linaro-mm-
>sig@lists.linaro.org; linux-kernel@vger.kernel.org
>Cc: Pawel Osciak <pawel@osciak.com>; Bartlomiej Zolnierkiewicz
><b.zolnierkie@samsung.com>; David Airlie <airlied@linux.ie>; linux-
>media@vger.kernel.org; Hans Verkuil <hverkuil-cisco@xs4all.nl>; Mauro
>Carvalho Chehab <mchehab@kernel.org>; Robin Murphy
><robin.murphy@arm.com>; Christoph Hellwig <hch@lst.de>; linux-arm-
>kernel@lists.infradead.org
>Subject: Re: [PATCH v4 38/38] videobuf2: use sgtable-based scatterlist
>wrappers
>
>Hi Michael,
>
>On 12.05.2020 19:52, Ruhl, Michael J wrote:
>>> -----Original Message-----
>>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>> Marek Szyprowski
>>> Sent: Tuesday, May 12, 2020 5:01 AM
>>> To: dri-devel@lists.freedesktop.org; iommu@lists.linux-foundation.org;
>>> linaro-mm-sig@lists.linaro.org; linux-kernel@vger.kernel.org
>>> Cc: Pawel Osciak <pawel@osciak.com>; Bartlomiej Zolnierkiewicz
>>> <b.zolnierkie@samsung.com>; David Airlie <airlied@linux.ie>; linux-
>>> media@vger.kernel.org; Hans Verkuil <hverkuil-cisco@xs4all.nl>; Mauro
>>> Carvalho Chehab <mchehab@kernel.org>; Robin Murphy
>>> <robin.murphy@arm.com>; Christoph Hellwig <hch@lst.de>; linux-arm-
>>> kernel@lists.infradead.org; Marek Szyprowski
>>> <m.szyprowski@samsung.com>
>>> Subject: [PATCH v4 38/38] videobuf2: use sgtable-based scatterlist
>wrappers
>>>
>>> Use recently introduced common wrappers operating directly on the struct
>>> sg_table objects and scatterlist page iterators to make the code a bit
>>> more compact, robust, easier to follow and copy/paste safe.
>>>
>>> No functional change, because the code already properly did all the
>>> scaterlist related calls.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>> For more information, see '[PATCH v4 00/38] DRM: fix struct sg_table nents
>>> vs. orig_nents misuse' thread:
>>> https://lore.kernel.org/dri-devel/20200512085710.14688-1-
>>> m.szyprowski@samsung.com/T/
>>> ---
>>> .../media/common/videobuf2/videobuf2-dma-contig.c  | 41 ++++++++++-
>---
>>> --------
>>> drivers/media/common/videobuf2/videobuf2-dma-sg.c  | 32 +++++++-----
>---
>>> --
>>> drivers/media/common/videobuf2/videobuf2-vmalloc.c | 12 +++----
>>> 3 files changed, 34 insertions(+), 51 deletions(-)
>>>
>>> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
>>> b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
>>> index d3a3ee5..bf31a9d 100644
>>> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
>>> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
>>> @@ -48,16 +48,15 @@ struct vb2_dc_buf {
>>>
>>> static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt)
>>> {
>>> -	struct scatterlist *s;
>>> 	dma_addr_t expected = sg_dma_address(sgt->sgl);
>>> -	unsigned int i;
>>> +	struct sg_dma_page_iter dma_iter;
>>> 	unsigned long size = 0;
>>>
>>> -	for_each_sg(sgt->sgl, s, sgt->nents, i) {
>>> -		if (sg_dma_address(s) != expected)
>>> +	for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
>>> +		if (sg_page_iter_dma_address(&dma_iter) != expected)
>>> 			break;
>>> -		expected = sg_dma_address(s) + sg_dma_len(s);
>>> -		size += sg_dma_len(s);
>>> +		expected += PAGE_SIZE;
>>> +		size += PAGE_SIZE;
>> This code in drm_prime_t_contiguous_size and here.  I seem to remember
>seeing
>> the same pattern in other drivers.
>>
>> Would it worthwhile to make this a helper as well?
>I think I've identified such patterns in all DRM drivers and replaced
>with a common helper. So far I have no idea where to put such helper to
>make it available for media/videobuf2, so those a few lines are indeed
>duplicated here.

I was thinking of drivers outside of DRM/media.  Specifically RDMA.

However, looking at that code, I see that my memory was a little off.
It is working with continuous pages,  but not finding the size.

>> Also, isn't the sg_dma_len() the actual length of the chunk we are looking
>at?
>>
>> If its I not PAGE_SIZE (ie. dma chunk is 4 * PAGE_SIZE?), does your
>loop/calculation still work?
>
>scaterlist page iterators (for_each_sg_page/for_each_sg_dma_page and
>their sgtable variants) always operates on PAGE_SIZE units. They
>correctly handle larger sg_dma_len().

Ahh, ok, I see. 

Thank you!

Mike

>
>Best regards
>--
>Marek Szyprowski, PhD
>Samsung R&D Institute Poland

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Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200512085722eucas1p2fbaab30e49c9ddadc64b27db856e5921@eucas1p2.samsung.com>
2020-05-12  8:57 ` [PATCH v4 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse Marek Szyprowski
     [not found]   ` <CGME20200512090107eucas1p13a38ce5ce4c15cd0033acaea7b26c9b0@eucas1p1.samsung.com>
2020-05-12  9:00     ` [PATCH v4 01/38] dma-mapping: add generic helpers for mapping sgtable objects Marek Szyprowski
     [not found]       ` <CGME20200512090108eucas1p10a3571be3f60265daea3b3f1469b5e82@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 02/38] scatterlist: add generic wrappers for iterating over " Marek Szyprowski
2020-05-13 13:24           ` Robin Murphy
     [not found]       ` <CGME20200512090108eucas1p2168167ab5e1de09df0d5def83f64dbfe@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 03/38] iommu: add generic helper for mapping " Marek Szyprowski
2020-05-13  9:03           ` Joerg Roedel
2020-05-13 13:27           ` Robin Murphy
     [not found]       ` <CGME20200512090109eucas1p285ca10dceb29f43aae1c40814e2dec8d@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 04/38] drm: prime: add common helper to check scatterlist contiguity Marek Szyprowski
     [not found]       ` <CGME20200512090110eucas1p1fdf69509f401e425c45e958430a99b65@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 05/38] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays() Marek Szyprowski
     [not found]       ` <CGME20200512090110eucas1p1b8de7671df480c071718c96f8ebdbc42@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 06/38] drm: core: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090111eucas1p2fd703addaa7975c16a1ea2d7807cc6a6@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 07/38] drm: amdgpu: " Marek Szyprowski
     [not found]       ` <CGME20200512090111eucas1p29897737c262b467437d0775204129105@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 08/38] drm: armada: " Marek Szyprowski
     [not found]       ` <CGME20200512090112eucas1p225de9f54f7fd54346043fc8c31e7ea2d@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 09/38] drm: etnaviv: " Marek Szyprowski
     [not found]       ` <CGME20200512090112eucas1p280707473d14730b8d3054fe9b0781a05@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 10/38] drm: exynos: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200512090113eucas1p254a8b23dd0ee63411df200f66d193203@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 11/38] drm: exynos: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090114eucas1p1917c16e0312cfb191f327e6dad2f7808@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 12/38] drm: i915: " Marek Szyprowski
     [not found]       ` <CGME20200512090114eucas1p1bc4ab112b490205283e7d2f82a9713ee@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 13/38] drm: lima: " Marek Szyprowski
     [not found]       ` <CGME20200512090115eucas1p25e71b29fa935e53e4c04f9b3789a09fc@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 14/38] drm: mediatek: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200512090116eucas1p2089d6eb7aa6bad4d2cbc2875c175873f@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 15/38] drm: mediatek: use common helper for extracting pages array Marek Szyprowski
     [not found]       ` <CGME20200512090116eucas1p24662e01574c0700cfe6d474280bb8df5@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 16/38] drm: msm: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090117eucas1p1acf4ddfe65242d28eee247ab2ca21454@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 17/38] drm: omapdrm: use common helper for extracting pages array Marek Szyprowski
     [not found]       ` <CGME20200512090117eucas1p1179ea62b61b45fae70630e66e434ffb3@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 18/38] drm: omapdrm: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090118eucas1p19ed5cf76c6e1e3f3bcaaefaeff7cf333@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 19/38] drm: panfrost: " Marek Szyprowski
     [not found]       ` <CGME20200512090119eucas1p2c0db485fddf17f15135f8e69e46fc097@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 20/38] drm: radeon: " Marek Szyprowski
     [not found]       ` <CGME20200512090119eucas1p2b3e1a858d8893f8d209d5c19fcbab941@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 21/38] drm: rockchip: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200512090120eucas1p28cc382480b2e3298b59fb6bf5ffde80b@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 22/38] drm: rockchip: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090120eucas1p18ae5489153837bbf5b8baa5089234c40@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 23/38] drm: tegra: " Marek Szyprowski
     [not found]       ` <CGME20200512090121eucas1p2f20e300f70ff54da15fe49cc6690f608@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 24/38] drm: v3d: " Marek Szyprowski
     [not found]       ` <CGME20200512090122eucas1p10cc3f42cb0452a8a279fcc8702e50a7a@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 25/38] drm: virtio: " Marek Szyprowski
     [not found]       ` <CGME20200512090122eucas1p155db33deb51b4bbc34c0a012e4a7361d@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 26/38] drm: vmwgfx: " Marek Szyprowski
     [not found]       ` <CGME20200512090123eucas1p268736ef6e202c23e8be77c56873f415f@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 27/38] xen: gntdev: " Marek Szyprowski
     [not found]       ` <CGME20200512090123eucas1p25758ba07ba913e5a3eeca13c7f386fdb@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 28/38] drm: host1x: " Marek Szyprowski
     [not found]       ` <CGME20200512090124eucas1p1f96fac067834c139fe1095a63b4dc2f0@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 29/38] drm: rcar-du: " Marek Szyprowski
     [not found]       ` <CGME20200512090124eucas1p20509113bdbdd1070d8265aa1af80e64a@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 30/38] dmabuf: " Marek Szyprowski
     [not found]       ` <CGME20200512090125eucas1p1f9eae024a33e92bf1468f2af4e5a1b0a@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 31/38] staging: ion: remove dead code Marek Szyprowski
     [not found]       ` <CGME20200512090126eucas1p1ad8d5dfd09fce31d9a18691a76e9fa75@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 32/38] staging: ion: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200512090127eucas1p19889d83b1c750dcdc869323e8d1946a3@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 33/38] staging: tegra-vde: " Marek Szyprowski
     [not found]       ` <CGME20200512090128eucas1p2cf31bfdca3b096585ba9f2741ef08ce0@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 34/38] misc: fastrpc: " Marek Szyprowski
     [not found]       ` <CGME20200512090128eucas1p11ee8a5e72ca37dc6b3e8a07ea094bab6@eucas1p1.samsung.com>
2020-05-12  9:00         ` [PATCH v4 35/38] rapidio: " Marek Szyprowski
     [not found]       ` <CGME20200512090129eucas1p2e67c8a9adafb202970a59c3412cd887a@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 36/38] samples: vfio-mdev/mbochs: " Marek Szyprowski
     [not found]       ` <CGME20200512090129eucas1p24fa7e83acb8cde494f71ca5694279401@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 37/38] media: pci: fix common ALSA DMA-mapping related codes Marek Szyprowski
     [not found]       ` <CGME20200512090130eucas1p2eb86c5d34be56bbc81032bc0b6927d1e@eucas1p2.samsung.com>
2020-05-12  9:00         ` [PATCH v4 38/38] videobuf2: use sgtable-based scatterlist wrappers Marek Szyprowski
2020-05-12 17:52           ` Ruhl, Michael J
2020-05-12 20:33             ` Marek Szyprowski
2020-05-13 12:01               ` Ruhl, Michael J [this message]
     [not found]       ` <20200512121808.GA20393@lst.de>
2020-05-12 13:00         ` [PATCH v4 01/38] dma-mapping: add generic helpers for mapping sgtable objects Marek Szyprowski
     [not found]           ` <20200512130936.GA24428@lst.de>
2020-05-12 13:19             ` Marek Szyprowski
2020-05-13 13:23       ` Robin Murphy

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