From: Arnd Bergmann <arnd@arndb.de>
To: Jordan Crouse <jcrouse@codeaurora.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
'Subash Patel' <subashrp@gmail.com>,
linux-arch@vger.kernel.org,
'Russell King - ARM Linux' <linux@arm.linux.org.uk>,
'Joerg Roedel' <joro@8bytes.org>,
linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
'Kyungmin Park' <kyungmin.park@samsung.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [Linaro-mm-sig] [PATCH/RFC 0/8] ARM: DMA-mapping framework redesign
Date: Fri, 24 Jun 2011 17:20:15 +0200 [thread overview]
Message-ID: <201106241720.15385.arnd@arndb.de> (raw)
In-Reply-To: <4E02119F.4000901@codeaurora.org>
On Wednesday 22 June 2011, Jordan Crouse wrote:
> >> I have a query in similar lines, but related to user virtual address
> >> space. Is it feasible to extend these DMA interfaces(and IOMMU), to map
> >> a user allocated buffer into the hardware?
> >
> > This can be done with the current API, although it may not look so
> > straightforward. You just need to create a scatter list of user pages
> > (these can be gathered with get_user_pages function) and use dma_map_sg()
> > function. If the dma-mapping support iommu, it can map all these pages
> > into a single contiguous buffer on device (DMA) address space.
> >
> > Some additional 'magic' might be required to get access to pages that are
> > mapped with pure PFN (VM_PFNMAP flag), but imho it still can be done.
> >
> > I will try to implement this feature in videobuf2-dma-config allocator
> > together with the next version of my patches for dma-mapping&iommu.
>
> With luck DMA_ATTRIB_NO_KERNEL_MAPPING should remove any lingering arguments
> for trying to map user pages. Given that our ultimate goal here is buffer
> sharing, user allocated pages have limited value and appeal. If anything, I
> vote that this be a far lower priority compared to the rest of the win you
> have here.
I agree. Mapping user-allocated buffers is extremely hard to get right
when there are extra constraints. If it doesn't work already for some driver,
I wouldn't put too much effort into making it work for more special cases.
Arnd
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WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Jordan Crouse <jcrouse@codeaurora.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
'Subash Patel' <subashrp@gmail.com>,
linux-arch@vger.kernel.org,
'Russell King - ARM Linux' <linux@arm.linux.org.uk>,
'Joerg Roedel' <joro@8bytes.org>,
linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
'Kyungmin Park' <kyungmin.park@samsung.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [Linaro-mm-sig] [PATCH/RFC 0/8] ARM: DMA-mapping framework redesign
Date: Fri, 24 Jun 2011 17:20:15 +0200 [thread overview]
Message-ID: <201106241720.15385.arnd@arndb.de> (raw)
Message-ID: <20110624152015.3J_3mmDIiLMp_rQKRrJm78CAFg3ar3lqwA6_b-iQl-4@z> (raw)
In-Reply-To: <4E02119F.4000901@codeaurora.org>
On Wednesday 22 June 2011, Jordan Crouse wrote:
> >> I have a query in similar lines, but related to user virtual address
> >> space. Is it feasible to extend these DMA interfaces(and IOMMU), to map
> >> a user allocated buffer into the hardware?
> >
> > This can be done with the current API, although it may not look so
> > straightforward. You just need to create a scatter list of user pages
> > (these can be gathered with get_user_pages function) and use dma_map_sg()
> > function. If the dma-mapping support iommu, it can map all these pages
> > into a single contiguous buffer on device (DMA) address space.
> >
> > Some additional 'magic' might be required to get access to pages that are
> > mapped with pure PFN (VM_PFNMAP flag), but imho it still can be done.
> >
> > I will try to implement this feature in videobuf2-dma-config allocator
> > together with the next version of my patches for dma-mapping&iommu.
>
> With luck DMA_ATTRIB_NO_KERNEL_MAPPING should remove any lingering arguments
> for trying to map user pages. Given that our ultimate goal here is buffer
> sharing, user allocated pages have limited value and appeal. If anything, I
> vote that this be a far lower priority compared to the rest of the win you
> have here.
I agree. Mapping user-allocated buffers is extremely hard to get right
when there are extra constraints. If it doesn't work already for some driver,
I wouldn't put too much effort into making it work for more special cases.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [Linaro-mm-sig] [PATCH/RFC 0/8] ARM: DMA-mapping framework redesign
Date: Fri, 24 Jun 2011 17:20:15 +0200 [thread overview]
Message-ID: <201106241720.15385.arnd@arndb.de> (raw)
In-Reply-To: <4E02119F.4000901@codeaurora.org>
On Wednesday 22 June 2011, Jordan Crouse wrote:
> >> I have a query in similar lines, but related to user virtual address
> >> space. Is it feasible to extend these DMA interfaces(and IOMMU), to map
> >> a user allocated buffer into the hardware?
> >
> > This can be done with the current API, although it may not look so
> > straightforward. You just need to create a scatter list of user pages
> > (these can be gathered with get_user_pages function) and use dma_map_sg()
> > function. If the dma-mapping support iommu, it can map all these pages
> > into a single contiguous buffer on device (DMA) address space.
> >
> > Some additional 'magic' might be required to get access to pages that are
> > mapped with pure PFN (VM_PFNMAP flag), but imho it still can be done.
> >
> > I will try to implement this feature in videobuf2-dma-config allocator
> > together with the next version of my patches for dma-mapping&iommu.
>
> With luck DMA_ATTRIB_NO_KERNEL_MAPPING should remove any lingering arguments
> for trying to map user pages. Given that our ultimate goal here is buffer
> sharing, user allocated pages have limited value and appeal. If anything, I
> vote that this be a far lower priority compared to the rest of the win you
> have here.
I agree. Mapping user-allocated buffers is extremely hard to get right
when there are extra constraints. If it doesn't work already for some driver,
I wouldn't put too much effort into making it work for more special cases.
Arnd
next prev parent reply other threads:[~2011-06-24 15:20 UTC|newest]
Thread overview: 201+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-20 7:50 [PATCH/RFC 0/8] ARM: DMA-mapping framework redesign Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 1/8] ARM: dma-mapping: remove offset parameter to prepare for generic dma_ops Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 8:35 ` Michal Nazarewicz
2011-06-20 8:35 ` Michal Nazarewicz
2011-06-20 8:35 ` Michal Nazarewicz
2011-06-20 10:46 ` Marek Szyprowski
2011-06-20 10:46 ` Marek Szyprowski
2011-06-20 10:46 ` Marek Szyprowski
2011-07-03 15:28 ` Russell King - ARM Linux
2011-07-03 15:28 ` Russell King - ARM Linux
2011-07-03 15:28 ` Russell King - ARM Linux
2011-07-26 12:56 ` Marek Szyprowski
2011-07-26 12:56 ` Marek Szyprowski
2011-07-26 12:56 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 2/8] ARM: dma-mapping: implement dma_map_single on top of dma_map_page Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 14:39 ` Russell King - ARM Linux
2011-06-20 14:39 ` Russell King - ARM Linux
2011-06-20 14:39 ` Russell King - ARM Linux
2011-06-20 15:15 ` Marek Szyprowski
2011-06-20 15:15 ` Marek Szyprowski
2011-06-20 15:15 ` Marek Szyprowski
2011-06-24 15:24 ` Arnd Bergmann
2011-06-24 15:24 ` Arnd Bergmann
2011-06-24 15:24 ` Arnd Bergmann
2011-06-27 14:29 ` Marek Szyprowski
2011-06-27 14:29 ` Marek Szyprowski
2011-06-27 14:29 ` Marek Szyprowski
2011-06-27 14:53 ` Arnd Bergmann
2011-06-27 14:53 ` Arnd Bergmann
2011-06-27 14:53 ` Arnd Bergmann
2011-06-27 15:06 ` Marek Szyprowski
2011-06-27 15:06 ` Marek Szyprowski
2011-06-27 15:06 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 3/8] ARM: dma-mapping: use asm-generic/dma-mapping-common.h Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 14:33 ` [Linaro-mm-sig] " KyongHo Cho
2011-06-20 14:33 ` KyongHo Cho
2011-06-20 14:33 ` KyongHo Cho
2011-06-21 11:47 ` Marek Szyprowski
2011-06-21 11:47 ` Marek Szyprowski
2011-06-21 11:47 ` Marek Szyprowski
2011-06-24 8:39 ` 'Joerg Roedel'
2011-06-24 8:39 ` 'Joerg Roedel'
2011-06-24 8:39 ` 'Joerg Roedel'
2011-06-24 15:36 ` Arnd Bergmann
2011-06-24 15:36 ` Arnd Bergmann
2011-06-24 15:36 ` Arnd Bergmann
2011-06-24 15:36 ` Arnd Bergmann
2011-06-27 12:18 ` Marek Szyprowski
2011-06-27 12:18 ` Marek Szyprowski
2011-06-27 12:18 ` Marek Szyprowski
2011-06-27 13:19 ` Arnd Bergmann
2011-06-27 13:19 ` Arnd Bergmann
2011-06-27 13:19 ` Arnd Bergmann
2011-07-07 12:09 ` Lennert Buytenhek
2011-07-07 12:09 ` Lennert Buytenhek
2011-07-07 12:09 ` Lennert Buytenhek
2011-07-07 12:38 ` Russell King - ARM Linux
2011-07-07 12:38 ` Russell King - ARM Linux
2011-07-07 12:38 ` Russell King - ARM Linux
2011-07-15 0:10 ` Lennert Buytenhek
2011-07-15 0:10 ` Lennert Buytenhek
2011-07-15 0:10 ` Lennert Buytenhek
2011-07-15 9:27 ` Russell King - ARM Linux
2011-07-15 9:27 ` Russell King - ARM Linux
2011-07-15 9:27 ` Russell King - ARM Linux
2011-07-15 21:53 ` Lennert Buytenhek
2011-07-15 21:53 ` Lennert Buytenhek
2011-07-15 21:53 ` Lennert Buytenhek
2011-06-20 7:50 ` [PATCH 4/8] ARM: dma-mapping: implement dma sg methods on top of generic dma ops Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 14:37 ` KyongHo Cho
2011-06-20 14:37 ` KyongHo Cho
2011-06-20 14:37 ` KyongHo Cho
2011-06-20 14:40 ` Russell King - ARM Linux
2011-06-20 14:40 ` Russell King - ARM Linux
2011-06-20 14:40 ` Russell King - ARM Linux
2011-06-20 15:23 ` Marek Szyprowski
2011-06-20 15:23 ` Marek Szyprowski
2011-06-20 15:23 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 5/8] ARM: dma-mapping: move all dma bounce code to separate dma ops structure Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 14:42 ` Russell King - ARM Linux
2011-06-20 14:42 ` Russell King - ARM Linux
2011-06-20 14:42 ` Russell King - ARM Linux
2011-06-20 15:31 ` Marek Szyprowski
2011-06-20 15:31 ` Marek Szyprowski
2011-06-20 15:31 ` Marek Szyprowski
2011-06-24 15:47 ` Arnd Bergmann
2011-06-24 15:47 ` Arnd Bergmann
2011-06-24 15:47 ` Arnd Bergmann
2011-06-27 14:20 ` Marek Szyprowski
2011-06-27 14:20 ` Marek Szyprowski
2011-06-27 14:20 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 6/8] ARM: dma-mapping: remove redundant code and cleanup Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 7/8] common: dma-mapping: change alloc/free_coherent method to more generic alloc/free_attrs Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 14:45 ` KyongHo Cho
2011-06-20 14:45 ` KyongHo Cho
2011-06-20 14:45 ` KyongHo Cho
2011-06-20 15:06 ` Russell King - ARM Linux
2011-06-20 15:06 ` Russell King - ARM Linux
2011-06-20 15:06 ` Russell King - ARM Linux
2011-06-20 15:06 ` Russell King - ARM Linux
2011-06-20 15:14 ` [Linaro-mm-sig] " KyongHo Cho
2011-06-20 15:14 ` KyongHo Cho
2011-06-20 15:14 ` KyongHo Cho
2011-06-21 11:23 ` Marek Szyprowski
2011-06-21 11:23 ` Marek Szyprowski
2011-06-21 11:23 ` Marek Szyprowski
2011-06-22 0:00 ` [Linaro-mm-sig] " KyongHo Cho
2011-06-22 0:00 ` KyongHo Cho
2011-06-22 0:00 ` KyongHo Cho
2011-06-24 7:20 ` Marek Szyprowski
2011-06-24 7:20 ` Marek Szyprowski
2011-06-24 7:20 ` Marek Szyprowski
2011-06-24 15:51 ` Arnd Bergmann
2011-06-24 15:51 ` Arnd Bergmann
2011-06-24 15:51 ` Arnd Bergmann
2011-06-24 16:15 ` James Bottomley
2011-06-24 16:15 ` James Bottomley
2011-06-24 16:15 ` James Bottomley
2011-06-24 16:23 ` Arnd Bergmann
2011-06-24 16:23 ` Arnd Bergmann
2011-06-24 16:23 ` Arnd Bergmann
2011-06-27 12:23 ` Marek Szyprowski
2011-06-27 12:23 ` Marek Szyprowski
2011-06-27 12:23 ` Marek Szyprowski
2011-06-27 12:23 ` Marek Szyprowski
2011-06-27 13:22 ` Arnd Bergmann
2011-06-27 13:22 ` Arnd Bergmann
2011-06-27 13:22 ` Arnd Bergmann
2011-06-27 13:30 ` Marek Szyprowski
2011-06-27 13:30 ` Marek Szyprowski
2011-06-27 13:30 ` Marek Szyprowski
2011-06-24 15:53 ` Arnd Bergmann
2011-06-24 15:53 ` Arnd Bergmann
2011-06-24 15:53 ` Arnd Bergmann
2011-06-27 14:41 ` Marek Szyprowski
2011-06-27 14:41 ` Marek Szyprowski
2011-06-27 14:41 ` Marek Szyprowski
2011-06-20 7:50 ` [PATCH 8/8] ARM: dma-mapping: use alloc, mmap, free from dma_ops Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-20 7:50 ` Marek Szyprowski
2011-06-22 6:53 ` [Linaro-mm-sig] " KyongHo Cho
2011-06-22 6:53 ` KyongHo Cho
2011-06-22 6:53 ` KyongHo Cho
2011-06-22 4:53 ` [Linaro-mm-sig] [PATCH/RFC 0/8] ARM: DMA-mapping framework redesign Subash Patel
2011-06-22 4:53 ` Subash Patel
2011-06-22 4:53 ` Subash Patel
2011-06-22 6:59 ` Marek Szyprowski
2011-06-22 6:59 ` Marek Szyprowski
2011-06-22 6:59 ` Marek Szyprowski
2011-06-22 8:53 ` Subash Patel
2011-06-22 8:53 ` Subash Patel
2011-06-22 8:53 ` Subash Patel
2011-06-22 9:27 ` Marek Szyprowski
2011-06-22 9:27 ` Marek Szyprowski
2011-06-22 9:27 ` Marek Szyprowski
2011-06-22 16:00 ` Jordan Crouse
2011-06-22 16:00 ` Jordan Crouse
2011-06-22 16:00 ` Jordan Crouse
2011-06-23 13:09 ` Subash Patel
2011-06-23 13:09 ` Subash Patel
2011-06-23 13:09 ` Subash Patel
2011-06-23 16:24 ` Michael K. Edwards
2011-06-23 16:24 ` Michael K. Edwards
2011-06-23 16:24 ` Michael K. Edwards
2011-06-23 22:09 ` Michael K. Edwards
2011-06-23 22:09 ` Michael K. Edwards
2011-06-23 22:09 ` Michael K. Edwards
2011-06-25 5:23 ` Jonathan Morton
2011-06-25 5:23 ` Jonathan Morton
2011-06-25 5:23 ` Jonathan Morton
2011-06-25 9:55 ` Michael K. Edwards
2011-06-25 9:55 ` Michael K. Edwards
2011-06-25 9:55 ` Michael K. Edwards
2011-06-26 0:06 ` Jonathan Morton
2011-06-26 0:06 ` Jonathan Morton
2011-06-26 0:06 ` Jonathan Morton
2011-06-24 15:20 ` Arnd Bergmann [this message]
2011-06-24 15:20 ` Arnd Bergmann
2011-06-24 15:20 ` Arnd Bergmann
2011-06-24 9:18 ` Joerg Roedel
2011-06-24 9:18 ` Joerg Roedel
2011-06-24 9:18 ` Joerg Roedel
2011-06-24 14:26 ` Marek Szyprowski
2011-06-24 14:26 ` Marek Szyprowski
2011-06-24 14:26 ` Marek Szyprowski
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