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From: Christoph Hellwig <hch@lst.de>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Christoph Hellwig <hch@lst.de>, Tomasz Figa <tfiga@chromium.org>,
	Robin Murphy <robin.murphy@arm.com>, Anle Pan <anle.pan@nxp.com>,
	m.szyprowski@samsung.com, mchehab@kernel.org,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	hui.fang@nxp.com
Subject: Re: [PATCH] media: videobuf2-dma-sg: limit the sg segment size
Date: Thu, 31 Aug 2023 14:35:32 +0200	[thread overview]
Message-ID: <20230831123532.GA11156@lst.de> (raw)
In-Reply-To: <ZO9xzf727b/YvZB/@ziepe.ca>

On Wed, Aug 30, 2023 at 01:43:57PM -0300, Jason Gunthorpe wrote:
> > > conversion function for the drivers.
> > 
> > Jason said at LSF/MM that he had a prototype for a mapping API that
> > takes a phys/len array as input and dma_addr/len a output, which really
> > is the right thing to do, especially for dmabuf.
> 
> Yes, still a prototype. Given the change in direction some of the
> assumptions of the list design will need some adjusting.
> 
> I felt there wasn't much justification to add a list without also
> supporting the P2P and it was not looking very good to give the DMA
> API proper p2p support without also connecting it to lists somehow.
> 
> Anyhow, I had drafted a basic list datastructure and starting
> implementation that is sort of structured in away that is similar to
> xarray (eg with fixed chunks, generic purpose, etc)
> 
> https://github.com/jgunthorpe/linux/commit/58d7e0578a09d9cd2360be515208bcd74ade5958

This seems fairly complicated complicated, and the entry seems pretty large
for a bio_vec replacement or a dma_addr_t+len tuple, which both should
be (sizeof(phys_addr_t) + sizeof(u32) + the size of flags if needed, which
for 64-bit would fit into the padding from 96 bytes to 128 bytes anyway.

  reply	other threads:[~2023-08-31 12:35 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-28  7:54 [PATCH] media: videobuf2-dma-sg: limit the sg segment size Anle Pan
2023-08-29 10:03 ` Tomasz Figa
2023-08-29 11:14   ` Robin Murphy
2023-08-29 15:04     ` Christoph Hellwig
2023-08-30  3:47       ` Tomasz Figa
2023-08-30 14:33         ` Christoph Hellwig
2023-08-30 16:43           ` Jason Gunthorpe
2023-08-31 12:35             ` Christoph Hellwig [this message]
2023-08-31 15:32               ` Jason Gunthorpe
2023-09-01  6:10                 ` Christoph Hellwig
2023-09-01 14:26                   ` Jason Gunthorpe
     [not found]       ` <DB9PR04MB92841D8BC1122D5A4210F78987E6A@DB9PR04MB9284.eurprd04.prod.outlook.com>
2023-08-30 13:41         ` [EXT] " Robin Murphy
2023-08-30  3:59     ` Tomasz Figa
2023-09-06  8:52     ` Hans Verkuil
2023-09-06  9:26       ` Tomasz Figa
2023-09-06  9:43         ` Hans Verkuil
2023-08-30  8:50 ` Hui Fang
2023-08-30  9:28   ` Tomasz Figa
2023-09-04  7:10     ` [EXT] " Hui Fang
2023-09-05  3:43       ` Tomasz Figa
2023-09-06  8:16         ` Hui Fang
2023-09-06  9:28           ` Tomasz Figa
2023-09-11  6:13             ` Hui Fang
2023-09-12  2:22               ` Tomasz Figa
2023-09-12  7:01                 ` Hui Fang
2023-09-12  7:10                   ` Tomasz Figa
2023-09-12  7:43                     ` Hui Fang
2023-09-12  7:51                       ` Tomasz Figa
2023-09-13  9:13                         ` Hui Fang
2023-09-13  9:44                           ` Tomasz Figa
2023-09-13 13:16                             ` Hui Fang
2023-09-18  2:28                               ` Hui Fang

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