linux-kernel - Re: [PATCH v2 1/3] dmaengine: add new dma API for max_segment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 6 Jun 2011 18:41:09 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	linux@....linux.org.uk
Cc:	fujita.tomonori@....ntt.co.jp, shawn.guo@...aro.org,
	patches@...aro.org, vinod.koul@...el.com, gregkh@...e.de,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	dan.j.williams@...el.com, cjb@...top.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/3] dmaengine: add new dma API for
	max_segment_number

On Mon, 6 Jun 2011 10:14:10 +0100
Russell King - ARM Linux <linux@....linux.org.uk> wrote:

> On Mon, Jun 06, 2011 at 05:06:03PM +0900, FUJITA Tomonori wrote:
> > max_segs isn't unrelated with the dma mapping API. I explained above,
> > IOMMUs doesn't increase the number of segments (could decrease the
> > number of segments by merging).
> > 
> > The limitation about the number of segment already lives elsewhere
> > (e.g. queue's limits.max_segments).
> 
> I think you're missing the point entirely.
> 
> Lets take the problem at hand: you have two devices.  One of them is
> handled by the DMA engine code.  One of them is a block device.
> 
> The block layer needs to know the various parameters of what is
> allowable for DMA, including such things as the maximum size of a
> segment, and the _number_ of segments that can be placed into any
> one request.
> 
> As the DMA provider is _entirely_ separate and unknown to the block
> device driver, the block device driver has no way to sanely provide
> these parameters to the block layer - they are not a property of the
> block device driver, but of the DMA provider.

struct device_dma_parameters is used for a property of the block
device drivers (and scsi HBA drivers, etc). Not DMA provider. Right?

The drivers calls dma_set_seg_boundary() and the subsystems call
dma_get_seg_boundary to set the value to queues.

This patch is trying to use struct device_dma_parameters in a
different way. It adds a new DMA parameter but for the DMA parameter
for a different layer. I'm not sure about different-layer stuff in 
one structure and using similar API.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/