From: Jonathan Corbet <corbet@lwn.net>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: 'Russell King - ARM Linux' <linux@arm.linux.org.uk>,
Michal Nazarewicz <m.nazarewicz@samsung.com>,
linux-mm@kvack.org, 'Daniel Walker' <dwalker@codeaurora.org>,
Pawel Osciak <p.osciak@samsung.com>,
'Mark Brown' <broonie@opensource.wolfsonmicro.com>,
linux-kernel@vger.kernel.org,
'Hiremath Vaibhav' <hvaibhav@ti.com>,
'FUJITA Tomonori' <fujita.tomonori@lab.ntt.co.jp>,
'Kyungmin Park' <kyungmin.park@samsung.com>,
'Zach Pfeffer' <zpfeffer@codeaurora.org>,
linux-media@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCHv2 2/4] mm: cma: Contiguous Memory Allocator added
Date: Tue, 27 Jul 2010 06:58:42 -0600 [thread overview]
Message-ID: <20100727065842.40ae76c8@bike.lwn.net> (raw)
In-Reply-To: <003701cb2d89$adae4580$090ad080$%szyprowski@samsung.com>
On Tue, 27 Jul 2010 14:45:58 +0200
Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> > How does one obtain the CPU address of this memory in order for the CPU
> > to access it?
>
> Right, we did not cover such case. In CMA approach we tried to separate
> memory allocation from the memory mapping into user/kernel space. Mapping
> a buffer is much more complicated process that cannot be handled in a
> generic way, so we decided to leave this for the device drivers. Usually
> video processing devices also don't need in-kernel mapping for such
> buffers at all.
Still...that *is* why I suggested an interface which would return both
the DMA address and a kernel-space virtual address, just like the DMA
API does... Either that, or just return the void * kernel address and
let drivers do the DMA mapping themselves. Returning only the
dma_addr_t address will make the interface difficult to use in many
situations.
jon
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next prev parent reply other threads:[~2010-07-27 12:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-26 14:11 [PATCHv2 0/4] The Contiguous Memory Allocator Michal Nazarewicz
2010-07-26 14:11 ` [PATCHv2 1/4] lib: rbtree: rb_root_init() function added Michal Nazarewicz
2010-07-26 14:11 ` [PATCHv2 2/4] mm: cma: Contiguous Memory Allocator added Michal Nazarewicz
2010-07-26 14:11 ` [PATCHv2 3/4] mm: cma: Test device and application added Michal Nazarewicz
2010-07-26 14:11 ` [PATCHv2 4/4] arm: Added CMA to Aquila and Goni Michal Nazarewicz
2010-07-26 20:28 ` [PATCHv2 2/4] mm: cma: Contiguous Memory Allocator added Hans Verkuil
2010-07-27 7:41 ` Marek Szyprowski
2010-07-27 16:27 ` Hans Verkuil
2010-07-28 9:04 ` Marek Szyprowski
2010-08-01 13:26 ` Hans Verkuil
2010-08-02 15:51 ` Michał Nazarewicz
2010-08-03 7:19 ` Hans Verkuil
2010-08-06 13:31 ` Michał Nazarewicz
2010-07-27 12:08 ` Russell King - ARM Linux
2010-07-27 12:45 ` Marek Szyprowski
2010-07-27 12:58 ` Jonathan Corbet [this message]
2010-07-27 13:46 ` Marek Szyprowski
2010-07-27 14:21 ` FUJITA Tomonori
2010-07-28 8:53 ` Michał Nazarewicz
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