From: Joerg Roedel <joro@8bytes.org>
To: Eli Billauer <eli.billauer@gmail.com>
Cc: Tejun Heo <tj@kernel.org>, Shuah Khan <shuah.kh@samsung.com>,
devel@driverdev.osuosl.org, gregkh@linuxfoundation.org,
bhelgaas@google.com, linux-kernel@vger.kernel.org,
linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org,
discuss@x86-64.org
Subject: Re: [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single()
Date: Wed, 4 Jun 2014 23:25:25 +0200 [thread overview]
Message-ID: <20140604212525.GE23880@8bytes.org> (raw)
In-Reply-To: <538F3548.4050101@gmail.com>
Hi,
On Wed, Jun 04, 2014 at 06:03:36PM +0300, Eli Billauer wrote:
> I believe that I need a managed dma_map_single() my own driver,
> which doesn't fall in the case of a single use: The driver allocates
> its buffers with __get_free_pages() (or the to-be managed version of
> it). Then it cuts the allocated memory into smaller buffers (in some
> cases, and with certain alignment rules), and then calls
> dma_map_single() to do the DMA mapping for each. The buffers are
> held along the driver's lifetime, with DMA sync API juggling control
> back and forth to the hardware. Note that the DMA is noncoherent.
What you are trying to do should work with dma_alloc_noncoherent(). The
API allows partial syncs on this memory, so you should be fine.
The problem with a devm variant of dma_map_* is that it is too easy to
misuse or to use it wrong so that a driver could eat up all available
DMA handles on some platforms.
Joerg
next prev parent reply other threads:[~2014-06-04 21:25 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-01 7:01 [PATCH v2 0/4] devres: dma-mapping: Introducing new functions Eli Billauer
2014-06-01 7:01 ` [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single() Eli Billauer
2014-06-03 21:24 ` Shuah Khan
2014-06-03 23:39 ` Joerg Roedel
2014-06-04 14:04 ` Tejun Heo
2014-06-04 14:12 ` Joerg Roedel
2014-06-04 14:14 ` Tejun Heo
2014-06-04 15:03 ` Eli Billauer
2014-06-04 21:25 ` Joerg Roedel [this message]
2014-06-06 11:45 ` Eli Billauer
2014-06-06 16:01 ` Greg KH
2014-06-06 16:21 ` Eli Billauer
2014-06-06 17:02 ` Shuah Khan
2014-06-07 11:23 ` Eli Billauer
2014-06-01 7:01 ` [PATCH v2 2/4] dma-mapping: Add devm_ interface for dma_map_single_attrs() Eli Billauer
2014-06-01 7:01 ` [PATCH v2 3/4] dma-mapping: pci: Add devm_ interface for pci_map_single Eli Billauer
2014-06-01 7:01 ` [PATCH v2 4/4] staging: xillybus: Use devm_ API for memory allocation and DMA mapping Eli Billauer
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