From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org,
Shuah Khan <shuah.kh-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
discuss-Wa75r+71Mmgdnm+yROfE0A@public.gmane.org,
gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org,
Eli Billauer
<eli.billauer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single()
Date: Wed, 4 Jun 2014 16:12:11 +0200 [thread overview]
Message-ID: <20140604141211.GC23880@8bytes.org> (raw)
In-Reply-To: <20140604140408.GC5004-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
On Wed, Jun 04, 2014 at 10:04:08AM -0400, Tejun Heo wrote:
> Hmmm? Don't we have drivers which map dma buffers on device init and
> release them on exit? For dynamic usages, its usefulness is limited
> especially given that dynamic tracking of buffers usually would
> involve tracking of other information too in addition to dma buffer
> pointer themselves. If alloc on init and free on exit is a very rare
> usage pattern, I have no objection against not adding devm interface
> for dma mappings.
Yes, but those drivers usually get DMA buffers at init time with the
dma_alloc_* interfaces. The dma_map_* interfaces discussed here belong
to the streaming DMA-API, so they are usually used for only one DMA
transaction before dma_unmap_* is called on them.
A devm interface for the dma_alloc_* family of functions would
actually make sense, but not for the dma_map_* functions.
Joerg
next prev parent reply other threads:[~2014-06-04 14:12 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
[not found] ` <538E3D04.9060808-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2014-06-03 23:39 ` Joerg Roedel
2014-06-04 14:04 ` Tejun Heo
[not found] ` <20140604140408.GC5004-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2014-06-04 14:12 ` Joerg Roedel [this message]
2014-06-04 14:14 ` Tejun Heo
2014-06-04 15:03 ` Eli Billauer
[not found] ` <538F3548.4050101-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-06-04 21:25 ` Joerg Roedel
[not found] ` <20140604212525.GE23880-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2014-06-06 11:45 ` Eli Billauer
[not found] ` <5391A9C2.3040602-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-06-06 16:01 ` Greg KH
[not found] ` <20140606160103.GG15110-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
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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