All of lore.kernel.org
 help / color / mirror / Atom feed
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

WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Tejun Heo <tj@kernel.org>
Cc: Shuah Khan <shuah.kh@samsung.com>,
	Eli Billauer <eli.billauer@gmail.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 16:12:11 +0200	[thread overview]
Message-ID: <20140604141211.GC23880@8bytes.org> (raw)
In-Reply-To: <20140604140408.GC5004@htj.dyndns.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



  parent reply	other threads:[~2014-06-04 14:12 UTC|newest]

Thread overview: 29+ 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
2014-06-01  7:01   ` Eli Billauer
2014-06-03 21:24   ` Shuah Khan
     [not found]     ` <538E3D04.9060808-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2014-06-03 23:39       ` Joerg Roedel
2014-06-03 23:39         ` Joerg Roedel
2014-06-04 14:04         ` Tejun Heo
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 14:12               ` Joerg Roedel
2014-06-04 14:14               ` Tejun Heo
2014-06-04 14:14                 ` Tejun Heo
2014-06-04 15:03                 ` Eli Billauer
2014-06-04 15:03                   ` Eli Billauer
     [not found]                   ` <538F3548.4050101-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-06-04 21:25                     ` Joerg Roedel
2014-06-04 21:25                       ` Joerg Roedel
     [not found]                       ` <20140604212525.GE23880-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2014-06-06 11:45                         ` Eli Billauer
2014-06-06 11:45                           ` Eli Billauer
     [not found]                           ` <5391A9C2.3040602-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-06-06 16:01                             ` Greg KH
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 16:21                                   ` Eli Billauer
2014-06-06 17:02                                   ` Shuah Khan
2014-06-07 11:23                                     ` Eli Billauer
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   ` 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20140604141211.GC23880@8bytes.org \
    --to=joro-zlv9swrftaidnm+yrofe0a@public.gmane.org \
    --cc=bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
    --cc=devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org \
    --cc=discuss-Wa75r+71Mmgdnm+yROfE0A@public.gmane.org \
    --cc=eli.billauer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
    --cc=gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org \
    --cc=iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \
    --cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=shuah.kh-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org \
    --cc=tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.