mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: Petr Tesarik <ptesarik@suse.com>
To: Jonathan Corbet <corbet@lwn.net>,
	Randy Dunlap <rdunlap@infradead.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	Bagas Sanjaya <bagasdotme@gmail.com>,
	linux-doc@vger.kernel.org (open list:DOCUMENTATION),
	linux-kernel@vger.kernel.org (open list),
	linux-mm@kvack.org (open list:MEMORY MANAGEMENT),
	Petr Tesarik <ptesarik@suse.com>
Subject: [PATCH v2 8/8] docs: dma-api: clean up documentation of dma_map_sg()
Date: Fri, 27 Jun 2025 12:10:15 +0200	[thread overview]
Message-ID: <20250627101015.1600042-9-ptesarik@suse.com> (raw)
In-Reply-To: <20250627101015.1600042-1-ptesarik@suse.com>

Describe in one sentence what the function does.

Do not repeat example situations when the returned number is lower than
the number of segments on input.

Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
---
 Documentation/core-api/dma-api.rst | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index a075550ebbb54..6a57618118fd4 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -322,10 +322,10 @@ action (e.g. reduce current DMA mapping usage or delay and try again later).
 	dma_map_sg(struct device *dev, struct scatterlist *sg,
 		   int nents, enum dma_data_direction direction)
 
-Returns: the number of DMA address segments mapped (this may be shorter
-than <nents> passed in if some elements of the scatter/gather list are
-physically or virtually adjacent and an IOMMU maps them with a single
-entry).
+Maps a scatter/gather list for DMA. Returns the number of DMA address segments
+mapped, which may be smaller than <nents> passed in if several consecutive
+sglist entries are merged (e.g. with an IOMMU, or if some adjacent segments
+just happen to be physically contiguous).
 
 Please note that the sg cannot be mapped again if it has been mapped once.
 The mapping process is allowed to destroy information in the sg.
@@ -349,9 +349,8 @@ With scatterlists, you use the resulting mapping like this::
 where nents is the number of entries in the sglist.
 
 The implementation is free to merge several consecutive sglist entries
-into one (e.g. with an IOMMU, or if several pages just happen to be
-physically contiguous) and returns the actual number of sg entries it
-mapped them to. On failure 0, is returned.
+into one.  The returned number is the actual number of sg entries it
+mapped them to. On failure, 0 is returned.
 
 Then you should loop count times (note: this can be less than nents times)
 and use sg_dma_address() and sg_dma_len() macros where you previously
-- 
2.49.0


  parent reply	other threads:[~2025-06-27 10:10 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20250627101022eucas1p2f3715c9c9439ca986217e380d4d3e254@eucas1p2.samsung.com>
2025-06-27 10:10 ` [PATCH v2 0/8] update DMA API documentation Petr Tesarik
2025-06-27 10:10   ` [PATCH v2 1/8] docs: dma-api: use "DMA API" consistently throughout the document Petr Tesarik
2025-06-28 18:56     ` Randy Dunlap
2025-06-27 10:10   ` [PATCH v2 2/8] docs: dma-api: replace consistent with coherent Petr Tesarik
2025-06-28 18:57     ` Randy Dunlap
2025-06-27 10:10   ` [PATCH v2 3/8] docs: dma-api: remove remnants of PCI DMA API Petr Tesarik
2025-06-28 18:58     ` Randy Dunlap
2025-06-27 10:10   ` [PATCH v2 4/8] docs: dma-api: add a kernel-doc comment for dma_pool_zalloc() Petr Tesarik
2025-06-28 19:04     ` Randy Dunlap
2025-07-01 11:38       ` Petr Tesarik
2025-07-01 12:54         ` Jonathan Corbet
2025-07-01 15:46           ` Petr Tesarik
2025-06-27 10:10   ` [PATCH v2 5/8] docs: dma-api: remove duplicate description of the DMA pool API Petr Tesarik
2025-06-28 19:01     ` Randy Dunlap
2025-06-27 10:10   ` [PATCH v2 6/8] docs: dma-api: clarify DMA addressing limitations Petr Tesarik
2025-06-28 18:58     ` Randy Dunlap
2025-06-27 10:10   ` [PATCH v2 7/8] docs: dma-api: update streaming DMA physical address constraints Petr Tesarik
2025-06-28 18:59     ` Randy Dunlap
2025-06-30  1:32     ` Bagas Sanjaya
2025-06-27 10:10   ` Petr Tesarik [this message]
2025-06-28 19:00     ` [PATCH v2 8/8] docs: dma-api: clean up documentation of dma_map_sg() Randy Dunlap
2025-06-27 17:03   ` [PATCH v2 0/8] update DMA API documentation Marek Szyprowski
2025-07-01 19:53   ` Jonathan Corbet

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=20250627101015.1600042-9-ptesarik@suse.com \
    --to=ptesarik@suse.com \
    --cc=akpm@linux-foundation.org \
    --cc=axboe@kernel.dk \
    --cc=bagasdotme@gmail.com \
    --cc=corbet@lwn.net \
    --cc=kbusch@kernel.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=m.szyprowski@samsung.com \
    --cc=rdunlap@infradead.org \
    --cc=robin.murphy@arm.com \
    /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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox

all inboxes | Powered by JetHome®