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[v4,0/4] dmaengine: rename dma_chan::dev to dma_chan::chan_dev for clarity

Message ID 20260909-dma-chan_dev-rename-v4-0-d8fb6892a70f@nxp.com (mailing list archive)
Headers
Series dmaengine: rename dma_chan::dev to dma_chan::chan_dev for clarity |

Message

Frank Li Sept. 9, 2026, 4:22 p.m. UTC 
The current dma_chan structure contains both "device" and "dev". So

    chan->device->dev refers to the DMA engine device.
    chan->dev->device refers to the per-channel device instance.

Their similar naming makes the distinction unclear and increases reader
confusion.

Add union dma_chan::chan_dev to make its purpose explicit and clearly
identify it as the per-channel device. After all user switch to chan_dev,
union and dma_chan::dev will be removed.

Update the kernel-doc accordingly. Besides its sysfs usage, the per-channel
device is also used by some DMA engine drivers for IOMMU mapping and
therefore deserves a more accurate description.

1st patch add help vchan_chan_name()
2nd patch use existing helper dma_chan_name() to reduce rename difference.
3rd patch add (dmaengine|vchan)_chan_dev() helper
4th patch add union chan_dev for dma_chan::dev for clarity

Need following patch to clean other dma engineer driver, which is not
in drivers/dma

After complete all rename work, dma_chan::dev can be removed.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v4:
- move some args to previous line to reduce LOC
- s/iommu/IOMMU
- fix multi-line comments at patch4
- collect reviewed-by tags
- Link to v3: https://patch.msgid.link/20260904-dma-chan_dev-rename-v3-0-685601b0b788@nxp.com

Changes in v3:
- add new helper function dmaengine_chan_dev() and vchan_chan_dev() to
make clear.
- some reduntant error message will be addressed by new patches.
- Link to v2: https://patch.msgid.link/20260903-dma-chan_dev-rename-v2-0-0db305b6c716@nxp.com

Changes in v2:
- rebase to dmaengine/next
- add vchan_chan_name() help function for vchan case.
- Link to v1: https://patch.msgid.link/20260812-dma-chan_dev-rename-v1-0-a67131f7d5c2@nxp.com

---
Frank Li (4):
      dmaengine: vchan: add vchan_chan_name() to get channel device name
      dmaengine: use dma_chan_name() helper to get per-channel device name
      dmaengine: add (dmaengine|vchan)_chan_dev() helper
      dmaengine: add union chan_dev for dma_chan::dev for clarity

 drivers/dma/arm-dma350.c                       |   2 +-
 drivers/dma/at_hdmac.c                         |  81 ++++++-------
 drivers/dma/at_xdmac.c                         | 159 ++++++++++++-------------
 drivers/dma/dma-jz4780.c                       |  10 +-
 drivers/dma/dmaengine.c                        |  34 +++---
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c |  39 +++---
 drivers/dma/dw-axi-dmac/dw-axi-dmac.h          |  10 --
 drivers/dma/dw/core.c                          |  47 ++++----
 drivers/dma/ep93xx_dma.c                       |  37 +++---
 drivers/dma/idma64.c                           |  10 +-
 drivers/dma/loongson/loongson1-apb-dma.c       |  23 ++--
 drivers/dma/loongson/loongson2-apb-cmc-dma.c   |  17 +--
 drivers/dma/loongson/loongson2-apb-dma.c       |   9 +-
 drivers/dma/mmp_pdma.c                         |   3 +-
 drivers/dma/moxart-dma.c                       |  23 ++--
 drivers/dma/nbpfaxi.c                          |   2 +-
 drivers/dma/owl-dma.c                          |  21 ++--
 drivers/dma/pch_dma.c                          |  41 +++----
 drivers/dma/pxa_dma.c                          |  52 ++++----
 drivers/dma/st_fdma.c                          |   2 +-
 drivers/dma/ste_dma40.c                        |  15 +--
 drivers/dma/stm32/stm32-dma.c                  |  69 +++++------
 drivers/dma/stm32/stm32-dma3.c                 |  99 ++++++++-------
 drivers/dma/stm32/stm32-mdma.c                 |  96 +++++++--------
 drivers/dma/sun4i-dma.c                        |  17 +--
 drivers/dma/sun6i-dma.c                        |  31 ++---
 drivers/dma/switchtec_dma.c                    |  14 +--
 drivers/dma/tegra186-gpc-dma.c                 |   4 +-
 drivers/dma/tegra20-apb-dma.c                  |   2 +-
 drivers/dma/ti/k3-udma.c                       |   6 +-
 drivers/dma/timb_dma.c                         |  63 +++++-----
 drivers/dma/txx9dmac.c                         |  73 ++++++------
 drivers/dma/virt-dma.h                         |  16 +++
 include/linux/dmaengine.h                      |  23 +++-
 include/trace/events/tegra_apb_dma.h           |   6 +-
 35 files changed, 538 insertions(+), 618 deletions(-)
---
base-commit: a5f8e3471fc20567df888267885dec3eb340eb37
change-id: 20260812-dma-chan_dev-rename-66263ac5eac9

Best regards,
--  
Frank Li <Frank.Li@nxp.com>

Comments

Vinod Koul Sept. 15, 2026, 5:36 p.m. UTC | #1 
On Wed, 09 Sep 2026 12:22:27 -0400, Frank.Li@oss.nxp.com wrote:
> The current dma_chan structure contains both "device" and "dev". So
> 
>     chan->device->dev refers to the DMA engine device.
>     chan->dev->device refers to the per-channel device instance.
> 
> Their similar naming makes the distinction unclear and increases reader
> confusion.
> 
> [...]

Applied, thanks!

[1/4] dmaengine: vchan: add vchan_chan_name() to get channel device name
      commit: 75d8640d7f5f89d1a1c39ccb72166ada95fb38d2
[2/4] dmaengine: use dma_chan_name() helper to get per-channel device name
      commit: 76574306c1ac38137683c69407f0e7810f407e4d
[3/4] dmaengine: add (dmaengine|vchan)_chan_dev() helper
      commit: 3b97a3ec420542591c10db8600cf481f1038a011
[4/4] dmaengine: add union chan_dev for dma_chan::dev for clarity
      commit: 6ad1b49cc30dc9bc7c06dd44241e61fe6f82c0b8

Best regards,