[PATCH 0/6] dmaengine: Add common dma_slave_config and split it into src and dst parts

[Frank Li <Frank.Li@nxp.com>]

Many DMA engine drivers store a dma_slave_config per channel. Propagate
this configuration into struct dma_chan to avoid duplicating the same
code in each driver.

Much of dma_slave_config is identical for source and destination. Split
the configuration into src and dst groups and use a union to preserve
backward compatibility. This reduces the need for drivers to repeatedly
check the DMA transfer direction.

This change introduces the general approach. If this method is accepted,
more drivers can be updated incrementally.

Looking ahead, this also enables improvements to the vchan
implementation. Most DMA engines follow one of two descriptor models:

  - Cyclic hardware buffers (e.g. dw-edma)
  - Linked-list descriptors (e.g. fsl-edma)

 *
 *       ┌──────┐    ┌──────┐    ┌──────┐
 *       │      │ ┌─►│      │ ┌─►│      │
 *       │      │ │  │      │ │  │      │
 *       ├──────┤ │  ├──────┤ │  ├──────┤
 *       │ Next ├─┘  │ Next ├─┘  │ Next │
 *       └──────┘    └──────┘    └──────┘

A large portion of the software logic is shared between these models.
Recent work already shares circular buffer handling between eDMA and
HDMA [1], and this can be extended to support more hardware.

Ultimately, a DMA engine should only need to implement logic to fill a
single list item.

[1] https://lore.kernel.org/dmaengine/aWTyGpGN6WqtVCfN@ryzen/T/#t

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Frank Li (6):
      dmaengine: Move struct dma_chan after struct dma_slave_config
      dmaengine: Add common slave configuration to dma_chan
      dmaengine: fsl-edma: use dma_chan common config
      dmaengine: imx-sdma: use common config at dma_chan
      dmaengine: Add union and dma_slave_get_config() helper for dma_slave_config
      dmaengine: fsl-edma: use common dma_slave_get_cfg()

 drivers/dma/fsl-edma-common.c | 141 +++++++++++++++++------------------
 drivers/dma/fsl-edma-common.h |   1 -
 drivers/dma/imx-sdma.c        |   8 +-
 include/linux/dmaengine.h     | 166 +++++++++++++++++++++++++-----------------
 4 files changed, 166 insertions(+), 150 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20260112-dma_common_config-cb87b461296f

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