[PATCH 0/6] spi: add multi-CS and per-transfer lane mask support

[Jonathan Santos <Jonathan.Santos@analog.com>]

This series introduces two SPI subsystem features: per-transfer chipselect
masks and multi-CS device support. Together they address the multi-device
setup described in [1] and the limitation noted in [2], where no SPI
controller completely handles logical chip selects beyond the first one.

The first part of the set addresses multi-CS support. Some SPI controllers
can assert multiple chip selects simultaneously, but the existing code
hardcoded CS index 0 in both spi_set_cs() and of_spi_parse_dt(),
preventing this from working.

The second part addresses dynamic lane selection for STRIPE mode. In
SPI_MULTI_LANE_MODE_STRIPE, all available lanes are currently always
active. Some peripherals need to select a different subset of rx/tx lanes
per transfer. New fields are added to the spi_transfer struct to allow
drivers to specify which lanes to use for each transfer. The documentation
is also updated to describe this new behavior.

[1]: https://lore.kernel.org/linux-iio/af0EGv172ZMl%2F6N5@JSANTO12-L01.ad.analog.com/T/#t
[2]: https://lore.kernel.org/all/20250915183725.219473-1-jonas.gorski@gmail.com/

Jonathan Santos (6):
  spi: support simultaneous assertion of multiple CS
  spi: add per-transfer CS mask
  spi: spi-engine-ex: Add support for multi-CS devices
  spi: Documentation: multiple-data-lanes: describe rx and tx lane mask
  spi: add rx and tx lane mask to spi_transfer struct
  spi: axi-spi-engine: add support for dynamic multi-lane selection

 Documentation/spi/multiple-data-lanes.rst |  30 ++++++
 drivers/spi/spi-axi-spi-engine.c          | 106 +++++++++++++++++-----
 drivers/spi/spi.c                         |  97 +++++++++++++++++---
 include/linux/spi/spi.h                   |  12 +++
 4 files changed, 206 insertions(+), 39 deletions(-)


base-commit: 093239070573637ad2b4cb56abc9c4c7ee109294
-- 
2.34.1