linux-kernel - [PATCH v4 0/4] iio: adc: ad9467: Support alternative backends

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Message-Id: <20260121-b4-ad9467-optional-backend-v4-0-18d2c0d450cc@vaisala.com>
Date: Wed, 21 Jan 2026 12:08:29 +0000
From: Tomas Melin <tomas.melin@...sala.com>
To: Michael Hennerich <Michael.Hennerich@...log.com>, 
 Nuno Sa <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Andy Shevchenko <andy@...nel.org>, 
 Olivier Moysan <olivier.moysan@...s.st.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Tomas Melin <tomas.melin@...sala.com>
Subject: [PATCH v4 0/4] iio: adc: ad9467: Support alternative backends

To facilitate backends with different set of features, add support
for defining capabilites provided by the backend. These capabilites
typically extend beyond a single operation and are therefore not
directly linked to if a single function call is implemented or not.
Furthermore, the capabilites determine if a certain set of operations
should be attempted, or skipped by the frontend. This way
the frontend driver can work with a minimalistic set of features and
still have the device in fully functional state.

Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
---
Changes in v4:
- Readd CAP_BUFFERING and also add CAP_ALWAYS_ON to support backends
  that do not need explicit enable/disable
- Don't mix checks for eopnotsupp and caps. Prefer capability checking
  also for caps that map to single operation
- Move capability checking to top of call stack
- Revise iio_backend_has_caps to use bool signature and fixup semantics
- Amend documentation texts
- Add capability checks for axi-dac
- Drop two's complement patch from this series, already applied
- Link to v3: https://lore.kernel.org/r/20260114-b4-ad9467-optional-backend-v3-0-d2c84979d010@vaisala.com

Changes in v3:
- Reduce set of capabilities to only include calibration. The other
  ones propsed in V2 can be seen as subset of calibration, or single
  operation failing with opnotsupported
- Rename backends checking function
- Relocate caps field inside backend struct (pahole)
- Add kernel-docs
- Add capabilites for exisiting backend variants
- Link to v2: https://lore.kernel.org/r/20260113-b4-ad9467-optional-backend-v2-0-0a27e7e72f41@vaisala.com

Changes in v2:
- Added industrialio-backend capabilities feature
- Removed acceptance for fully optional backend, instead require atleast
  minimalistic backend to exist
- Switched to FIELD_MODIFY()
- Fixed kernel test robot reported failure for missing bitfield.h
- Link to v1: https://lore.kernel.org/r/20251216-b4-ad9467-optional-backend-v1-0-83e61531ef4d@vaisala.com

---
Tomas Melin (4):
      iio: industrialio-backend: support backend capabilities
      iio: adc: adi-axi-adc: define supported iio-backend capabilities
      iio: adc: adi-axi-dac: define supported iio-backend capabilities
      iio: adc: ad9467: check for backend capabilities

 drivers/iio/adc/ad9467.c           | 72 ++++++++++++++++++++++++--------------
 drivers/iio/adc/adi-axi-adc.c      |  3 ++
 drivers/iio/dac/adi-axi-dac.c      |  2 ++
 drivers/iio/industrialio-backend.c | 16 +++++++++
 include/linux/iio/backend.h        | 25 +++++++++++++
 5 files changed, 91 insertions(+), 27 deletions(-)
---
base-commit: a7b10f0963c651a6406d958a5f64b9c5594f84da
change-id: 20251215-b4-ad9467-optional-backend-23f1099ee4d7

Best regards,
-- 
Tomas Melin <tomas.melin@...sala.com>