[PATCH v4 0/3] nvmem: migrate to const void * in reg_write

From: Link Mauve <linkmauve@linkmauve.fr>
To: Srinivas Kandagatla <srini@kernel.org>
Cc: "Link Mauve" <linkmauve@linkmauve.fr>,
	"Andy Shevchenko" <andriy.shevchenko@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Kevin Hilman" <khilman@baylibre.com>,
	"Jerome Brunet" <jbrunet@baylibre.com>,
	"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
	"Sven Peter" <sven@kernel.org>, "Janne Grunau" <j@jannau.net>,
	"Neal Gompa" <neal@gompa.dev>, "Frank Li" <Frank.Li@nxp.com>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Vladimir Zapolskiy" <vz@mleia.com>,
	"André Draszik" <andre.draszik@linaro.org>,
	"Orson Zhai" <orsonzhai@gmail.com>,
	"Baolin Wang" <baolin.wang@linux.alibaba.com>,
	"Chunyan Zhang" <zhang.lyra@gmail.com>,
	"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
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	"Kalyani Akula" <kalyani.akula@amd.com>,
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	linux-arm-kernel@lists.infradead.org,
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	asahi@lists.linux.dev, imx@lists.linux.dev,
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	rust-for-linux@vger.kernel.org
Subject: [PATCH v4 0/3] nvmem: migrate to const void * in reg_write
Date: Sun, 26 Jul 2026 15:17:18 +0200	[thread overview]
Message-ID: <20260726131724.15299-1-linkmauve@linkmauve.fr> (raw)

This callback used to take a mutable void * for no reason, which causes
the compiler to be unaware that the val buffer should never be modified
by the callback.

This was found while drafting the nvmem-provider Rust abstraction.

Thanks to the guidance of Andy Shevchenko, this now introduces a new
callback and deprecates the existing one, with the goal of renaming the
new one into the old one once no user remains in the kernel.

Changes since v3:
- Link to v3:
  https://lore.kernel.org/rust-for-linux/20260716142415.28718-1-linkmauve@linkmauve.fr/T/
- Drop Apple SPMI patch, which had already been independently included
  in linux-next as 7089170e1df160f5f8fb395bc5aa2e2697b4e896.
- Reword the cover letter’s subject.
- Reorder the meson firmware patch before the other ones, so that every
  commit is always working correctly.

Changes since v2:
- Link to v2:
  https://lore.kernel.org/rust-for-linux/aljAqBNVXV1aVJqx@luna/T/
- Rebase on top of linux-next/master.
- Fix logic error which made all devices read-only.
- Remove a blanket cast of function pointers to void * in
  apple-spmi-nvmem (patch 3).
- Also fix constness of write buffer in firmware: meson, which is used
  exclusively by meson-efuse (patch 4).
- Re-review all changes to make sure the passed types are more correct
  than they were before.
- Actually test with COMPILE_TEST, which I forgot to enable before…

Changes since v1:
- Link to v1:
  https://lore.kernel.org/rust-for-linux/20260715175229.24672-1-linkmauve@linkmauve.fr/
- Removed all changes to other subsystems than nvmem.
- Added a new reg_write_const callback instead of changing the exisitng
  reg_write.
- Deprecated the existing reg_write callback, it will get removed once
  all users in the kernel will be done migrating to the new one.

Link Mauve (3):
  firmware: meson: pass a const buffer to meson_sm_call_write()
  nvmem: core: deprecate reg_write callback and add reg_write_const
  nvmem: make all reg_write callbacks take const void *

 drivers/firmware/meson/meson_sm.c       |  2 +-
 drivers/nvmem/apple-spmi-nvmem.c        |  4 ++--
 drivers/nvmem/bcm-ocotp.c               |  8 +++----
 drivers/nvmem/core.c                    | 28 ++++++++++++++-----------
 drivers/nvmem/imx-ocotp-scu.c           |  6 +++---
 drivers/nvmem/imx-ocotp.c               |  6 +++---
 drivers/nvmem/internals.h               |  1 +
 drivers/nvmem/lan9662-otpc.c            |  6 +++---
 drivers/nvmem/lpc18xx_eeprom.c          |  6 +++---
 drivers/nvmem/max77759-nvmem.c          |  4 ++--
 drivers/nvmem/meson-efuse.c             |  8 +++----
 drivers/nvmem/qcom-spmi-sdam.c          |  6 +++---
 drivers/nvmem/qfprom.c                  |  6 +++---
 drivers/nvmem/rave-sp-eeprom.c          |  6 +++---
 drivers/nvmem/snvs_lpgpr.c              |  4 ++--
 drivers/nvmem/sprd-efuse.c              |  6 +++---
 drivers/nvmem/stm32-bsec-optee-ta.c     |  2 +-
 drivers/nvmem/stm32-bsec-optee-ta.h     |  4 ++--
 drivers/nvmem/stm32-romem.c             | 10 ++++-----
 drivers/nvmem/zynqmp_nvmem.c            |  6 +++---
 include/linux/firmware/meson/meson_sm.h |  2 +-
 include/linux/nvmem-provider.h          |  6 +++++-
 22 files changed, 73 insertions(+), 64 deletions(-)

base-commit: 9eebf259d5352b87080d67758f483583d9e763d7
-- 
2.55.0

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