[PATCH v2 0/2] nvmem: fix a const-unsoundness in reg_write

From: Link Mauve <linkmauve@linkmauve.fr>
To: Srinivas Kandagatla <srini@kernel.org>
Cc: "Link Mauve" <linkmauve@linkmauve.fr>,
	"Andy Shevchenko" <andy@kernel.org>,
	"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>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Kevin Hilman" <khilman@baylibre.com>,
	"Jerome Brunet" <jbrunet@baylibre.com>,
	"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
	"Orson Zhai" <orsonzhai@gmail.com>,
	"Baolin Wang" <baolin.wang@linux.alibaba.com>,
	"Chunyan Zhang" <zhang.lyra@gmail.com>,
	"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
	"Alexandre Torgue" <alexandre.torgue@foss.st.com>,
	"Kalyani Akula" <kalyani.akula@amd.com>,
	"Michal Simek" <michal.simek@amd.com>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Boqun Feng" <boqun@kernel.org>, "Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <lossin@kernel.org>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"Daniel Almeida" <daniel.almeida@collabora.com>,
	"Tamir Duberstein" <tamird@kernel.org>,
	"Alexandre Courbot" <acourbot@nvidia.com>,
	"Onur Özkan" <work@onurozkan.dev>,
	asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, imx@lists.linux.dev,
	linux-amlogic@lists.infradead.org, linux-arm-msm@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	rust-for-linux@vger.kernel.org
Subject: [PATCH v2 0/2] nvmem: fix a const-unsoundness in reg_write
Date: Wed, 15 Jul 2026 21:55:16 +0200	[thread overview]
Message-ID: <20260715195520.25410-1-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 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 (2):
  nvmem: core: deprecate reg_write callback and add reg_write_const
  nvmem: make all reg_write callbacks take const void *

 drivers/nvmem/apple-spmi-nvmem.c    |  2 +-
 drivers/nvmem/bcm-ocotp.c           |  6 +++---
 drivers/nvmem/core.c                | 26 +++++++++++++++++---------
 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         |  6 +++---
 drivers/nvmem/qcom-spmi-sdam.c      |  4 ++--
 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/nvmem-provider.h      |  6 +++++-
 20 files changed, 68 insertions(+), 55 deletions(-)

-- 
2.55.0

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