[PATCH v6 0/3] hwmon: (ads7871) Fix endianness and modernize driver

Tabrez Ahmed
2026-05-02T02:08:53Z

This patch series addresses a critical endianness issue in the ads7871
hardware monitoring driver and updates the driver to use the modern
hwmon API.

The series is broken down as follows:
- Patch 1: Fixes corrupted voltage readings on Big-Endian architectures
by safely converting the 16-bit sensor output using le16_to_cpu().
- Patch 2: Modernizes the driver by migrating it from the deprecated
hwmon API to hwmon_device_register_with_info().
- Patch 3: Ensures all SPI write operations use a properly allocated,
DMA-safe buffer.

Note: I do not have access to the physical ADS7871 hardware. This
series has been compile-tested only.

Changes in v6:
- patch 1:
- Switched back to using spi_w8r16() combined with le16_to_cpu()
for the endian conversion, removing the manual byte array.
- Added an early return for negative error codes from the SPI core
to prevent mangling the error status before conversion.
- Dropped the now-unused <linux/unaligned.h> header.
- patches 2 & 3:
- Unchanged from v5.

Changes in v5:
- Fixed a bisectability issue where the <linux/unaligned.h> include
modernization was accidentally squashed into Patch 3 instead of Patch 1.

Changes in v4:
- Patch 1: Refactored 16-bit register reads to use a dedicated 'u8'
transmit variable, eliminating a 32-bit pointer endianness hazard.

Changes in v3:
- Added Patch 1 to fix the pre-existing endianness bug in 16-bit reads.
- Fixed multiple formatting and alignment issues caught by checkpatch
--strict, as requested by Guenter Roeck.
- Added "While at it, fix checkpatch violations" to Patch 2 commit message.

Changes in v2:
- Dropped custom mutex in favor of native hwmon core serialization.
- Split API migration and DMA fix into separate, logical patches.
- Corrected output scaling and sign extension to meet hwmon ABI.

Tabrez Ahmed (3):
hwmon: (ads7871) Fix endianness bug in 16-bit register reads
hwmon: (ads7871) Convert to hwmon_device_register_with_info
hwmon: (ads7871) Use DMA-safe buffer for SPI writes

drivers/hwmon/ads7871.c | 115 +++++++++++++++++++++++-----------------
1 file changed, 65 insertions(+), 50 deletions(-)

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2.43.0