linux-kernel - [PATCH v2 0/3] Add control driver for ST M24LR RFID/NFC EEPROM chips

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Message-ID: <20250601153022.2027919-1-abd.masalkhi@gmail.com>
Date: Sun,  1 Jun 2025 15:30:18 +0000
From: Abd-Alrhman Masalkhi <abd.masalkhi@...il.com>
To: linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Cc: arnd@...db.de,
	gregkh@...uxfoundation.org,
	robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	abd.masalkhi@...il.com
Subject: [PATCH v2 0/3] Add control driver for ST M24LR RFID/NFC EEPROM chips

This patch series adds support for the control interface of STMicroelectronics 
M24LR RFID/NFC EEPROM devices, such as the M24LR04E-R. The chip exposes two 
I2C addresses and two distinct address spaces: one for the system parameter 
sector and another for the EEPROM memory. These address spaces overlap (both
start at address 0). Due to this overlap, the chip cannot be represented by a
single Device Tree node and handled by the standard at24 driver.

While it might be possible to model the system parameter sector and EEPROM
as two separate DT nodes, each handled by the standard at24 driver, this
leads to synchronization problems. For example, if a multi-page EEPROM write
is in progress and a control command (e.g., a i2c write lock) is issued
concurrently, it can result in incomplete or inconsistent writeing.

To overcome these issues, while maintaining a clean architecture and ensuring
synchronization, the chip is managed by two drivers:

1- The first driver exposes the system parameter sector and acts as an I2C mux
   (gate) for EEPROM access. Using an I2C mux solves the synchronization issue.
   This patch series implements this driver.
2- The second is the standard at24 driver, which handles the EEPROM.

Tested on: M24LR04E-R using Yocto on Raspberry Pi 4

Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@...il.com>

Abd-Alrhman Masalkhi (3):
  dt-bindings: eeprom: Add ST M24LR control interface
  misc: add sysfs control driver for ST M24LR series RFID/NFC chips
  ABI: sysfs: document control attributes for ST M24LR

 .../testing/sysfs-bus-i2c-devices-m24lr_ctl   |  96 +++
 .../devicetree/bindings/eeprom/st,m24lr.yaml  |  72 ++
 drivers/misc/Kconfig                          |  15 +
 drivers/misc/Makefile                         |   1 +
 drivers/misc/m24lr_ctl.c                      | 677 ++++++++++++++++++
 5 files changed, 861 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-i2c-devices-m24lr_ctl
 create mode 100644 Documentation/devicetree/bindings/eeprom/st,m24lr.yaml
 create mode 100644 drivers/misc/m24lr_ctl.c

-- 
2.43.0