i2c: slave-eeprom: update documentation

Add more details which have either been missing ever since or describe
recent additions.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/Documentation/i2c/slave-eeprom-backend.rst b/Documentation/i2c/slave-eeprom-backend.rst
index 0b8cd83698e0f00d944c08f174a266ff93720b4f..38d951f103023a4637b2d7110886148f2af00b8a 100644 (file)
--- a/Documentation/i2c/slave-eeprom-backend.rst
+++ b/Documentation/i2c/slave-eeprom-backend.rst
@@ -1,14 +1,26 @@
 ==============================
-Linux I2C slave eeprom backend
+Linux I2C slave EEPROM backend
 ==============================
 
-by Wolfram Sang <wsa@sang-engineering.com> in 2014-15
+by Wolfram Sang <wsa@sang-engineering.com> in 2014-20
 
-This is a proof-of-concept backend which acts like an EEPROM on the connected
-I2C bus. The memory contents can be modified from userspace via this file
-located in sysfs::
+This backend simulates an EEPROM on the connected I2C bus. Its memory contents
+can be accessed from userspace via this file located in sysfs::
 
        /sys/bus/i2c/devices/<device-directory>/slave-eeprom
 
+The following types are available: 24c02, 24c32, 24c64, and 24c512. Read-only
+variants are also supported. The name needed for instantiating has the form
+'slave-<type>[ro]'. Examples follow:
+
+24c02, read/write, address 0x64:
+  # echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-1/new_device
+
+24c512, read-only, address 0x42:
+  # echo slave-24c512ro 0x1042 > /sys/bus/i2c/devices/i2c-1/new_device
+
+You can also preload data during boot if a device-property named
+'firmware-name' contains a valid filename (DT or ACPI only).
+
 As of 2015, Linux doesn't support poll on binary sysfs files, so there is no
 notification when another master changed the content.

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index ef39c83aaf337a89ba6c1aa48dcb3f82cca374c2..6e2d0d2531c5238f73e04bc2674759d904c8c36b 100644 (file)
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -118,6 +118,9 @@ if I2C_SLAVE
 
 config I2C_SLAVE_EEPROM
        tristate "I2C eeprom slave driver"
+       help
+         This backend makes Linux behave like an I2C EEPROM. Please read
+         Documentation/i2c/slave-eeprom-backend.rst for further details.
 
 endif