i2c: slave-eeprom: update documentation

Add more details which have either been missing ever since or describe
recent additions.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: NLuca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

Documentation/i2c/slave-eeprom-backend.rst

 ==============================
-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.

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