On Thu, Sep 18, 2008 at 6:13 PM, Sebastian Siewior
[off-list ref] wrote:

* Ayman El-Khashab | 2008-09-18 14:44:44 [-0500]:

quoted

Here is a snippet from the dts file, and I assume I need something like
what I've added:

                       IIC0: i2c@ef600700 {
                               compatible = "ibm,iic-460ex", "ibm,iic";
                               reg = <ef600700 14>;
                               interrupt-parent = <&UIC0>;
                               interrupts = <2 4>;
                               #address-cells = <1>;
                               #size-cells = <0>;
                               rtc@68 {
                                       compatible = "stm,m41t80";
                                       reg = <68>;
                               };
                               eeprom@50 {
                                       compatible = "?????";
                                                  something
                                       something;
                               };

This should look like:
|                        IIC0: i2c@ef600700 {
|                                compatible = "ibm,iic-460ex", "ibm,iic";
|                                reg = <ef600700 14>;
|                                interrupt-parent = <&UIC0>;
|                                interrupts = <2 4>;
|                                #address-cells = <1>;
|                                #size-cells = <0>;
|                                rtc@68 {
|                                        compatible = "m41t80";
|                                        reg = <68>;
|                                };
|                                eeprom@50 {
|                                        compatible = "eeprom";

The new eeprom driver is at24, eeprom is the old one. at24 has write support.

EEPROMs from most vendors (AT24)

Enable this driver to get read/write support to most I2C EEPROMs,
after you configure the driver to know about each EEPROM on
your target board. Use these generic chip names, instead of
vendor-specific ones like at24c64 or 24lc02:

24c00, 24c01, 24c02, spd (readonly 24c02), 24c04, 24c08,
24c16, 24c32, 24c64, 24c128, 24c256, 24c512, 24c1024

Unless you like data loss puzzles, always be sure that any chip
you configure as a 24c32 (32 kbit) or larger is NOT really a
24c16 (16 kbit) or smaller, and vice versa. Marking the chip
as read-only won't help recover from this. Also, if your chip
has any software write-protect mechanism you may want to review the
code to make sure this driver won't turn it on by accident.

If you use this with an SMBus adapter instead of an I2C adapter,
full functionality is not available. Only smaller devices are
supported (24c16 and below, max 4 kByte).

This driver can also be built as a module. If so, the module
will be called at24.

|                                        reg = <50>;
|                                };

Compatible is the ID of the driver. You can find it in the driver
itself: if you look in ./drivers/rtc/rtc-m41t80.c you will find a struct
m41t80_id which contains the ids. The same applies to the eeprom driver.
You might want to update your dts from current kernel tree which
contains the "/dts-v1/" tag at the beginning and then your field must
contain an 0x prefix.

quoted

Once I do all that, how does one use the eeprom driver to read and write
this part?

The eeprom driver should create an eeprom file somewhere in /sys I am
not sure where exactly. The help entry in Kconfig says that is module
provides only RO access to the eeprom.

Sebastian
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