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SubjectRe: [RFC PATCH 1/3] eeprom: Add a simple EEPROM framework


On 20/02/15 17:21, Rob Herring wrote:
> On Thu, Feb 19, 2015 at 11:08 AM, Srinivas Kandagatla
> <srinivas.kandagatla@linaro.org> wrote:
>> From: Maxime Ripard <maxime.ripard@free-electrons.com>
>>
>> Up until now, EEPROM drivers were stored in drivers/misc, where they all had to
>> duplicate pretty much the same code to register a sysfs file, allow in-kernel
>> users to access the content of the devices they were driving, etc.
>>
>> This was also a problem as far as other in-kernel users were involved, since
>> the solutions used were pretty much different from on driver to another, there
>> was a rather big abstraction leak.
>>
>> This introduction of this framework aims at solving this. It also introduces DT
>> representation for consumer devices to go get the data they require (MAC
>> Addresses, SoC/Revision ID, part numbers, and so on) from the EEPROMs.
>>
>> Having regmap interface to this framework would give much better
>> abstraction for eeproms on different buses.
>>
>> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>> [srinivas.kandagatla: Moved to regmap based and cleanedup apis]
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>> .../devicetree/bindings/eeprom/eeprom.txt | 48 ++++
>> drivers/Kconfig | 2 +
>> drivers/Makefile | 1 +
>> drivers/eeprom/Kconfig | 19 ++
>> drivers/eeprom/Makefile | 9 +
>> drivers/eeprom/core.c | 290 +++++++++++++++++++++
>> include/linux/eeprom-consumer.h | 73 ++++++
>> include/linux/eeprom-provider.h | 51 ++++
>
> Who is going to be the maintainer for this?

Am happy to be one.

>
>> 8 files changed, 493 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/eeprom/eeprom.txt
>> create mode 100644 drivers/eeprom/Kconfig
>> create mode 100644 drivers/eeprom/Makefile
>> create mode 100644 drivers/eeprom/core.c
>> create mode 100644 include/linux/eeprom-consumer.h
>> create mode 100644 include/linux/eeprom-provider.h
>>
>> diff --git a/Documentation/devicetree/bindings/eeprom/eeprom.txt b/Documentation/devicetree/bindings/eeprom/eeprom.txt
>> new file mode 100644
>> index 0000000..9ec1ec2
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/eeprom/eeprom.txt
>
> Please make bindings a separate patch.
Sure, Will do it in next version.

>
>> @@ -0,0 +1,48 @@
>> += EEPROM Data Device Tree Bindings =
>> +
>> +This binding is intended to represent the location of hardware
>> +configuration data stored in EEPROMs.
>> +
>> +On a significant proportion of boards, the manufacturer has stored
>> +some data on an EEPROM-like device, for the OS to be able to retrieve
>> +these information and act upon it. Obviously, the OS has to know
>> +about where to retrieve these data from, and where they are stored on
>> +the storage device.
>> +
>> +This document is here to document this.
>> +
>> += Data providers =
>> +
>> +Required properties:
>> +#eeprom-cells: Number of cells in an eeprom specifier; The common
>> + case is 2.
>
> We already have eeproms in DTs, it would be nice to be able to support
> them with this framework as well.

Yes, I can see more than 60% of them are atmel,at24* eeproms in DT. We
have some plans to migrate at24 and at25 eeproms to this framework once
the the framework itself is accepted.

>
>> +
>> +For example:
>> +
>> + at24: eeprom@42 {
>> + #eeprom-cells = <2>;
>> + };
>> +
>> += Data consumers =
>> +
>> +Required properties:
>> +
>> +eeproms: List of phandle and data cell specifier triplet, one triplet
>> + for each data cell the device might be interested in. The
>> + triplet consists of the phandle to the eeprom provider, then
>> + the offset in byte within that storage device, and the length
>> + in byte of the data we care about.
>
> The problem with this is it assumes you know who the consumer is and
> that it is a DT node. For example, how would you describe a serial
> number?
Correct me if I miss understood.
Is serial number any different?
Am hoping that the eeprom consumer would be aware of offset and size of
serial number in the eeprom

Cant the consumer do:

eeprom-consumer {
eeproms = <&at24 0 4>;
eeprom-names = "device-serial-number";
};

--srini

>
> Rob
>


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