[U-Boot] [PATCH v2 0/17] dm: Add I2C support and convert sandbox, tegra

[Masahiro Yamada]

Hi Simon,



On Tue, 11 Nov 2014 10:46:16 -0700
Simon Glass <sjg at chromium.org> wrote:

> 
> This series adds I2C support to driver model. It has become apparent that
> this is a high priority as it is widely used. It follows along to some
> extent from the SPI conversion.
> 
> Several changes are made from the original I2C implementations.
> 
> Firstly it is not necessary to specify the chip address with every call,
> since each chip knows its own address - it is stored in struct dm_i2c_chip
> which is attached to each chip on the I2C bus. However, this information
> *is* passed to the driver since I presume most drivers need it and it would
> be cumbersome to look up in every call.
> 
> Secondly there is no concept of a 'current' I2C bus so all associated logic
> is removed. With driver model i2c_set_bus_num() and i2c_get_bus_num() are
> not available. Since the chip device specifies both the bus and the chip
> address, there is no need for this concept. It also causes problems when
> one driver changes the current bus and forgets to change it back.
> 
> Thirdly initialisation is handled by driver model's normal probe() method
> on each device so there should be no need for i2c_init_all(), i2c_init(),
> i2c_init_board(), i2c_board_late_init() and board_i2c_init().
> 
> I2C muxes are not yet supported. To support these we will need to maintain
> state of the current mux settings to avoid resetting every mux every time.
> Probably we need to add a sandbox I2C mux driver to permit testing of this.
> This can probably be done later.
> 
> Platform data is not yet supported either, only device tree. The

This statement implies that platform data will (should) be supported
in the future, I think.

As you know, I have a strong belief that device tree should be left optional.

If platform data is supported someday, that's OK.



Best Regards
Masahiro Yamada