[U-Boot-Users] PATCH: Add command support for second I2C controller

Ben Warren bwarren at qstreams.com
Tue May 16 17:34:45 CEST 2006


This approach sounds good.  The only down-side that I can see is that
the driver needs to keep track of context.  Personally, I prefer
self-contained code whenever possible, but in this case your approach is

In order to do this properly, we should add to the base API in
include/i2c.h something like:

void i2c_set_bus(uchar dev);
uchar i2c_get_bus(void);
void i2c_set_bus_speed(int speed);
int i2c_get_bus_speed(void);

or merge the index and speed as you have in your code.

The drivers can then either choose to implement or not implement this
feature, and we can add a parallel command tree based on 'i2c' as
Wolfgang has suggested.



On Tue, 2006-05-16 at 10:10 -0500, Menon, Nishanth wrote:
> Hi Ben,
> Some reasons why I am against the approach of giving i2c bus along with
> the command itself:
> 1. Cannot handle scenarios of HS controllers.
> 2. cmd_i2c is a debug interface, once a bus is selected, we would like
> to do read and write operations to a specific chip. To repeat the bus
> number all the time is a overhead. 
> 3. To a smaller extent, older users need to be aware of the change
> involved.
> 4. a simpler and lesser intrusive implementation adding an additional
> command to select bus can achieve the same functionality. (I send a
> previous mail with this).
> > Attached is a patch to common/cmd_i2c.c that allows access to two I2C
> > controllers on a board.  Note that this doesn't actually change any
> 5. importantly, common/cmd_i2c.c is a bad place to limit i2c busses..
> each board/.. file should be given the functionality.
> Regards,
> Nishanth Menon

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