I2C host adapter slave support

I2C host adapter slave support

[Chandra shekhar]

Hi,

I am implementing i2c slave mode transfers, and found out that there isn't really any support in the subsystem for this.
Also I did not find any discussions regarding this in i2c mailing list. 
Are there any discussions or plans about implementing host adapter slave support in i2c subsytem?


Regards,
Chandra Shekhar

Re: I2C host adapter slave support

[Nishanth Menon]

Chandra shekhar wrote:
> I am implementing i2c slave mode transfers, and found out that there isn't really any support in the subsystem for this.
> Also I did not find any discussions regarding this in i2c mailing list. 
> Are there any discussions or plans about implementing host adapter slave support in i2c subsytem?
>   
Not true on many counts: google is a good search engine :): 
http://www.google.com/search?hl=en&q=i2c+slave+support+linux

one thread of interest is:
http://lists.lm-sensors.org/pipermail/i2c/2007-April/001027.html
Quote">/ > Russell King has added I2C slave support at least for PXA... 
/I'm curious. How does it work? Does this means that there is no need 
for cooperation from i2c-core to implement I2C slave support in I2C bus 
drivers? Or is i2c-pxa implementing things which should be moved to 
i2c-core? This discussion probably belongs to a different thread though, 
I doesn't seem to be related to bus speed issues at all. "

Finally see the slave implementation here:
http://www.gelato.unsw.edu.au/lxr/source/drivers/i2c/busses/i2c-pxa.c
Regards,
Nishanth Menon

Re: I2C host adapter slave support

[Chandra shekhar]

 
> Chandra shekhar wrote:
> > I am implementing i2c slave mode transfers, and found out 
> that there isn't really any support in the subsystem for this.
> > Also I did not find any discussions regarding this in i2c 
> mailing list. 
> > Are there any discussions or plans about implementing host 
> adapter slave support in i2c subsytem?
> >   
> one thread of interest is:
> http://lists.lm-sensors.org/pipermail/i2c/2007-April/001027.html

This is more related to opearting speed for i2c devices sitting on a common bus.


> Quote">/ > Russell King has added I2C slave support at least 
> for PXA... 
> /I'm curious. How does it work? Does this means that there is 
> no need for cooperation from i2c-core to implement I2C slave 
> support in I2C bus drivers? Or is i2c-pxa implementing things 
> which should be moved to i2c-core? 

Precisely,  this is my question. If we were to support slave mode there should be
Some callback or hooks to trigger upper layer app. after receive operations, which 
Ideally should be part of i2c-core I think. 
I am yet to look at i2c-pxa code.


This discussion probably 
> belongs to a different thread though, I doesn't seem to be 
> related to bus speed issues at all. "
> 
> Finally see the slave implementation here:
> http://www.gelato.unsw.edu.au/lxr/source/drivers/i2c/busses/i2c-pxa.c
> Regards,
> Nishanth Menon
> 

Re: I2C host adapter slave support

[Nishanth Menon]

Chandra shekhar wrote:
>  
>   
>> one thread of interest is:
>> http://lists.lm-sensors.org/pipermail/i2c/2007-April/001027.html
>>     
>
> This is more related to opearting speed for i2c devices sitting on a common bus.
>
>   
True, there is a side discussion on slave support
> Precisely,  this is my question. If we were to support slave mode there should be
> Some callback or hooks to trigger upper layer app. after receive operations, which 
> Ideally should be part of i2c-core I think. 
> I am yet to look at i2c-pxa code.
You have not been reading too detailed in to the thread and not looked 
at the code:
"http://lists.lm-sensors.org/pipermail/i2c/2007-April/001049.html:
:) this driver is compile time slave/master. Now, I have an i2c 
controller which is capable of master /slave - ofcourse only one at a 
time for one controller instance. But, I have n instances of the same. 
Each capable of being slave or master based on board. The framework wont 
let me do it unless I create two drivers - one for slave and other for 
master - define separate adapters for them.. Not exactly efficient, but 
could work. Can we do this with a cleaner support from i2c-core(like 
able to write a single adapter driver which can be used as both 
slave/master based ofcourse on board defns)? Maybe a seperate thread of 
discussion?
"
So I guess this is that thread of discussion.

Gist:
a) you can implement i2c slave adapter support today with the existing 
framework
b) my conjecture at the time of discussion was that "to have the same 
driver to handle master and slave in a build might need further changes"

Regards,
Nishanth Menon


Regards,
Nishanth Menon