[PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API

[Laurent Pinchart]

On Tue, Jun 13, 2023 at 07:31:46PM +0000, Biju Das wrote:
> > Subject: RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
> > > Subject: RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
> > > > Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
> > > >
> > > > Hi everyone,
> > > >
> > > > > Perhaps we should first think through what an ancillary device
> > > > > really is.  My understanding is that it is used to talk to
> > > > > secondary addresses of a multi-address I2C slave device.
> > > >
> > > > As I mentioned somewhere before, this is not the case. Ancillary
> > > > devices are when one *driver* handles more than one address.
> > > > Everything else has been handled differently in the past (for  all
> > > > the uses I am aware of).
> > > >
> > > > Yet, I have another idea which is so simple that I wonder if it
> > > > maybe has already been discussed so far?
> > > >
> > > > * have two regs in the bindings
> > >
> > > OK, it is inline with DT maintainers expectation as it is matching
> > > with real hw as single device node having two regs.
> > >
> > > > * use the second reg with i2c_new_client_device to instantiate the
> > > >   RTC sibling. 'struct i2c_board_info', which is one parameter, should
> > > >   have enough options to pass data, e.g it has a software_node.
> > >
> > > OK, I can see the below can be passed from PMIC to new client device.
> > >
> > > 	client->addr = info->addr;
> > >
> > > 	client->init_irq = info->irq;
> > >
> > > >
> > > > Should work or did I miss something here?
> > >
> > > I guess it will work. We instantiate appropriate device based On PMIC
> > > revision and slave address and IRQ resource passed through 'struct
> > > i2c_board_info'
> > >
> > > Will check this and update you.
> > 
> > info.irq = irq; -->Irq fine
> > info.addr = addr; -->slave address fine
> > size = strscpy(info.type, name, sizeof(info.type)); -->instantiation based
> > on PMIC version fine.
> > 
> > 1) How do we share clk details on instantiated device to find is it
> > connected to external crystal or external clock source? as we cannot pass
> > of_node between PMIC and "i2c_board_info" as it results in pinctrl
> > failure. info->platformdata and
> > Client->dev.platformdata to retrieve this info??
> 
> Or 
> 
> I2C instantiation based on actual oscillator bit value, ie, two i2c_device_id's
> with one for setting oscillator bit and another for clearing oscillator bit
> 
> PMIC driver parses the clock details. Based on firmware version and clock, 
> It instantiates either i2c_device_id with setting oscillator bit or
> clearing oscillator bit.

I don't like that hack. I still think that two DT nodes is the best
option, I think you're trying hard to hack around a problem that is
actually not a problem.

-- 
Regards,

Laurent Pinchart