linux-kernel - Re: [PATCH 15/27] regulator: fan53555: Export I2C module alias information

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Date:	Tue, 04 Aug 2015 12:08:40 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	Javier Martinez Canillas <javier@....samsung.com>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/27] regulator: fan53555: Export I2C module alias
 information

Hi Javier,

On ma, 2015-08-03 at 16:29 +0200, Javier Martinez Canillas wrote:
> On 08/03/2015 01:43 PM, Paul Bolle wrote:
> > On do, 2015-07-30 at 18:18 +0200, Javier Martinez Canillas wrote:

> I2C is a little special in that it uses the id_table again to match
> in i2c_device_probe() and pass a i2c_device_id to the I2C driver's probe
> function. That is what I meant by matching but maybe I could had been more
> precise.

(So is what I2C currently does comparable to what, say, USB does (ie,
using usb_device_id for the match and also passing it to the driver's
probe function) or is it more complicated?)

> > But I'm guessing that parsing a device tree blob that contains
> > strings like
> >     compatible = "silergy,syr828"
> > 
> > would add strings like
> >     MODALIAS=of:N[...]T[...]Csilergy,syr828
>
> That would be the correct behavior and is what the RFC patch #27 does.
>  
> > to the related uevents. (Likewise for the two other aliases.) Doesn't
> > that happen here?
>
> No, that is exactly the problem.

Which also explains how these
   MODULE_DEVICE_TABLE(of, ...);

lines, which have no effect for the drivers at hand, added to my confusion.

> Take a look to i2c_device_uevent() [0],
> it just does:
> 
> add_uevent_var(env, "MODALIAS=%s%s", I2C_MODULE_PREFIX, client->name))
> 
> So if you have a i2c_device_id table but no 
> MODULE_DEVICE_TABLE(i2c,...),
> then module autoload won't work.

Thanks for taking the time to explain all this to me.


Paul Bolle
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