linux-kernel - RE: [PATCH V3 1/2] tps6507x-ts: Add DT support

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Date:	Wed, 12 Jun 2013 06:53:21 +0000
From:	"Vishwanathrao Badarkhe, Manish" <manishv.b@...com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"rob@...dley.net" <rob@...dley.net>
Subject: RE: [PATCH V3 1/2] tps6507x-ts: Add DT support

Hi Dmitry,

On Mon, Jun 10, 2013 at 23:33:11, Dmitry Torokhov wrote:
> Manish,
> 
> On Mon, Jun 10, 2013 at 10:23:16AM +0000, Vishwanathrao Badarkhe, Manish wrote:
> > Hi Dmitry,
> > 
> > On Mon, Jun 10, 2013 at 11:34:42, Dmitry Torokhov wrote:
> > > Hi Manish,
> > > 
> > > On Tue, May 21, 2013 at 02:24:17PM +0530, Vishwanathrao Badarkhe, Manish wrote:
> > > 
> > > > +	struct touchscreen_init_data *init_data = NULL;
> > > > +	int err;
> > > > +
> > > > +	if (node)
> > > > +		node = of_find_node_by_name(node, "tsc");
> > > 
> > > Why do you have to locate OF node manually instead of already having it attached to the device stucture?
> > 
> > As TPS6507x is mfd device containing two nodes, regulator and touchscreen.
> > It is necessary to use "of_find_node_by_name" to find child "tsc" node 
> > of TPS6507x MFD device.
> 
> I understand that TPS6507x is a MFD device, However, I still do not understand why you do not attach OF data to the child platform device representing touch screen when you create it.

I gone through most of MFD devices in mainline kernel where "of_find_node_by_name" 
function is used in order to populate child node properties. 
See below example of max8925 MFD device. 

Max8025 MFD device has following modules
1. Touch screen
2. Charger
3. Backlight
4. regulator

In DT case, device node for max8925 MFD device is in "arch/arm/boot/dts/mmp2-brownstone.dts" 
file having child nodes as regulator, backlight and charger.
Respective drivers (regulator, backlight and charger) of max8925 MFD device used 
"of_find_node_by_name" function in order to populate child node properties.

Here, also same case for TPS6507x MFD device

TPS6507x MFD device has two childs:
1. regulator
2. touch screen.

Regulator driver for TPS6507x is already in mainline and using function 
"of_find_node_by_name" to populate device tree properties for regulators.
On similar lines I used "of_find_node_by_name" to populate device
tree properties for touch screen.

Still, I agreed that it is possible to attach OF data to child platform device
but it requires changes in MFD driver of TPS6507x.

Please let me know your opinion about this.

Thanks, 
Manish
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