linux-kernel - Re: [PATCH 6/6 V4] input: STMPE touch controller support

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Message-ID: <20100624130108.GE26189@bnru02.bnr.st.com>
Date:	Thu, 24 Jun 2010 18:31:09 +0530
From:	Rabin VINCENT <rabin.vincent@...ricsson.com>
To:	Luotao Fu <l.fu@...gutronix.de>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	STEricsson_nomadik_linux <STEricsson_nomadik_linux@...t.st.com>
Subject: Re: [PATCH 6/6 V4] input: STMPE touch controller support

On Thu, Jun 24, 2010 at 14:42:10 +0200, Luotao Fu wrote:
> On Thu, Jun 24, 2010 at 06:01:53PM +0530, Rabin VINCENT wrote:
> > On Thu, Jun 24, 2010 at 13:13:41 +0200, Luotao Fu wrote:
> > > +       ret = stmpe_set_bits(stmpe, STMPE_REG_TSC_FRACTION_Z,
> > > +                       FRACTION_Z(ts->fraction_z),
> > > +                       FRACTION_Z(ts->fraction_z));
> > 
> > I think your earlier revisions had this same behaviour, but this only
> > writes the bits you are trying to set, and it may be a problem if there
> > are other bits already set in this field.  I don't know if this is a
> > concern with this block, but if it is, you can do something like the
> > following to clear out the field before writing:
> > 
> 
> This is done intentionally to leave the bits alone which I don't want.
> Most of the registers here are used exclusively for the touchscreen.
> Some others are shared with the ADC. The ADC however doesn't have any
> own configuration and has to go with the configuration of the touch
> screen. Hence it's OK, even probably better not to touch the bits we
> don't need.

I meant something like: let's say you want to change the "count of the
fractional part" (I quote from your platdata).  It (the FRACTION_Z
field, I assume) has a default value of (say) 2.  Say you want to change
the count to 1.  The above write will change it to 3 instead.  If this
is really the behaviour you need, it should be OK then.

Rabin
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