linux-kernel - Re: [PATCH] parport: Add character LCD driver for da850/omap-l138

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Message-Id: <20090903152042.bec9e4b8.akpm@linux-foundation.org>
Date:	Thu, 3 Sep 2009 15:20:42 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Sudhakar Rajashekhara" <sudhakar.raj@...com>
Cc:	pavel@....cz, linux-parport@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	davinci-linux-open-source@...ux.davincidsp.com,
	Greg KH <greg@...ah.com>
Subject: Re: [PATCH] parport: Add character LCD driver for da850/omap-l138

On Wed, 2 Sep 2009 19:23:27 +0530
"Sudhakar Rajashekhara" <sudhakar.raj@...com> wrote:

> On Tue, Sep 01, 2009 at 18:53:30, Pavel Machek wrote:
> > Hi!
> > 
> > > On TI DA850/OMAP-L138 EVM, HD44780 (24x2) LCD panel is
> > > being used, interfaced through the SoC specific LCD
> > > interface[1].
> > > 
> > > Driver from drivers/staging/panel/panel.c works for this
> > > LCD panel but that driver expects the LCD panel to be
> > > interfaced through a parallel port.
> > > 
> > > This patch implements a dummy parallel port driver which
> > > interfaces to the panel driver in staging area through the
> > > LCD interface available on SoC.
> > 
> > This is a nasty hack, right? Just fixup panel.c to work with your
> > interface, too?
> > 								Pavel
> > 
> 
> Agree, that this is a hack. I have submitted a patch which modifies
> panel.c to support this kind of interface.
> 
> Currently the problem with panel.c is that, it is tightly coupled
> with parallel port interface. Panel driver needs to be completely
> re-written to de-couple parallel port related stuff. If I have to
> do this, then I need to start from ground zero as I do not have a
> setup on which HD44780 panel has been interfaced using parallel
> port. But I can certainly help here by testing such a modification
> to the panel driver by testing on the hardware what I have.
> 
> In the meantime, can I re-submit this patch by moving the dummy
> parallel port driver to reside in staging area? Later it can be
> moved/deleted depending on the modifications to the panel driver.
> 

If we're going to pull tricks like that then panel.c will never get
itself moved from outside staging/ :(

Really, I don't think we should be hacking things into drivers/parport/
code to accommodate design shortcomings in a staging/ driver.  Once done,
these things have a tendency to never be undone.
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