linux-kernel - Re: [PATCH] add missing intialisation of bgc->dir

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Message-ID: <19985.59397.631201.89451@ipc1.ka-ro>
Date:	Mon, 4 Jul 2011 18:19:17 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] add missing intialisation of bgc->dir

Hi,

Grant Likely writes:
> On Mon, Jul 4, 2011 at 9:51 AM, Lothar Waßmann <LW@...o-electronics.de> wrote:
> > Hi,
> >
> >> > > I don't know if this is a valid thing to do or not.  Not every GPIO
> >> > > controller supports reading back the initial state from the direction
> >> > > register.  I suspect it is better to leave initialization of the
> >> > > direction to the gpio controller driver itself.
> >> > >
> >> > That would mean, that external software would have to have access to
> >> > the bgpio internal data structures which is a Bad Thing(TM) IMO. Or we
> >> > need a function that allows to explicitly initialize the internal
> >> > shadow registers.
> >>
> >> What device are you using this for.  Are you using the basic gpio
> >> platform_driver, or do you have a driver using the library part of the
> >> basic gpio code?
> >>
> > I'm using it via drivers/gpio/gpio-mxc.
> 
> You can safely do the "bgc->dir = bgc->read_reg(bgc->reg_dir);" in
> gpio-mxc after bgpio_init returns.
> 
I know I can do that, but IMO it's a horrible way of programming, to
let a higher SW layer freely mess with the data structures of another
SW layer. There should be accessor functions to do that!


Lothar Waßmann
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