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From: David Brownell <david-b@pacbell.net>
To: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch 2.6.28-rc4] gpiolib: extend gpio label column width in debugfs file
Date: Thu, 13 Nov 2008 17:13:38 -0800
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Cc: Jarkko Nikula <jarkko.nikula@nokia.com>, linux-kernel@vger.kernel.org,
       stable@kernel.org
References: <1226472973-16271-1-git-send-email-jarkko.nikula@nokia.com> <20081113170211.23bf0343.akpm@linux-foundation.org>
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On Thursday 13 November 2008, Andrew Morton wrote:
> On Wed, 12 Nov 2008 08:56:13 +0200
> Jarkko Nikula <jarkko.nikula@nokia.com> wrote:
> 
> > There are already various drivers having bigger label than 12 bytes. Most
> > of them fit well under 20 bytes but make column width exact so that
> > oversized labels don't mess up output alignment.
> 
> Please provide before-and-after example output for this sort of change
> so that we can better understand its effect.
> 
> > Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.com>

I meant to send:

Acked-by: David Brownell <dbrownell@users.sourceforge.net>

... thanks Jarkko.


> > ---
> >  drivers/gpio/gpiolib.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index faa1cc6..82020ab 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -1134,7 +1134,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
> >  			continue;
> >  
> >  		is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
> > -		seq_printf(s, " gpio-%-3d (%-12s) %s %s",
> > +		seq_printf(s, " gpio-%-3d (%-20.20s) %s %s",
> >  			gpio, gdesc->label,
> >  			is_out ? "out" : "in ",
> >  			chip->get
> 
> This is a non-backward-compatible change to a userspace interface.  It
> looks like a pretty safe one, but this is always a fairly big deal.

Not really; this is for debugfs, and formats for debug data
are not ABI-suitable.  Developers need the flexibility to
change that stuff ... for example, they can *already* override
the default format to show pullups/pulldowns, drive strength,
polarity inversion, debouncing, and other hardware-specific goodies.
 

> If we're going to make this change then we should backport it to
> 2.6.27.x, 2.6.26.x and to 2.6.25.x to minimise the chance that someone
> will write a parser which works on one kernel version and fails on
> another.
> 
> David?  Thoughts?

This is explicitly not supported for ABI-ish purposes.

If they aren't even using those parenthesis to delimit things, I'd
really need to question what happened to their grey cells!

- Dave


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