From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: [PATCH 1/2] gpio: gpio-generic: Fix bug in big endian bit conversion Date: Sat, 09 Feb 2013 14:58:55 +0000 Message-ID: <20130209145855.D517E3E328E@localhost> References: <1360060383-16880-1-git-send-email-andreas@gaisler.com> <1360060383-16880-2-git-send-email-andreas@gaisler.com> Return-path: In-Reply-To: <1360060383-16880-2-git-send-email-andreas@gaisler.com> Sender: linux-kernel-owner@vger.kernel.org To: Andreas Larsson , Linus Walleij Cc: Rob Herring , linux-kernel@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, software@gaisler.com List-Id: devicetree@vger.kernel.org On Tue, 5 Feb 2013 11:33:02 +0100, Andreas Larsson wrote: > The swap to convert LE to BE in bgpio_pin2mask_be should be on byte level, not > on bit level. > > Signed-off-by: Andreas Larsson > --- > drivers/gpio/gpio-generic.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/drivers/gpio/gpio-generic.c b/drivers/gpio/gpio-generic.c > index 05fcc0f..7f11537 100644 > --- a/drivers/gpio/gpio-generic.c > +++ b/drivers/gpio/gpio-generic.c > @@ -112,7 +112,10 @@ static unsigned long bgpio_pin2mask(struct bgpio_chip *bgc, unsigned int pin) > static unsigned long bgpio_pin2mask_be(struct bgpio_chip *bgc, > unsigned int pin) > { > - return 1 << (bgc->bits - 1 - pin); > + unsigned int bit = pin & 0x7; /* Bit number within byte */ > + unsigned int base = pin - bit; /* Pin that is bit 0 within byte */ > + > + return 1 << ((bgc->bits - base - 8) + bit); /* shifted base + bit */ Ah, sorry for my previous reply. I see you have seen gpio-generic. :-) No, the original calculation is correct. BE and LE bit numbering are opposite, bit Linux always uses LE numbers as far as bit masks are concerned. Therefore pin 0 is the most significant bit, and pin (nr_bits-1) is the least significant bit. g.