Messages in this thread |  | | 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 |
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On Tue, 5 Feb 2013 11:33:02 +0100, Andreas Larsson <andreas@gaisler.com> 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 <andreas@gaisler.com> > --- > 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.
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