Messages in this thread | | | Date | Fri, 18 Feb 2011 19:49:54 +0100 | From | Uwe Kleine-König <> | Subject | Re: [PATCH v3 2/4] gpiolib: Add ability to get GPIO pin direction |
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Hello Peter,
On Fri, Feb 18, 2011 at 11:36:26AM -0600, Peter Tyser wrote: > On Fri, 2011-02-18 at 09:57 +0100, Uwe Kleine-König wrote: > > On Thu, Feb 17, 2011 at 05:03:17PM -0600, Peter Tyser wrote: > > > Add a new get_direction() function to the gpio_chip structure. This is > > > useful so that the direction of a pin can be determined when its > > > initially exported. Previously, the direction defaulted to "unknown" > > > regardless of the actual configuration of the GPIO pin. > > > > > > If a GPIO driver implements get_direction(), it is called in > > > gpio_request() to set the initial direction of the pin accurately. > > IMHO the commit log is conceptually wrong, because it talks about a > > "pin". Better use gpio here. > > I don't follow. I used "pin" to make it clear that the get_direction() > function operates on a pin-by-pin basis, and to help reduce any > ambiguity about if a gpio chip or gpio pin is being referred to. Would > you prefer that the "pin" references are clarified to be "GPIO pin"? Maybe it's just that we use different terms. For me a "pin" is an entry/exit point into/from a cpu or other chip. A gpio is (hmm, how should I say) a concept how to drive a pin. A gpio might or might not be "connected" to a pin at a given time.
> > > Cc: Alek Du <alek.du@intel.com> > > > Cc: Samuel Ortiz <sameo@linux.intel.com> > > > Cc: David Brownell <dbrownell@users.sourceforge.net> > > > Cc: Eric Miao <eric.y.miao@gmail.com> > > > Cc: Uwe Kleine-K?nig <u.kleine-koenig@pengutronix.de> > > > Cc: Mark Brown <broonie@opensource.wolfsonmicro.com> > > > Cc: Joe Perches <joe@perches.com> > > > Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> > > > Cc: Grant Likely <grant.likely@secretlab.ca> > > > Signed-off-by: Peter Tyser <ptyser@xes-inc.com> > > > --- > > > Changes since v1: > > > - Add support for "unknown" direction > > > > > > Changes since v2: > > > Based on Wolfram's feedback: > > > - Use GPIOF_DIR_* flags as returns from get_direction() > > > - Call spin_lock_irqsave() to before setting flags > > > > > > drivers/gpio/gpiolib.c | 23 +++++++++++++++++++++++ > > > include/asm-generic/gpio.h | 4 ++++ > > > 2 files changed, 27 insertions(+), 0 deletions(-) > > > > > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > > > index eb74311..a656a2c 100644 > > > --- a/drivers/gpio/gpiolib.c > > > +++ b/drivers/gpio/gpiolib.c > > > @@ -1174,6 +1174,7 @@ int gpio_request(unsigned gpio, const char *label) > > > struct gpio_desc *desc; > > > struct gpio_chip *chip; > > > int status = -EINVAL; > > > + int dir; > > > unsigned long flags; > > > > > > spin_lock_irqsave(&gpio_lock, flags); > > > @@ -1214,6 +1215,28 @@ int gpio_request(unsigned gpio, const char *label) > > > } > > > } > > > > > > + if (chip->get_direction) { > > > + /* chip->get_direction may sleep */ > > > + spin_unlock_irqrestore(&gpio_lock, flags); > > might_sleep_if(chip->can_sleep) ? > > Makes sense. I was following the lead of chip->request() in the same > function, which doesn't use might_sleep_if(). I assume might_sleep_if() > should be added to it as well in a separate patch? I was there first :-) http://mid.gmane.org/1297977533-17794-1-git-send-email-u.kleine-koenig@pengutronix.de
> > > + dir = chip->get_direction(chip, gpio - chip->base); > > > + spin_lock_irqsave(&gpio_lock, flags); > > > + switch (dir) { > > > + case GPIOF_DIR_OUT: > > > + set_bit(FLAG_DIR_OUT, &desc->flags); > > > + clear_bit(FLAG_DIR_IN, &desc->flags); > > > + break; > > > + case GPIOF_DIR_IN: > > > + set_bit(FLAG_DIR_IN, &desc->flags); > > > + clear_bit(FLAG_DIR_OUT, &desc->flags); > > > + break; > > > + default: > > > + /* Direction isn't known */ > > > + clear_bit(FLAG_DIR_OUT, &desc->flags); > > > + clear_bit(FLAG_DIR_IN, &desc->flags); > > > + break; > > > + } > > Alternatively to my suggestion for patch1: > > } else { > > clear_bit(FLAG_DIR_OUT, &desc->flags); > > clear_bit(FLAG_DIR_IN, &desc->flags); > > I like this way better too. I'll initialize dir = -1 and pull the > switch statement out of the conditional, like: > > if (chip->get_direction) { > /* chip->get_direction may sleep */ > spin_unlock_irqrestore(&gpio_lock, flags); > might_sleep_if(chip->can_sleep); > dir = chip->get_direction(chip, gpio - chip->base); > spin_lock_irqsave(&gpio_lock, flags); > } > > switch (dir) { > case GPIOF_DIR_OUT: > set_bit(FLAG_DIR_OUT, &desc->flags); > clear_bit(FLAG_DIR_IN, &desc->flags); > break; > case GPIOF_DIR_IN: > set_bit(FLAG_DIR_IN, &desc->flags); > clear_bit(FLAG_DIR_OUT, &desc->flags); > break; > default: > /* Direction isn't known */ > clear_bit(FLAG_DIR_OUT, &desc->flags); > clear_bit(FLAG_DIR_IN, &desc->flags); > break; > } fine
Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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