On Thu, Oct 18, 2012 at 6:38 AM, Daniel Glöckner <daniel...@gmx.net> wrote: > On Mon, Oct 15, 2012 at 10:30:15PM +0200, Linus Walleij wrote: >> >> Another patch that is circulating concerns edge triggers and similar, >> and it appear that some parts of the GPIO sysfs is for example >> redefining and exporting IRQchip properties like trigger edge >> in sysfs, while the settings of the irqchip actually used by the driver >> is not reflected in the other direction. So you can *set* these things >> by writing in the GPIO sysfs, but never trust what you *read* from >> there. And you can set what edges an IRQ will trigger on a certain >> GPIO, and the way to handle the IRQs from usespace is to poll >> on a value. This is not really documented but well ... > > Part of this sounds like you are not familiar with the GPIOlib sysfs > IRQ stuff.
Yeah you bet :-) I'm just trying to maintain it, I think I need your help with this. Do you think it'd be possible for you to augment the Documentation/gpio.txt file with some userspace code examples? I think this could be very useful. > The trigger edge set in sysfs is only used when userspace > polls the GPIO via sysfs. Drivers that want to register a gpio IRQ > should IMHO always explicitly request the edge/level to trigger on and > they should request the gpio beforehand. This prevents the gpio from > being exported to userspace. Only IRQ triggers accepted by the irq chip > are settable in sysfs, so you can trust the value read from that file. OK. >> Daniel: are you interested in helping us fixing the GPIOlib >> sysfs ABI and kernel internals? I'm a bit afraid of it. > > Actually I don't know what you want to change to fix the existing sysfs > ABI. Personally I'd like to see the following things changed: > - /sys/gpio/.../direction does not correspond to hardware before first > use of gpio_direction_* due to lack of gpio_get_direction. > - Names given to gpios by the chip should just result in symlinks to > the usual gpioX directories or (un)exporting of gpios should accept > names. Please send a patch! I'll merge. Actually I'm mostly referring to another floating patch, I will try to dig it up and CC you. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
