On Mon, Aug 10, 2015 at 11:50:16AM +0200, Linus Walleij wrote: > On Tue, Aug 4, 2015 at 11:23 AM, Markus Pargmann <mpa@xxxxxxxxxxxxxx> wrote: > > > This patch adds a sysfs attribute 'name' to gpios that were exported. It > > exposes the newly added name property of gpio descriptors. > > > > Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> > > This needs to also patch Documentation/ABI/testing/sysfs-gpio > if we should go with it. It says this: Right, forgot about that documentation. > > /sys/class/gpio > /export ... asks the kernel to export a GPIO to userspace > /unexport ... to return a GPIO to the kernel > /gpioN ... for each exported GPIO #N > /value ... always readable, writes fail for input GPIOs > /direction ... r/w as: in, out (default low); write: high, low > /edge ... r/w as: none, falling, rising, both > > Anyways I don't know if this is right, and that ABI doc is also lying. > > Look at this in gpiolib-sysfs.c: > > if (chip->names && chip->names[offset]) > ioname = chip->names[offset]; > > dev = device_create_with_groups(&gpio_class, chip->dev, > MKDEV(0, 0), data, gpio_groups, > ioname ? ioname : "gpio%u", > desc_to_gpio(desc)); > > I.e. what the ABI doc say about the dirs being named "gpioN" is > a plain lie, it can have a descriptive name as its directory name > under /sys/class/gpio/foo-line or so. > > Since this already exist and is a flat namespace ... we should > use that. > > However it has the implication like I said before that two names > cannot be the same. I think Johan's comment that they could > be non-unique did not take into account the fact that two chips > could use the same .names array (and that would already fail, > by the way) so the .names in the struct gpio_chip *MUST* be > unique as compared to all other names. > > We *could* deprecate the old line naming mechanism (that create > dirs named after the pin), and from here on only use gpioN and > "name" in a separate file like this patch does. However that is > not really OK either: we want to move away from the GPIO numbers > and to descriptors and descriptive names, so I currently feel > we should name the directories after the line instead, and > require them to be unique. Ok, this also answers the question I just had in the other mail. Best Regards, Markus > > I'll have to patch this document now anyways because it is > lying about the ABI :( > > Yours, > Linus Walleij > -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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