H Hartley Sweeten wrote: > > FWIW, the gpiolib API will accept any non-zero value to "set" a gpio pin > and a zero value to "clear" the pin. > It makes me sort of cringe to say this, but I'm going to assume that the API is intended to work that way so that I can take advantage of it. But I'd love to someday have the reassurance that gpiolib really *is* intended to work that way (might be a bad idea though, see below). Call me paranoid, but I've lost a lot of hair over the years undoing the damage of similar failed assumptions. I've found the Linux kernel code to be refreshingly forgiving of such things, however, so I'm willing to risk it this time. :) > For that matter, some of the gpiolib drivers end up returning the bit > position mask for a given gpio pin and not 1 or 0. For instance if the > gpio pin in question is bit 6 in an 8-bit register and it is set, a > __gpio_get_value will end up returning 0x40 and not '1'. > Who's to say that gpios should always be boolean? On the output side, a "gpio" that's four bits wide might be a useful way of dealing with bar graphs, seven-segment displays, etc. (but more specialized abstractions might be more appropriate, of course). A two-bit "gpio" input might make it easier to deal with rotary encoders. But for now, GPIOs are assumed to be booleans and that's why I'm hesitant to feed the API non-boolean values. Someday, those values might mean something subtly but disastrously different. And given my luck lately with such things... b.g. -- Bill Gatliff Embedded systems training and consulting http://billgatliff.com bgat@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
