On Mon, Nov 23, 2009 at 8:29 AM, Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Nov 20, 2009 at 03:21:31PM -0700, Grant Likely wrote: >> On Tue, Nov 17, 2009 at 1:27 AM, David Brownell <david-b@xxxxxxxxxxx> wrote: > >> > Since *everything* boils down to one or more signal lines, >> > your argument leads directly to Linux having no native >> > hardware interface except GPIOs. ?Not ... practical. ;) > >> I think you've missed my point and taken it to an illogical extreme to >> counter it. I agree that PWMs are not GPIOs and visa versa. However, >> *some* devices are both GPIOs and PWMs. Also what is needed to manage >> GPIO and PWM pins is pretty much identical. > > On most of the ARM SoCs PWM and GPIO aren't particularly special here - > most of the on-SoC functionality is multiplexed onto pins through the > same hardware interface. A very large proportion of the pins of the SoC > will have muxes to bring out the signals from the internal IP blocks, > and pretty much all of those will have GPIO as one of those functions. Right, pin-mux is a different problem. But there are also devices that implement both PWM and GPIO functionality in the same IP block. I think pin muxing, and pin controller drivers are different problem domains and should be handled separately. >> But that *isn't* the primary purpose of the GPIO subsystem. All that >> stuff is layered on top of the GPIO pin management code and doesn't >> really play into this debate. > > The GPIO subsystem isn't doing pin management in that way for most > systems, it's just controlling the GPIO functionality and relies on > separate configuration to ensure that the relevant pins are in GPIO > mode. Sorry. when I said pin management I meant how Linux keeps track of pin controllers. Not pin mux. I should use different terminology perhaps to reduce confusion. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. -- 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
