Hi Stephen, On Tue, Jan 24, 2012 at 3:14 PM, Stephen Warren <swar...@nvidia.com> wrote: > Simon Glass wrote at Tuesday, January 24, 2012 4:12 PM: >> On Mon, Jan 23, 2012 at 10:18 AM, Stephen Warren <swar...@nvidia.com> wrote: >> > On 01/21/2012 10:08 AM, Simon Glass wrote: >> >> Hi Stephen, >> >> >> >> On Wed, Jan 18, 2012 at 2:17 PM, Stephen Warren <swar...@nvidia.com> >> >> wrote: >> >>> On 01/11/2012 09:32 PM, Simon Glass wrote: >> >>>> This adds some support into fdtdec for reading GPIO definitions from >> >>>> the fdt. ... >> > ... >> >>>> diff --git a/include/fdtdec.h b/include/fdtdec.h >> >>> ... >> >>>> +/* GPIOs are numbered from 0 */ >> >>>> +enum { >> >>>> + FDT_GPIO_NONE = -1U, /* an invalid GPIO used to end our list */ >> >>> >> >>> Is this due to the way U-Boot works right now, or something defined by >> >>> this patch? It's been pointed out that the kernel's choice to use -1 as >> >>> "invalid GPIO" rather than 0 was a mistake, since that prevents GPIO >> >>> fields being easily added to platform data structures, since you then >> >>> have to go and initialize every new instance to -1, rather than relying >> >>> on BSS initializing it to 0. I assume this is just the way U-Boot works, >> >>> so solving this is outside the scope of this patch. >> >> >> >> It is nothing to do with U-Boot itself - we can choose any number. >> > >> > Surely the value you choose for DT parsing has to align with the value >> > that U-Boot's GPIO API chooses, so you can't just choose any number. >> >> No, in the fdt we just leave out the gpio if it is not required. The >> FDT_GPIO_NONE is purely internal to U-Boot. > > That's consistent with what I said; I'm talking about the value that a > missing DT property translates into within U-Boot.
OK I see. I'm not proposing to change U-Boot convention now (if in fact it has one). At least FDT_GPIO_NONE is a constant that people need to check against (but they should use fdt_gpio_isvalid() instead). We can adjust this in the future if U-Boot people want to. Regards, Simon > > -- > nvpublic > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot