Messages in this thread |  | | | Date | Wed, 7 Dec 2011 00:02:03 +0100 | | Subject | Re: [PATCH 1/2 v5] pinctrl: add a pin config interface | | From | Linus Walleij <> |
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Hm, at some point I hit the wrong reply button so the list missed mine and Stephens replies :-/ sorry. Quoting verbose.
On Mon, Dec 5, 2011 at 6:56 PM, Stephen Warren <swarren@nvidia.com> wrote: > Linus Walleij wrote at Monday, December 05, 2011 8:43 AM: >> On Thu, Dec 1, 2011 at 10:44 PM, Stephen Warren <swarren@nvidia.com> wrote: >> > Linus Walleij wrote at Thursday, December 01, 2011 3:55 AM: > ... >> >> +extern int pin_config_get(struct pinctrl_dev *pctldev, int pin, >> >> + unsigned long *config); >> >> +extern int pin_config_set(struct pinctrl_dev *pctldev, int pin, >> >> + unsigned long config); >> > >> > Should the per-pin APIs take a pin name (char*) instead of a pin number >> > just like the per-group APIs? That seems more consistent. Currently, only >> > the pinctrl core -> driver API ever deals with pin numbers, and e.g. the >> > mapping table only deals with names. >> >> But the group definitions deal only with numbers. >> >> And the name is not compulsory, and not required to be >> unique. Which is in turn a side effect of the fact that some chip >> engineers insist on doing crazy stuff like naming 15 different >> pins "GND". So requireing them to all be uniquely named >> could lead to enforcing som arbitrary naming policy which >> cause a disalignment with terms found in the data sheet, >> or just bring us full circle back to pin numbers by prefixing >> or suffixing each name with a number albeit in ASCII... >> >> So we'd better stick with numbers ftm, as pointed out >> we want to get rid of casual use of these functions >> anyway. > > The big problem here is: How do users of these APIs know what the pin > numbers are? With names, the datasheet presumably gives standard names > to each pin, whereas the numbering scheme chosen by a pinctrl driver can > be essentially arbitrary (well, perhaps not with a PLCC package, but > with others...). I suppose the driver could expose a header with all the > names in, but it seems like we're trying to get away from that kind of > thing. > > Related, numbers in device tree suck, since there's currently no way of > using symbolic constants. I suppose the DT parsing code would do a mapping > from text name to pin number using the driver's exposed table of pins > though. > > Re: unique names: Every pins does have a unique name. "GND" is really > the semantics of the pin, not its name; it always has some defined ball, > pad, or pin number which can be included in the name to make it unique. > I'd certainly vote for making pin names mandatory and unique.
Hm, you are making a perfectly good point about cross-referencing documentation. And matches my experience.
I certainly have to look into this.
So I need to make pin names - compulsory - unique - reqrite API accessors
I think it can be done since the in-tree drivers have all unique pin names.
I'll hack on this, it'll be a good step forward.
Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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