Messages in this thread | | | Date | Wed, 3 Jul 2013 10:54:04 +0200 | From | Christian Ruppert <> | Subject | Re: [PATCH v2] pinctrl: elaborate a bit on arrangements in doc |
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On Thu, Jun 27, 2013 at 04:00:49PM -0600, Stephen Warren wrote: > On 06/27/2013 03:54 AM, Linus Walleij wrote: > > From: Linus Walleij <linus.walleij@linaro.org> > [...] > > +From a kernel point of view, however, these are different aspects of the > > +hardware and shall be put into different subsystems. > > + > > +Electrical properties of the pin such as biasing and drive strength > > +may be placed at some pin-specific register in all cases or as part > > +of the GPIO register in case (B) especially. This doesn't mean that such > > +properties necessarily pertain to what the Linux kernel calls "GPIO". > > Is it worth explaining which Linux subsystem each of the three aspects > are controlled by. Something like: > > ----- > Registers (or fields within registers) that control electrical > properties of the pin such as biasing and drive strength should be > exposed through the pinctrl subsystem, as "pin configuration" settings. > > Registers (or fields within registers) that control muxing of signals > from various other HW blocks (e.g. I2C, MMC, or GPIO) onto pins should > be exposed through the pinctrl subssytem, as mux functions. > > Registers (or fields within registers) that control GPIO functionality > such as setting a GPIO's output value, reading a GPIO's input value, or > setting GPIO pin direction should be exposed through the GPIO subsystem. > > Depending on the exact HW register design, some functions exposed by the > GPIO subsystem may call into the pinctrl subsystem in order to > co-ordinate register settings across HW modules. In particular, this may > be needed for HW with separate GPIO and pin controller HW modules, where > e.g. GPIO direction is determined by a register in the pin controller HW > module rather than the GPIO HW module. > -----
I agree, this is really worth mentioning in some place, maybe even a more prominent one than here.
-- Christian Ruppert , <christian.ruppert@abilis.com> /| Tel: +41/(0)22 816 19-42 //| 3, Chemin du Pré-Fleuri _// | bilis Systems CH-1228 Plan-les-Ouates -- 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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