On Thursday 13 September 2012 14:22:57 Tomi Valkeinen wrote: > * PGP Signed by an unknown key > > On Thu, 2012-09-13 at 15:08 +0900, Alex Courbot wrote: > > > On Thursday 13 September 2012 13:45:39 Tomi Valkeinen wrote: > > > > > > Old Signed by an unknown key > > > > > > > > > On Wed, 2012-09-12 at 18:57 +0900, Alexandre Courbot wrote: > > > > > > > > > > Some device drivers (panel backlights especially) need to follow > > > > precise > > > > sequences for powering on and off, involving gpios, regulators, PWMs > > > > with a precise powering order and delays to respect between each > > > > steps. > > > > These sequences are board-specific, and do not belong to a particular > > > > driver - therefore they have been performed by board-specific hook > > > > functions to far. > > > > > > > > > > > > The sequences are not board-specific, they are device (backlight, etc.) > > > specific. The sequences have been handled in board-specific hook > > > functions so far because there hasn't been proper drivers for the > > > devices. > > > > > > If I were to take the same panel (and backlight) you have and install > > > it > > > on my board, I would need the same power sequence. > > > > > > You could also have power sequences that control a set of GPIOs for an > > external interface (and would then be more board-specific), but you are > > right > > What do you mean with "external interface"? Any crazy circuit design that would make the regular power sequence not usable on a specific board. Sorry, I don't have any concrete example in mind, the above is just speculation. > But it's true that there can always be interesting board specific > hardware designs, and they truly are board specific. In my experience > these are quite rare, though, but perhaps not so rare that we wouldn't > need to care about them. > > However, I fear these board specific things may be quite a bit anything, > so it may well be pwm, gpios and regulators are not enough for them. For > example, there could be an FPGA on the board which requires some > configuration to accomplish the task at hand. It could be rather > difficult to handle it with a generic power sequence. Right. Note that this framework is supposed to be extended - I would like to at least add regulator voltage setting, and maybe even support for clocks and pinmux (but that might be out of place). > So I guess what I'm saying is that mostly these issues are device > specific, and when they are not, they may be rather complex/strange and > require c code. You're definitely right about the powering issue being a device issue 99% of the time. For the rest I do not have enough insight to emit an opinion. Alex. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
