On 2016-10-05 22:31, Rob Herring wrote: > On Wed, Oct 5, 2016 at 1:36 PM, Felix Fietkau <nbd@xxxxxxxx> wrote: >> On 2016-10-05 20:25, Martin Blumenstingl wrote: >>> On Mon, Oct 3, 2016 at 5:22 PM, Rob Herring <robh+dt@xxxxxxxxxx> wrote: >>>> On Sun, Oct 2, 2016 at 5:50 PM, Martin Blumenstingl >>>> <martin.blumenstingl@xxxxxxxxxxxxxx> wrote: >>>>> There are at least two drivers (ath9k and mt76) out there, where >>>>> devicetree authors need to override the enabled bands. >>>>> >>>>> For ath9k there is only one use-case: disabling a band which has been >>>>> incorrectly enabled by the vendor in the EEPROM (enabling a band is not >>>>> possible because the calibration data would be missing in the EEPROM). >>>>> The mt76 driver (currently pending for review) however allows enabling >>>>> and disabling the 2.4GHz and 5GHz band, see [0]. >>>>> >>>>> Based on the discussion of (earlier versions of) my ath9k devicetree >>>>> patch it was suggested [1] that we use enable- and disable- properties. >>>>> The current patch implements: >>>>> - bands can be enabled or disabled with the corresponding property >>>>> - if both (disable and enable) properties are given and a driver asks >>>>> whether the band is enabled then the logic will return false (= not >>>>> enabled, preferring the disabled flag) >>>>> - if both (disable and enable) properties are given and a driver asks >>>>> whether the band is disabled then the logic will return true (again, >>>>> preferring the disabled flag over the enabled flag) >>>>> >>>>> We can still change the logic to do what the mt76 driver does (I am >>>>> fine with both solutions): >>>>> - property not available: driver decides which bands to enable >>>>> - property set to 0: disable the band >>>>> - property set to 1: enable the band >>>> >>>> I prefer this way. Really, I'd prefer just a boolean disable property. >>>> I'm not sure why you need the enable. We usually have these tri-state >>>> properties when you want not present to mean use the bootloader or >>>> default setting. Try to make not present the most common case. >>> Felix: could you please give a few details why mt76 can not only >>> disable but also enable a specific band? >>> There is no specific comment in the sources [0] why this is needed. >>> All other drivers that I am aware of (ath9k, rt2x00) only allow >>> disabling a specific band, they never enable it (this has to be done >>> explicitly by the EEPROM). >> None of the devices use it at the moment, I probably added it when I >> played with a device that had broken EEPROM data. I guess I decided to >> do it this way because on many devices the band capability field simply >> cannot be trusted. >> I guess I would be okay with just having a disable property and adding >> an enable property later only if we end up actually needing it. > > If EEPROM is commonly wrong or missing, then seems like you want to > plan ahead and support both enable and disable. > > The other approach I've mentioned before is just put raw EEPROM data > into DT to override the EEPROM. This would be better if there's a > large number of settings you need. So far, other EEPROM settings didn't need to be changed. - Felix -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
