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. - Felix
