On Fri, Jul 26, 2019 at 12:43 AM Rob Herring <robh@xxxxxxxxxx> wrote: > On Thu, Jul 25, 2019 at 12:23 AM H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> wrote: > > I tried to convince Linus that this is the right way but he convinced > > me that a fix that handles all cases does not exist. > > > > There seem to be embedded devices with older DTB (potentially in ROM) > > which provide a plain 0 value for a gpios definition. And either with > > or without spi-cs-high. > > > > Since "0" is the same as "GPIO_ACTIVE_HIGH", the absence of > > spi-cs-high was and must be interpreted as active low for these > > devices. This leads to the inversion logic in code. > > > > AFAIR it boils down to the question if gpiolib and the bindings > > should still support such legacy devices with out-of tree DTB, > > but force in-tree DTS to add the legacy spi-cs-high property. > > > > Or if we should fix the 2 or 3 cases of in-tree legacy cases > > and potentially break out-of tree DTBs. > > If it is small number of platforms, then the kernel could handle those > cases explicitly as needed. > > > IMHO it is more general to keep the out-of-tree DTBs working > > and "fix" what we can control (in-tree DTS). > > If we do this, then we need to not call spi-cs-high legacy because > we're stuck with it forever. I agree. The background on it is here: https://lkml.org/lkml/2019/4/2/4 Not using the negatively defined (i.e. if it is no there, the line is by default active low) spi-cs-high would break PowerPC, who were AFAICT using this to ship devices. Yours, Linus Walleij
