On Mon, Jun 18, 2018 at 3:22 PM, Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On 18 June 2018 at 14:21, Arnd Bergmann arnd@arndb.de wrote:
On Mon, Jun 18, 2018 at 9:45 AM, Linus Walleij linus.walleij@linaro.org wrote:
Also, given that we can (and do) already describe topologies involving mezzanines by ignoring the connector altogether (which is not entirely unreasonable given the fact that we [as Linaro/96boards] dropped the ball on this one and did not mandate discoverability for mezzanines). So ideally, DTs can be expressed such that older kernels can still use those peripherals.
Not sure. Modeling the connector as a device with its own driver does seem like a significant advantage, which to me weighs more than backward compatibility with old kernels. We can clearly always describe the devices behind the connector individually and ignore the connector on old kernels and we should still allow running DT files that work with the old kernels on new kernels, but I don't see running new DT files on old kernels as essential in this case. Many platforms don't actually care about that case at all today (but some do of course).
Arnd