On 10/14/2013 11:51 PM, Terje Bergström wrote: > On 14.10.2013 21:14, Stephen Warren wrote: >> On 10/14/2013 08:00 AM, Thierry Reding wrote: >>> Yes, as long as the device tree files includes the most specific >>> value in the compatible this should still be possible. So we'd have >>> this: >>> >>> gr2d@54140000 { compatible = "nvida,tegra114-gr2d", >>> "nvidia,tegra20-gr2d"; ... }; >>> >>> and the driver will match on "nvidia,tegra20-gr2d" if the more >>> specific "nvidia,tegra114-gr2d" is not there. When the driver is >>> updated to support Tegra114 specific functionality, then a more >>> specific entry can be added to the compatible table to handle it. >> >> True, but the DT fragment above is also only accurate /if/ a driver >> that only knows about "nvidia,tegra20-gr2d" can operate 100% of the >> features in Tegra20 HW on Tegra114 HW forever. > > I don't know of any hardware incompatibility. The only difference is > related to something not directly to 2D. We moved host1x away from the > power domain, so in Tegra114 we're able to power gate 2D and EPP. The > DVFS tables are also different. > > I'd say say adding the compatible property "nvidia,tegra20-gr2d" for > Tegra114's 2D is accurate and we're able to use the match table to drive > any SW policy differences. The compatible value shouldn't be used for SW policy differences. DT is about HW, not SW policy. You have to decide: either the HW is 100% backwards-compatible, or it's not. You can't decide that the HW is compatible, but then require different compatible values. -- 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