On Fri, Sep 28, 2018 at 4:00 PM Li Yang <leoyang.li@xxxxxxx> wrote: > > On Fri, Sep 28, 2018 at 3:07 PM Rob Herring <robh+dt@xxxxxxxxxx> wrote: > > > > On Thu, Sep 27, 2018 at 5:25 PM Li Yang <leoyang.li@xxxxxxx> wrote: > > > > > > Hi Rob and Grant, > > > > > > Various device tree specs are recommending to include all the > > > potential compatible strings in the device node, with the order from > > > most specific to most general. But it looks like Linux kernel doesn't > > > provide a way to bind the device to the most specific driver, however, > > > the first registered compatible driver will be bound. > > > > > > As more and more generic drivers are added to the Linux kernel, they > > > are competing with the more specific vendor drivers and causes problem > > > when both are built into the kernel. I'm wondering if there is a > > > generic solution (or in plan) to make the most specific driver bound > > > to the device. Or we have to disable the more general driver or > > > remove the more general compatible string from the device tree? > > > > It's been a known limitation for a long time. However, in practice it > > doesn't seem to be a common problem. Perhaps folks just remove the > > less specific compatible from their DT (though that's not ideal). For > > most modern bindings, there's so many other resources beyond > > compatible (clocks, resets, pinctrl, etc.) that there are few generic > > drivers that can work. > > > > I guess if we want to fix this, we'd need to have weighted matching in > > the driver core and unbind drivers when we get a better match. Though > > it could get messy if the better driver probe fails. Then we've got to > > rebind to the original driver. > > Probably we can populate the platform devices from device tree after > the device_init phase? So that all built-in drivers are already > registered when the devices are created and we can try find the best > match in one go? For more specific loadable modules we probably need > to unbind from the old driver and bind to the new one. But I agree > with you that it could be messy. > > > > > Do you have a specific case where you hit this? > > Maybe not a new issue but "snps,dw-pcie" is competing with various > "fsl,<chip>-pcie" compatibles. Also a specific PHY > "ethernet-phy-idAAAA.BBBB" with generic "ethernet-phy-ieee802.3-c45". The ethernet-phy issue is not related to the general device binding framework, it should be an issue with the of_mdio framework. But it is still a inalignment with the device tree recommendation. Regards, Leo
