Hi Simon, On Thu, May 30, 2024 at 03:30:39PM -0600, Simon Glass wrote: > On Wed, 29 May 2024 at 11:02, Elliot Berman <quic_eber...@quicinc.com> wrote: > > On Wed, May 29, 2024 at 10:18:43AM -0600, Simon Glass wrote: > > > On Mon, 20 May 2024 at 18:27, Elliot Berman <quic_eber...@quicinc.com> > > > wrote: > > > > On Sun, May 19, 2024 at 12:22:47PM -0600, Simon Glass wrote: > > > > > I believe the compatible string is still the best approach. It has a > > > > > number of benefits: > > > > > > > > > > 1. It is in fact the purpose of compatible strings to match hardware > > > > > with a driver > > > > > > > > Agreed. Compatible string matching works great for the rest of the > > > > device tree, but I think matching the root node compatible has different > > > > challenges that the rest of DT doesn't have. > > > > > > > > I'm open to use compatible strings, but we (EBBR) should describe how > > > > OSes should pick the DTB based on the compatible strings given by > > > > firmware so that there is consistency. > > > > > > Yes, agreed. Do you have a proposal for this? > > > > > > > AMD did some work based off regex strings, maybe this could be expanded > > and made part of the EBBR and DT spec [1]. > > > > [1]: https://resources.linaro.org/en/resource/q7U3Rr7m3ZbZmXzYK7A9u3 > > OK, thanks. Note that I consider this a vendor-specific addition to > U-Boot, similar to the 'hat' approach used by Beaglebone. The actual > mechanism is using overlays, from what I can tell, with the DT > modified in Linux by applying overlays. Is that right? If so, it > doesn't seem relevant to what you propose here. > > I think you should take a look at how far you can get with just > compatible strings, so we can see what is actually missing. >
The talk and slides I gave at EOSS covered the challenges we had in implementing a typical compatible string-based mechanism for DT selection. [snip] > > > > The scenario I like to think about is where OS wants to run on many > > boards/platforms and wants to override DTB for only some of those > > boards/platforms. Perhaps the firmware-provided DTB on most of the > > boards is good for the OS, but not good enough for couple boards and the > > OS provides its own. Firmware has to provide enough information that OS > > can pick the DTB and also OS need to be able to detect that it doesn't > > have a DTB for the platform and should fallback to the firmware-provided > > DT. > > > > Maybe the scenario I think about isn't valid -- in that case, we should > > make sure that the spec says something about how "if OS wants to provide > > own DTB, it must have DTBs for all the boards the OS could run on". > > > > I don't know of an OS that can find its own DTB. Which particular OS > are you thinking of? Aren't most devices doing that today? Relatively few devices are using firmware-provided DTs. - Elliot _______________________________________________ boot-architecture mailing list -- boot-architecture@lists.linaro.org To unsubscribe send an email to boot-architecture-le...@lists.linaro.org
