On Thu, Dec 10, 2015 at 6:52 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Wednesday 09 December 2015 17:19:52 John Stultz wrote: >> >> If the concern is that since DT is basically ABI, one might not want >> to have such a wide interface that specifies all the different >> reasons, I can understand that. Though I'm really not sure how else we >> would be able to specify the device supported the reboot reason logic >> w/o having something in the DT (since some device may use the same soc >> w/ the same reboot logic may use a different bootloader which doesn't >> support the reason methods). At that point if we don't describe the >> method clearly, it ends up being something closer to just a quirks >> list which we'd have to map internally to behavior, which doesn't seem >> great. >> >> Should we run into hardware that the proposed driver doesn't handle, >> we can introduce a new driver for those specific semantics, but this >> way we can share at least most of the logic, no? > > I think we need a layered approach, with some high-level code to > store the boot reason, but then support firmware specific backends > to that. If we just need a phandle for an SRAM partition and an offset > within it, that can be done by the high-level driver, but not > any of the more sophisticated communication methods. Hrm. This feels to me like over-design, though. We already have the restart notifiers to hook into, which provide the command string. So its just a matter of parsing the string and writing the appropriate magic in the appropriate way (to memory, registers, efi, whatever). The amount of code we'd be dealing with to have a front end and 3-4 back-ends, vs having 3-4 separate drivers seems like it would almost be the same. So why try to make a more complicated infrastructure? Simply renaming this driver to reboot_reason_sram.c or something makes it easy to add reboot_reason_efi.c later. The other part is, while there are many bits of hardware that have done varied things in the past, I'm not sure how hard we should try to design a super-infrastructure to support all these different solutions if no one is pushing them upstream. I'd rather design for what people are working to merge (admittedly, that's a bit selfish of a statement here ;), and then hope future hardware chooses to use the same mechanism, or adapt the infrastructure as folks try to merge new approaches. thanks -john -- 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
