On Tue, Apr 24, 2018 at 06:55:45PM +0100, Mark Rutland wrote: > Hi bartosz, > > On Tue, Apr 24, 2018 at 07:30:40PM +0200, Bartosz Golaszewski wrote: > > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> > > > > Device tree based systems often use OF_DECLARE() macros for devices > > that need to be initialized early in the boot process such as clocks, > > timers etc. However platform devices are more desirable. > > > > This series aims at introducing support for early platform drivers for > > OF-based systems. > > > > The idea is to have a special compatible fallback string: "earlydev" > > that similarily to "syscon" would be added to device nodes that need > > early probing. We then need to call of_early_platform_populate() early > > in the boot process to actually probe the registered devices. > > > > I am aware that this new compatible does not strictly correspond with > > the "hardware description only" rule of DT, but we already have many > > functionalities that break this rule: syscon, gpio hogs etc. > > I don't think we need the "earlydev" string at all, and can still keep > the rest of this infrastrcuture if it is helpful. > > So while I'm certainly oppposed to the "earlydev" string, I think that > the infrastrcuture could be useful. Yes. I think this agrees with my objection -- I'm not opposed to the infrastructure in the kernel, but to semantically-wrong and backwards-incompatible changes to the device tree contract. > > The first user of this new functionality will be the DaVinci platform > > for which we want to probe the pll, psc and timer drivers early in the > > boot sequence but keep them implemented as platform drivers. > > Can we have early_paltform_driver() take a reference to the driver's > of_match_table, and put that in a special section? > > Then instead of looking for "earlydev", we look for any compatible > string in that section. No magic string required in the DT, and we can > always mess around with probe ordering in future. Yes, this is pretty much exactly the change I had in mind. Rich -- 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
