On 30-07-15, 20:53, Rafael J. Wysocki wrote: > Well, on ACPI systems we actually do probe CPU devices. We have a processor > driver there that binds to CPU devices and the cpufreq driver is just a > frontend to that.
Hmm, maybe I need to look at that in detail.. > So question is what prevents DT-based systems from doing it analogously. Don't have an answer to it yet. > Now, even if you use a fake platform device for that (I'm sure there are > reasons for doing that, but I'd very much like them to be explained), The other reason apart from the EPROBE_DEFER thing was to identify the right driver for a platform. For multiplatform kernels, there can be multiple cpufreq drivers present in the kernel and there was no other way to identify the right driver platform wants to probe. > then > all of the information on dependencies should already be available to the > ->probe callback of that device's driver, so it can check them before > registering the cpufreq interface, can't it? That's what we try to do today for cpufreq-dt, for example. But that has to be done for every possible policy the system can have as all might have separate resources to allocate. For cpufreq-dt, we do it only for cpu0 today, and assume others will work as well if cpu0 can. The real deal is that we need a probe() per policy here, for which init() fitted well :) > Essentially, what you're suggesting to do is something like: Make the ->probe > of one device's driver register a subsys interface for a specific bus type > and check what ->add_dev of that interface returns for each device on that > bus and if that is -EPROBE_DEFER, return it as its own return value. Do you > honestly think this is a good design? No. I don't really thing so. That's why I was asking for suggestions to do it proper. Maybe processor driver is the way to look for, I will investigate further on that. But until the time that is done, and I expect that to take some time, can't we check the return value of ->add_dev()? -- viresh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
