On 07/02/2024 12:42, Peter Griffin wrote: >>>>> #include <linux/soc/samsung/exynos-regs-pmu.h> >>>>> #include <linux/soc/samsung/exynos-pmu.h> >>>>> >>>>> #include "exynos-pmu.h" >>>>> >>>>> +static struct platform_driver exynos_pmu_driver; >>>> >>>> I don't understand why do you need it. You can have only one >>>> pmu_context. The moment you probe second one, previous becomes invalid. >>>> >>>> I guess you want to parse phandle and check if just in case if it points >>>> to the right device, but still the original code is not ready for two >>>> PMU devices. I say either this problem should be solved entirely, >>>> allowing two devices, or just compare device node from phandle with >>>> device node of exynos_pmu_context->dev and return -EINVAL on mismatches. >>> >>> Apologies I didn't answer your original question. This wasn't about >>> having partial support for multiple pmu devices. It is being used by >>> driver_find_device_by_of_node() in exynos_get_pmu_regmap_by_phandle() >>> to determine that the exynos-pmu device has probed and therefore a >>> pmu_context exists and a regmap has been created and can be returned >>> to the caller (as opposed to doing a -EPROBE_DEFER). >>> >>> Is there some better/other API you recommend for this purpose? Just >>> checking pmu_context directly seems racy, so I don't think we should >>> do that. >> >> Hm, I don't quite get why you cannot use of_find_device_by_node()? > > of_find_device_by_node() returns a platform_device, even if the driver > hasn't probed. Whereas driver_find_device_by_of_node() iterates > devices bound to a driver. > > If using of_find_device_by_node() API I could check the result of > platform_get_drvdata(), and -EPROBE_DEFER if NULL (that pattern seems > to be used by a few drivers). But that AFAIK only guarantees you > reached the platform_set_drvdata() call in your driver probe() > function, not that it has completed. All drivers, except two, use of_find_device_by_node(), so basically you claim they are all broken. If that's true, the core API and these drivers should be fixed, instead of implementing here entirely different pattern. of_find_device_by_node() goes via platform_bus_type->sp->klist_devices and devices are added to the list in device_add() after bus_probe_device(dev), regardless of its success. Therefore after successful first probe, you will have the same result. > > IMHO the drivers using driver_find_device_by_of_node() for probe > deferral are doing it more robustly than those using > of_find_device_by_node() and checking if platform_get_drvdata() is > NULL. Some are checking dev->driver, but this also looks buggy, because it is called before actual drv->probe(). OK, let's go with this method. I dislike the difference from everyone else, but it seems everyone else is doing it wrong. :( Best regards, Krzysztof
