Messages in this thread | | | Date | Tue, 3 Oct 2023 11:43:26 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH v10 1/3] nvmem: core: Rework layouts to become platform devices |
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Hi Srinivas,
> > +static int nvmem_dev_match_available_layout(struct device *dev, void *data) > > +{ > > + struct nvmem_device *nvmem = to_nvmem_device(dev); > > + > > + return nvmem_match_available_layout(nvmem); > > +} > > + > > +static int nvmem_for_each_dev(int (*fn)(struct device *dev, void *data)) > > +{ > > + return bus_for_each_dev(&nvmem_bus_type, NULL, NULL, fn); > > +} > > + > > +/* > > + * When an NVMEM device is registered, try to match against a layout and > > + * populate the cells. When an NVMEM layout is probed, ensure all NVMEM devices > > + * which could use it properly expose their cells. > > + */ > > +static int nvmem_notifier_call(struct notifier_block *notifier, > > + unsigned long event_flags, void *context) > > +{ > > + struct nvmem_device *nvmem = NULL; > > + int ret; > > + > > + switch (event_flags) { > > + case NVMEM_ADD: > > + nvmem = context; > > + break; > > + case NVMEM_LAYOUT_ADD: > > + break; > > + default: > > + return NOTIFY_DONE; > > + } > > It looks bit unnatural for core to register notifier for its own events. > > > Why do we need the notifier at core level, can we not just handle this in core before raising these events, instead of registering a notifier cb?
There is no good place to do that "synchronously". We need some kind of notification mechanism in these two cases: * A memory device is being probed -> if a matching layout driver is already available, we need to parse the device and expose the cells, but not in the thread registering the memory device. * A layout driver is being insmod'ed -> if a memory device needs it to create cells we need to parse the device content, but I find it crappy to start device-specific parsing in the registration handler.
So probe of the memory device is not a good place for this, nor is the registration of the layout driver. Yet, we need to do the same operation upon two different "events".
This notifier mechanism is a clean and easy way to get notified and implement a callback which is also not blocking the thread doing the initial registration. I am personally not bothered using it only internally. If you have another mechanism in mind to perform a similar operation, or a way to avoid this need I'll do the switch.
Thanks, Miquèl
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