On Friday 26 September 2014 10:58:33 Pankaj Dubey wrote: > On Thursday, September 25, 2014 6:12 PM, Arnd Bergmann wrote, > > I don't remember noticing the of_find_device_by_node or > > platform_device_alloc in > > earlier versions of this patch, but that could just be me failing to read > > it right. > > > Yes, till v2 of this patch set we do not used this and while calling > regmap_init_mmio, I used > NULL pointer while creating regmap handle. But as you may be remember Dong > Aisheng reported crash > on latest Linus tree after applying this patch, and it caused because of > some recent changes in > regmap which has already landed in main tree, which makes passing of dev > pointer compulsory > while calling regmap_init_mmio. Please check following commits in current > tree > > 1) d647c19 regmap: add DT endianness binding support. > 2) ba1b53f regmap: Fix DT endianess parsing logic. > 3) 45e1a27 regmap: of_regmap_get_endian() cleanup > > and following patch [1] for changing syscon binding from Xiubo Li > > [1] [PATCH] mfd: syscon: binding: Add syscon endianness support > https://lkml.org/lkml/2014/9/18/67 > > So we discussed [2] and decided to use either actual device if it's > populated and available for use or > create either actual device or dummy device for using it during > regmap_init_mmio calls. > > [2]: https://lkml.org/lkml/2014/9/18/35 > > So what I understood from these changes from Xiubo Li, they wanted to pass > endianness of regmap > handle to be passed from DT. > > So I am not sure if we can really make regmap code work without a device > pointer. Why can't we just have both a dev pointer and an explicit of_node pointer that can be used in the absence of the device? I think it's dangerous to have a platform device that is allocated but not registered as you do in your driver at the moment. We can't register it for early callers either, and if we found a way to do so, we'd end up with multiple platform devices that contain the same of_node, which would then cause other problems, such as binding both devices to the same driver. > > I think this should get removed: it would be much better to ensure that > the regmap > > code can work without a device pointer, which I thought it did. We should > probably > > also skip the creation of the debugfs directory in that case. > > > > > Also if it was just a matter of creating platform_device at early > > > stage then early initialization of syscon could have been solved till > > > now. > > As far as debugfs of regmap is concerned it can be solved as I replied to > Heiko in this thread [3] > if we are using device pointer while creating regmap handle. > If we are not using device pointer while creating regmap handle it won't > cause any problem and > there won't be any debugfs entry. > > [3]: https://lkml.org/lkml/2014/9/26/20 Right, this works, although my earlier thoughts were that we would just never have a device for a syscon any more. We could have a different representation for syscon regmaps in debugfs though, one that is separate from the devices and that is based on the just the of_node pointer. syscon is special enough that I think the regmap infrastructure should be aware of what is a syscon regmap as opposed to one from a device. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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