On Tue, 4 Jun 2013 17:24:51 -0500, Rob Herring <robherri...@gmail.com> wrote: > On Tue, Jun 4, 2013 at 12:51 PM, Arnd Bergmann <a...@arndb.de> wrote: > > On Tuesday 04 June 2013, Rob Herring wrote: > >> On Sat, Jun 1, 2013 at 3:57 PM, Arnd Bergmann <a...@arndb.de> wrote: > >> > On Saturday 01 June 2013, Rob Herring wrote: > >> >> No, we still need empty functions. Here is what of_device.h looks like: > >> >> > >> >> http://tinyurl.com/l2azz5m > >> >> > >> >> BTW, it has your ack. > >> >> > >> > > >> > Could you add a patch on top that only puts the function declarations > >> > inside of #ifdef that don't have an inline wrapper? > >> > >> I'm confused. You mean that DO have an inline? Like this: > >> > >> void foo(void); > >> > >> #ifdef CONFIG_OF > >> void bar(void); > >> #else > >> static inline void bar(void) {} > >> #endif > > > > Yes, sorry. That's what I meant. > > > >> > It's really annoying to have to change the header file every time one > >> > needs to call a function from a driver in the DT-only case. > >> > >> The functions without inlines are ones that drivers should not call > >> and should only be called from OF enabled code. That's why we have not > >> done a complete pass of adding inlines for everything. > > > > The problem is that it's a bad default. The convention in kernel code > > is not to hide declarations in #ifdef, for multiple reasons: > > > > * It avoids unnecessary code rebuilds when the symbol changes between > > two 'make' runs. > > > > * It lets drivers and platform code call the function from dead code > > without causing a build error, thus improving compile coverage. > > > > * It's much nicer to read when can write your code like > > > > void __init exynos_init_io(struct map_desc *mach_desc, int size) > > { > > if (IS_ENABLED_(CONFIG_OF) && initial_boot_params) > > of_scan_flat_dt(exynos_fdt_map_chipid, NULL); > > else > > iotable_init(exynos_iodesc, ARRAY_SIZE(exynos_iodesc)); > > ... > > } > > > > instead of > > > > void __init exynos_init_io(struct map_desc *mach_desc, int size) > > { > > #ifdef CONFIG_OF > > if (initial_boot_params) > > of_scan_flat_dt(exynos_fdt_map_chipid, NULL); > > else > > #endif > > iotable_init(exynos_iodesc, ARRAY_SIZE(exynos_iodesc)); > > ... > > }
A big part of the reason for not having the headers was to discourage code like the above; so instead of having a whole bunch of DT functions inline in a drivers probe hook, they would be collected off in a DT parse function that can all get compiled away as a block. However, that's the first time I've thought about the code coverage issue and it is a good point. > > > > The first one looks like actual C code, the second is really ugly, > > and an inline wrapper wouldn't even do the right thing here. > > Right. I get all that. You still have to go add inlines if you want to make: > > if (IS_ENABLED(CONFIG_OF)) > of_foo(); > > just be: > > of_foo(); > > There are situations for both and only inlines cover both cases. I > don't see a reason we would want to allow the first case and not allow > the second case. I am tired of taking patches adding the inlines 1 by > 1, so perhaps we need to refactor the OF headers to better separate > core infrastructure includes vs. driver only includes if that is > really a concern. I'm fine with that. Attitudes have changed quite a bit in the last few years about DT code in device drivers so it isn't as important to make a hard distinction about when DT functions can be called. g. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
