On Mon, Dec 14, 2015 at 04:33:51PM +0800, Ley Foon Tan wrote: > On Mon, Dec 14, 2015 at 4:24 PM, Thierry Reding > <thierry.reding@xxxxxxxxx> wrote: > > On Mon, Dec 14, 2015 at 09:19:30AM +0100, Geert Uytterhoeven wrote: > >> Hi Paul, > >> > >> On Sun, Dec 13, 2015 at 2:41 AM, Paul Gortmaker > >> <paul.gortmaker@xxxxxxxxxxxxx> wrote: > >> > This series of commits is a slice of a larger project to ensure > >> > people don't have dead code for module removal in non-modular > >> > drivers. Overall there was roughly 5k lines of dead code in the > >> > kernel due to this. So far we've fixed several areas, like tty, > >> > x86, net, etc. and we continue to work on other areas. > >> > > >> > There are several reasons to not use module_init for code that can > >> > never be built as a module, but the big ones are: > >> > > >> > (1) it is easy to accidentally code up unused module_exit and remove code > >> > (2) it can be misleading when reading the source, thinking it can be > >> > modular when the Makefile and/or Kconfig prohibit it > >> > (3) it requires the include of the module.h header file which in turn > >> > includes nearly everything else. > >> > > >> > Here we convert some module_init() calls into device_initcall() and delete > >> > any module_exit and remove code that gets orphaned in the process, for > >> > an overall net code reduction, which is always welcome. > >> > > >> > The use of device_initcall ensures that the init function ordering > >> > remains unchanged, but one could argue that PCI host code might be more > >> > appropriate to be handled under subsys_initcall. Fortunately we can > >> > revisit making this extra change at a later date if desired; it does > >> > not need to happen now, and we reduce the risk of introducing > >> > regressions at this point in time by separating the two changes. > >> > > >> > Over half of the drivers changed here already explicitly disallowed any > >> > unbind operations. For the rest we make them the same, since there is > >> > not really any sensible use case to unbind any built-in bus support that > >> > I can think of. > >> > >> Personally, I think all of these should become tristate, so distro kernels > >> don't have to build in PCI(e) support for all SoCs. multi_v7_defconfig kernels > >> are becoming too big. > >> > >> That does not preclude making these modules un-unloadable, though. > > > > Most of these can't be made tristate as-is, because they use symbols > > that aren't exported. Many of those symbols can easily be exported, so > > its just a matter of getting the respective patches merged. I disagree > > with making the modules non-unloadable, though. I have a local branch > > with changes necessary to unload the host controller driver and it > > works just fine. > > > PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate. > Fixup region is in kernel region and this region if not updated when > loading a module. Interesting, I hadn't thought about that. I suppose this means that the module will end up containing an unused section with the fixup code. It might be useful to add a way for that to trigger a warning at build time. Perhaps to fix this a mechanism could be introduced to add a table of fixups to a host controller driver and that will get applied to all children of the bridge. It could be problematic to cover all of the different fixup stages, though. Thierry
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