On Fri, Dec 20, 2013 at 08:55:27PM +0100, Pavel Machek wrote: > On Sun 2013-12-15 11:25:08, David Cohen wrote: > > On Sun, Dec 15, 2013 at 06:51:12PM +0100, Pavel Machek wrote: > > > On Thu 2013-12-12 21:18:23, David Cohen wrote: > > > > This patch makes SET_SYSTEM_SLEEP_PM_OPS() and SET_RUNTIME_PM_OPS() more > > > > smart. > > > > > > > > Despite those macros check for '#ifdef CONFIG_PM_SLEEP/RUNTIME' to avoid > > > > setting the callbacks when such #ifdef's aren't defined, they don't > > > > handle compiler to avoid messages like that: > > > > > > > > drivers/usb/host/xhci-plat.c:200:12: warning: ???xhci_plat_suspend??? defined but not used [-Wunused-function] > > > > drivers/usb/host/xhci-plat.c:208:12: warning: ???xhci_plat_resume??? defined but not used [-Wunused-function] > > > > > > > > As result, those macros get rid of #ifdef's when setting callbacks but > > > > not when implementing them. > > > > > > > > With this patch, drivers using SET_*_PM_OPS() macros don't need to #ifdef > > > > the callbacks implementation as well. > > > > > > Well... Interesting trickery, but it means that resulting kernel > > > will be bigge due to the dead functions no? > > > > Actually, it doesn't get bigger. Before sending the patch I did this > > dummy test app: > > > > -------------------------------------------------------------------------------- > > #include <stdio.h> > > > > #define USE_IT_OR_LOOSE_IT(fn) ((void *)((unsigned long)(fn) - (unsigned long)(fn))) > > > > #ifdef MAKE_ME_NULL > > static int func1(int a) > > { > > printf("Hey!!\n"); > > return 0; > > } > > #endif > > I thought that point of this patch series was getting rid of the > #ifdefs around the function...? Now I'm confused. Maybe you're misinterpreting the test :) This #ifdef is used to make this same test code to replicate both scenarios according to -DMAKE_ME_NULL (just pay attention to actual resulting code after #ifdef's are tested. the #ifdef here is nor related to actual #ifdef on kernel). Here are both scenarios: (1) Not using my trickery (which needs the function to not be present). (2) Using my trickery (which needs to function to stay). With -DMAKE_ME_NULL we replicate (2), then the function *is* there but gcc gets rid of it on resulting binary without warnings if used with -O2. Without -DMAKE_ME_NULL we replicate (1). The #ifdef will fail and then remove the function which is an obvious scenario the function won't be part of resulting binary. If we use -S option to have human readable resulting assembly code (which is kind of 1:1 for resulting binary), we can compare the result of (1) and (2) and check they are pretty similar. This proves gcc behaves as expected with my patch: do not need #ifdef and do not generate dead codes to resulting binary. > > > struct global_data { > > int (*func)(int); > > }; > > > > static struct global_data gd = { > > #ifdef MAKE_ME_NULL > > .func = USE_IT_OR_LOOSE_IT(func1), > > If you have ifdef around the function, why do you need magic here? Why > not This #ifdef is necessary to prevent the function to be used when it doesn't exist due to above #ifdef. But once again: don't misinterpret the #ifdefs in this test app with the ones in kernel. They are not related at all. If it's still confusing you just make 2 test apps without #ifdeds out of this one where one keeps the code inside #ifdefs and the other doesn't. > > .func = func1 > > ? > > Basically the warning tells you that you want the ifdef around the > function, too... (Otherwise you waste space). That seems like good > warning. Just check my first explanation. Br, David Cohen > > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html