From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Cohen Subject: Re: [RFC/PATCH 1/3] pm: make PM macros more smart Date: Sun, 15 Dec 2013 11:25:08 -0800 Message-ID: <20131215192508.GA10514@psi-dev26.jf.intel.com> References: <1386911905-2366-1-git-send-email-david.a.cohen@linux.intel.com> <1386911905-2366-2-git-send-email-david.a.cohen@linux.intel.com> <20131215175112.GA23298@Nokia-N900> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20131215175112.GA23298@Nokia-N900> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Machek Cc: rjw@rjwysocki.net, len.brown@intel.com, sarah.a.sharp@linux.intel.com, gregkh@linuxfoundation.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, santosh.shilimkar@ti.com List-Id: linux-pm@vger.kernel.org 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 #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 struct global_data { int (*func)(int); }; static struct global_data gd = { #ifdef MAKE_ME_NULL .func = USE_IT_OR_LOOSE_IT(func1), #endif }; int main(void) { #ifdef MAKE_ME_NULL printf("MAKE_ME_NULL is defined\n"); #else printf("MAKE_ME_NULL is NOT defined\n"); #endif printf("%p\n", gd.func); return 0; } -------------------------------------------------------------------------------- Then I compiled 2 .S files: $ gcc -DMAKE_ME_NULL test1.c -O2 -S -o test_makemenull.S $ gcc test1.c -O2 -S -o test_no_makemenull.S This is the diff between both: -------------------------------------------------------------------------------- --- test_makemenull.S 2013-12-15 11:07:02.635992492 -0800 +++ test_no_makemenull.S 2013-12-15 11:07:10.639992359 -0800 @@ -1,7 +1,7 @@ .file "test1.c" .section .rodata.str1.1,"aMS",@progbits,1 .LC0: - .string "MAKE_ME_NULL is defined" + .string "MAKE_ME_NULL is NOT defined" .LC1: .string "%p\n" .section .text.startup,"ax",@progbits @@ -9,7 +9,7 @@ .globl main .type main, @function main: -.LFB12: +.LFB11: .cfi_startproc subq $8, %rsp .cfi_def_cfa_offset 16 @@ -24,7 +24,7 @@ .cfi_def_cfa_offset 8 ret .cfi_endproc -.LFE12: +.LFE11: .size main, .-main .ident "GCC: (Debian 4.8.2-1) 4.8.2" .section .note.GNU-stack,"",@progbits -------------------------------------------------------------------------------- My conclusion is gcc's -O2 handles this situation pretty well, which makes my patch to have not much actual side effects on kernel binary. Br, David Cohen > > That may be acceptable tradeoff, but I guess its worth discussing... > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html