From: Barry Song <21cnbao@gmail.com> To: Linus Walleij <linus.walleij@linaro.org> Cc: Linus Walleij <linus.walleij@stericsson.com>, Grant Likely <grant.likely@secretlab.ca>, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Lee Jones <lee.jones@linaro.org>, Jonas Aaberg <jonas.aberg@stericsson.com> Subject: Re: [PATCH 02/10] mach-u300: rewrite gpio driver, move to drivers/gpio Date: Thu, 19 May 2011 20:35:59 +0800 [thread overview] Message-ID: <BANLkTim2rv9QHDd2zjBfyVqG9dSGCM=PAw@mail.gmail.com> (raw) In-Reply-To: <BANLkTik7BnJKWCsm2L3-GJPTaaiXFNSgaA@mail.gmail.com> 2011/5/19 Linus Walleij <linus.walleij@linaro.org>: > On Thu, May 19, 2011 at 1:38 PM, Barry Song <21cnbao@gmail.com> wrote: > >>> -arch_initcall(u300_gpio_init); >>> -module_exit(u300_gpio_exit); >>> >> looks like the driver can't be a real module, is the module_exit >> suitable? it looks strange module_exit plays together with >> arch_initcall. > > It's a rather common design pattern in the kernel for early > platform drivers. Either the dependencies are resolved by the > different initlevels or they are resolved in probe order with > loadable modules. Module load will call all initlevels in order. > > It is not elegant but it is common. Linus, thanks for your reply. module_exit and related functions are really useless codes. but people have done that before, then we have no way except following. u300_gpio_exit never gets chance to run and when we disassemble vmlinux, u300_gpio_exit() function should be not in the final binary at all, just a symbol name is left. > >> guess symbol u300_gpio_exit will finally lose in the last vmlinux >> since it is in exit section and built-in kernel. > > Yes. And if you one day, to do some testing, compile and load it > as module and unload it, it is handy. > > I have other drivers where I simply don't have an exit function > but this one I have actually used. > >> another problem i see is after moving gpio/pinmux to drivers as >> platform device, codes in arch/arm/plat(mach) can't call gpio/pinmux >> api before the related platform devices registerred. that will >> required these platform devices enter system earlier. > > This is exactly the reason why the u300 gpio driver needs to > be initialized in an arch_initcall(). > > Yours, > Linus Walleij >
WARNING: multiple messages have this Message-ID (diff)
From: 21cnbao@gmail.com (Barry Song) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 02/10] mach-u300: rewrite gpio driver, move to drivers/gpio Date: Thu, 19 May 2011 20:35:59 +0800 [thread overview] Message-ID: <BANLkTim2rv9QHDd2zjBfyVqG9dSGCM=PAw@mail.gmail.com> (raw) In-Reply-To: <BANLkTik7BnJKWCsm2L3-GJPTaaiXFNSgaA@mail.gmail.com> 2011/5/19 Linus Walleij <linus.walleij@linaro.org>: > On Thu, May 19, 2011 at 1:38 PM, Barry Song <21cnbao@gmail.com> wrote: > >>> -arch_initcall(u300_gpio_init); >>> -module_exit(u300_gpio_exit); >>> >> looks like the driver can't be a real module, is the module_exit >> suitable? it looks strange module_exit plays together with >> arch_initcall. > > It's a rather common design pattern in the kernel for early > platform drivers. Either the dependencies are resolved by the > different initlevels or they are resolved in probe order with > loadable modules. Module load will call all initlevels in order. > > It is not elegant but it is common. Linus, thanks for your reply. module_exit and related functions are really useless codes. but people have done that before, then we have no way except following. u300_gpio_exit never gets chance to run and when we disassemble vmlinux, u300_gpio_exit() function should be not in the final binary at all, just a symbol name is left. > >> guess symbol u300_gpio_exit will finally lose in the last vmlinux >> since it is in exit section and built-in kernel. > > Yes. And if you one day, to do some testing, compile and load it > as module and unload it, it is handy. > > I have other drivers where I simply don't have an exit function > but this one I have actually used. > >> another problem i see is after moving gpio/pinmux to drivers as >> platform device, codes in arch/arm/plat(mach) can't ?call gpio/pinmux >> api before the related platform devices registerred. that will >> required these platform devices enter system earlier. > > This is exactly the reason why the u300 gpio driver needs to > be initialized in an arch_initcall(). > > Yours, > Linus Walleij >
next prev parent reply other threads:[~2011-05-19 12:36 UTC|newest] Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-04-27 13:13 [PATCH 02/10] mach-u300: rewrite gpio driver, move to drivers/gpio Linus Walleij 2011-04-27 13:13 ` Linus Walleij 2011-04-27 18:23 ` H Hartley Sweeten 2011-04-27 18:23 ` H Hartley Sweeten 2011-04-28 7:07 ` Linus Walleij 2011-04-28 7:07 ` Linus Walleij 2011-04-28 7:10 ` Linus Walleij 2011-04-28 7:10 ` Linus Walleij 2011-04-28 17:41 ` H Hartley Sweeten 2011-04-28 17:41 ` H Hartley Sweeten 2011-05-13 14:51 ` Linus Walleij 2011-05-13 14:51 ` Linus Walleij 2011-05-19 8:56 ` Shawn Guo 2011-05-19 8:56 ` Shawn Guo 2011-05-19 12:21 ` Linus Walleij 2011-05-19 12:21 ` Linus Walleij 2011-05-19 13:56 ` Shawn Guo 2011-05-19 13:56 ` Shawn Guo 2011-05-19 19:11 ` Sascha Hauer 2011-05-19 19:11 ` Sascha Hauer 2011-05-19 19:30 ` Nicolas Pitre 2011-05-19 19:30 ` Nicolas Pitre 2011-05-20 3:18 ` Shawn Guo 2011-05-20 3:18 ` Shawn Guo 2011-05-20 3:43 ` Kyungmin Park 2011-05-20 3:43 ` Kyungmin Park 2011-05-20 3:54 ` Nicolas Pitre 2011-05-20 3:54 ` Nicolas Pitre 2011-05-19 21:18 ` H Hartley Sweeten 2011-05-19 21:18 ` H Hartley Sweeten 2011-05-20 1:50 ` Jamie Iles 2011-05-20 1:50 ` Jamie Iles 2011-05-20 22:07 ` H Hartley Sweeten 2011-05-20 22:07 ` H Hartley Sweeten 2011-05-21 13:03 ` Jamie Iles 2011-05-21 13:03 ` Jamie Iles 2011-05-20 7:01 ` Grant Likely 2011-05-20 7:01 ` Grant Likely 2011-05-20 7:47 ` Linus Walleij 2011-05-20 7:47 ` Linus Walleij 2011-05-19 11:11 ` Barry Song 2011-05-19 11:38 ` Barry Song 2011-05-19 11:38 ` Barry Song 2011-05-19 12:25 ` Linus Walleij 2011-05-19 12:25 ` Linus Walleij 2011-05-19 12:35 ` Barry Song [this message] 2011-05-19 12:35 ` Barry Song 2011-05-19 13:17 ` Linus Walleij 2011-05-19 13:17 ` Linus Walleij 2011-05-19 14:05 ` Barry Song 2011-05-19 14:05 ` Barry Song 2011-05-20 6:58 ` Grant Likely 2011-05-20 6:58 ` Grant Likely 2011-05-20 6:52 ` Grant Likely 2011-05-20 6:52 ` Grant Likely 2011-05-20 7:46 ` Linus Walleij 2011-05-20 7:46 ` Linus Walleij
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