Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Sun, Oct 12, 2014 at 07:51:46AM +0200, Wolfram Sang wrote: I missed the one code path you pointed out, and that should be fixed, but that doesn't mean that the original patch should be reverted, as it is the way we want things to be, let's just fix up the bug and move on. OK, that is a clear statement. So, what is your opinion on the original cleanup series removing unnecessary '.owner = THIS_MODULE' lines in drivers? Helpful? Noise? Helpful, please do it. I can take it all through my driver-core tree if you want, that might make things easier for others. greg k-h ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
So, what is your opinion on the original cleanup series removing unnecessary '.owner = THIS_MODULE' lines in drivers? Helpful? Noise? Helpful, please do it. I can take it all through my driver-core tree if you want, that might make things easier for others. Thanks, that might make sense this time. So, I'll prepare the bugfixes, add the semantic patch, add this all to my series and respin. It might take a few days because of ELCE in Düsseldorf, but I'll certainly do it. signature.asc Description: Digital signature ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. Right, this seems to be a preexisting bug. platform_create_bundle and platform_driver_probe will both overwrite the .owner field with NULL since they live in builtin code. They need to be replaced with __platform_driver_probe and __platform_driver_register that both take an extra owner argument passed down from the caller in the driver module. Yeah, that would be one solution. However, my personal favourite would meanwhile be to revert the commit that Russell mentioned. I think it is cleaner to have the owner explicitly set in the module rather than hidden away by a function call. However, grepping through include/linux, there are a few subsystems hiding it this way. So, it is a pattern somewhow. Oh well... signature.asc Description: Digital signature ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Sat, Oct 11, 2014 at 06:56:51PM +0200, Wolfram Sang wrote: You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. Right, this seems to be a preexisting bug. platform_create_bundle and platform_driver_probe will both overwrite the .owner field with NULL since they live in builtin code. They need to be replaced with __platform_driver_probe and __platform_driver_register that both take an extra owner argument passed down from the caller in the driver module. Yeah, that would be one solution. However, my personal favourite would meanwhile be to revert the commit that Russell mentioned. I think it is cleaner to have the owner explicitly set in the module rather than hidden away by a function call. However, grepping through include/linux, there are a few subsystems hiding it this way. So, it is a pattern somewhow. Oh well... It really /ought/ to be consistent, because inconsistencies like that will be a never-ending source of subtle mistakes. Imagine what it would be like if the kernel was a complete mess of functions with return type int where there was no predominant pattern of returning negative errno numbers - where it was random whether int-returning functions returned zero for failure, others returned zero for success. We would have to look up every single function to check it's return style, and it would be a bigger problem when reviewing code. There is a lot of value for saving time and reducing errors to have a consistent, simple and obvious methodology. (That's not to say that it should be enforced draconian style - but there'd better be a good reason to be different, rather than I think it's better this way or my personal style is different.) -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Sat, Oct 11, 2014 at 06:56:51PM +0200, Wolfram Sang wrote: You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. Right, this seems to be a preexisting bug. platform_create_bundle and platform_driver_probe will both overwrite the .owner field with NULL since they live in builtin code. They need to be replaced with __platform_driver_probe and __platform_driver_register that both take an extra owner argument passed down from the caller in the driver module. Yeah, that would be one solution. However, my personal favourite would meanwhile be to revert the commit that Russell mentioned. I think it is cleaner to have the owner explicitly set in the module rather than hidden away by a function call. However, grepping through include/linux, there are a few subsystems hiding it this way. So, it is a pattern somewhow. Oh well... The pattern is to not have to manually set MODULE_OWNER, and have the pre-processor do it for you, otherwise you will forget or get it wrong. That is why I accepted this patch to the platform driver interface, as it is in line with many other bus driver apis (pci, usb, etc.). I missed the one code path you pointed out, and that should be fixed, but that doesn't mean that the original patch should be reverted, as it is the way we want things to be, let's just fix up the bug and move on. And again, may I just say how much I hate the platform driver code, one of these days I'm going to lock myself in a room for a week and figure out a way to just delete that stuff... greg k-h ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
[Cocci] [RFC] drop owner assignment from platform_drivers
Hi,
people found out that for platform_driver, we don't need to set the
.owner field because this is done by the platform driver core. So far,
so good. However, now I got patches removing the .owner field for this
single i2c driver or for that one. To prevent getting thousands of
patches fixing single drivers, I used coccinelle to remove all instances
from the kernel. The SmPL looks like this, it doesn't blindly remove all
THIS_MODULE, but checks if the platform_driver struct was really used by
a call actually setting the .owner field:
===
@match1@
declarer name module_platform_driver;
declarer name module_platform_driver_probe;
identifier __driver;
@@
(
module_platform_driver(__driver);
|
module_platform_driver_probe(__driver, ...);
)
@fix1 depends on match1@
identifier match1.__driver;
@@
static struct platform_driver __driver = {
.driver = {
- .owner = THIS_MODULE,
}
};
@match2@
identifier __driver;
@@
(
platform_driver_register(__driver)
|
platform_driver_probe(__driver, ...)
|
platform_create_bundle(__driver, ...)
)
@fix2 depends on match2@
identifier match2.__driver;
@@
static struct platform_driver __driver = {
.driver = {
- .owner = THIS_MODULE,
}
};
===
I tried to group the changes. The current granularity is directory
level. The resulting branch can be found here (it is based on linux-next
of yesterday):
git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git
drop_platform_driver_owner
This still results in 300 patches as this shortened pull request shows:
===
Wolfram Sang (299):
ARM: common: drop owner assignment from platform_drivers
ARM: mach-davinci: drop owner assignment from platform_drivers
ARM: mach-imx: drop owner assignment from platform_drivers
...
ASoC: txx9: drop owner assignment from platform_drivers
ASoC: ux500: drop owner assignment from platform_drivers
ALSA: sparc: drop owner assignment from platform_drivers
arch/arm/common/sa.c | 1 -
arch/arm/mach-davinci/cpuidle.c | 1 -
arch/arm/mach-davinci/pm.c | 1 -
...
sound/sparc/amd7930.c| 1 -
sound/sparc/cs4231.c | 1 -
sound/sparc/dbri.c | 1 -
1688 files changed, 1718 deletions(-)
===
I don't want to send all 300 patches to lkml. I still think, they should
go via subsystems, though, and not via a single pull request. So, I am
working on just sending smaller pieces of this huge series to the
apropriate mailing lists (like arm, netdev...) as an independent series.
Then, each subsystem can decide if the patches should be further folded.
In my experience, this mileage varies from subsystem to subsystem.
That's my plan for today. If you have comments, other suggestions or
remarks, I'd like to hear them.
Thanks,
Wolfram
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Re: [Cocci] [RFC] drop owner assignment from platform_drivers
@match1@
declarer name module_platform_driver;
declarer name module_platform_driver_probe;
identifier __driver;
@@
(
module_platform_driver(__driver);
|
module_platform_driver_probe(__driver, ...);
)
@fix1 depends on match1@
identifier match1.__driver;
@@
static struct platform_driver __driver = {
.driver = {
- .owner = THIS_MODULE,
}
};
@match2@
identifier __driver;
@@
(
platform_driver_register(__driver)
|
platform_driver_probe(__driver, ...)
|
platform_create_bundle(__driver, ...)
)
@fix2 depends on match2@
identifier match2.__driver;
@@
static struct platform_driver __driver = {
.driver = {
- .owner = THIS_MODULE,
}
};
The semantic patch looks fine. I'm a little surprised that it doesn't
complain about the lack of a comma after
.driver = { .owner = THIS_MODULE, }
but it seems that it does not.
If you think that it would be useful to have this in the Linux kernel, so
people don't add the owner initializer back in the future, you can try
coccinelle/tools/sgen/sgen
(run make in the coccinelle/tools/sgen directory). That will guide you
through the process of making a Linux-ready semantic patch. Feedback
would be appreciated.
julia
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Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Friday 10 October 2014 09:24:39 Wolfram Sang wrote: people found out that for platform_driver, we don't need to set the .owner field because this is done by the platform driver core. So far, so good. However, now I got patches removing the .owner field for this single i2c driver or for that one. To prevent getting thousands of patches fixing single drivers, I used coccinelle to remove all instances from the kernel. The SmPL looks like this, it doesn't blindly remove all THIS_MODULE, but checks if the platform_driver struct was really used by a call actually setting the .owner field: Is the intention just to save a few lines in the kernel source, or are there any additional upsides to doing this? While it looks like an obvious cleanup, it also seems to me that there is zero effect in terms of functionality, code size or enabling future changes. I'm all for adding your semantic patch to scripts/coccinelle so it gets picked up by anyone writing new drivers or doing code cleanup on their driver, but I'm unsure about the value of applying all your patches for the existing drivers. Arnd ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
The semantic patch looks fine. Wow, nothing to improve on the semantic patch? Now I am proud :) Thanks Julia for your support, as always! If you think that it would be useful to have this in the Linux kernel, so people don't add the owner initializer back in the future, you can try coccinelle/tools/sgen/sgen Will try later this weekend, thanks! signature.asc Description: Digital signature ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
Hi Arnd, thanks for taking a look! On Fri, Oct 10, 2014 at 10:30:08AM +0200, Arnd Bergmann wrote: On Friday 10 October 2014 09:24:39 Wolfram Sang wrote: people found out that for platform_driver, we don't need to set the .owner field because this is done by the platform driver core. So far, so good. However, now I got patches removing the .owner field for this single i2c driver or for that one. To prevent getting thousands of patches fixing single drivers, I used coccinelle to remove all instances from the kernel. The SmPL looks like this, it doesn't blindly remove all THIS_MODULE, but checks if the platform_driver struct was really used by a call actually setting the .owner field: Is the intention just to save a few lines in the kernel source, or are there any additional upsides to doing this? As written above, I don't like getting patches removing this line for single drivers. I already got two and I am expecting more. So I'd prefer to do this on subsystem level. I will apply the I2C part, for sure. While it looks like an obvious cleanup, it also seems to me that there is zero effect in terms of functionality, code size or enabling future changes. Well, the kernel image will compress better ;) And well, it is cleaner. Why should we set up something if it gets overwritten anyhow? I'm all for adding your semantic patch to scripts/coccinelle so it gets picked up by anyone writing new drivers or doing code cleanup on their driver, but I'm unsure about the value of applying all your patches for the existing drivers. I could try reducing the number of patches. Any other downsides? Thanks, Wolfram signature.asc Description: Digital signature ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Fri, Oct 10, 2014 at 09:36:27AM +0100, Russell King - ARM Linux wrote: On Fri, Oct 10, 2014 at 09:24:39AM +0200, Wolfram Sang wrote: people found out that for platform_driver, we don't need to set the .owner field because this is done by the platform driver core. So far, so good. However, now I got patches removing the .owner field for this single i2c driver or for that one. To prevent getting thousands of patches fixing single drivers, I used coccinelle to remove all instances from the kernel. The SmPL looks like this, it doesn't blindly remove all THIS_MODULE, but checks if the platform_driver struct was really used by a call actually setting the .owner field: Is this correct? #define platform_driver_register(drv) \ __platform_driver_register(drv, THIS_MODULE) extern int __platform_driver_register(struct platform_driver *, struct module *); Fine for those which use platform_driver_register(), but: /* non-hotpluggable platform devices may use this so that probe() and * its support may live in __init sections, conserving runtime memory. */ extern int platform_driver_probe(struct platform_driver *driver, int (*probe)(struct platform_device *)); platform_driver_probe() doesn't seem to know which module called it. This is also true of platform_create_bundle: extern struct platform_device *platform_create_bundle( struct platform_driver *driver, int (*probe)(struct platform_device *), struct resource *res, unsigned int n_res, const void *data, size_t size); So, it's not as trivial as just all platform driver's should not have a .owner field - the real answer is far more complex than that. platform_create_bundle() calls platform_driver_probe(). platform_driver_probe() calls platform_driver_register(). platform_driver_register() modifies driver.owner. So, it is correct from the point of view that it doesn't make sense to set the .owner field if it gets overwritten anyhow. You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. Thanks, Wolfram signature.asc Description: Digital signature ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Friday 10 October 2014 20:26:05 Wolfram Sang wrote: You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. Right, this seems to be a preexisting bug. platform_create_bundle and platform_driver_probe will both overwrite the .owner field with NULL since they live in builtin code. They need to be replaced with __platform_driver_probe and __platform_driver_register that both take an extra owner argument passed down from the caller in the driver module. Arnd ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [RFC] drop owner assignment from platform_drivers
On Fri, Oct 10, 2014 at 08:26:05PM +0200, Wolfram Sang wrote: platform_create_bundle() calls platform_driver_probe(). platform_driver_probe() calls platform_driver_register(). platform_driver_register() modifies driver.owner. So, it is correct from the point of view that it doesn't make sense to set the .owner field if it gets overwritten anyhow. You got me wondering, though, that it could not be correct to call platform_driver_register() from the platform core instead of module init. I will check tomorrow. Still, this would be a bug independent of my series. Although I'd need to respin it if platform_driver_probe() needed a fix. This shows what the bad side-effect of people doing cleanups is. This bug was introduced by: commit 9447057eaff871dd7c63c808de761b8732407169 Author: Libo Chen clbchenlibo.c...@huawei.com Date: Sat May 25 12:40:50 2013 +0800 platform_device: use a macro instead of platform_driver_register I found a lot of mistakes using struct platform_driver without owner so I make a macro instead of the function platform_driver_register. It can set owner in it, then guys don`t care about module owner again. Signed-off-by: Libo Chen libo.c...@huawei.com Signed-off-by: Greg Kroah-Hartman gre...@linuxfoundation.org So, this patch subsituted one set of mistakes for another mistake... -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
