media_build: fix module_*_driver redefined warnings

  The conditions "#ifndef module_usb_driver" and "#ifndef module_platform_driver"
are always true, as the header files where this macros are defined are not
included in compat.h (linux/usb.h and linux/platform_devices.h).

This produces a lot of warnings like "module_usb_driver redefined" or
"module_platform_driver redefined" with kernels 3.2 and 3.3.

But including the header files in compat.h produces other "redefined" warnings,
so let's check the kernel version instead.

module_usb_driver was first introduced in kernel 3.3,
while module_platform_driver was introduced in kernel 3.2.

Tested with kernel 3.3, 3.2 and 3.0.

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
---
 v4l/compat.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
  

Hi Gianluca,

Em 20-03-2012 11:10, Gianluca Gennari escreveu:
> The conditions "#ifndef module_usb_driver" and "#ifndef module_platform_driver"
> are always true, as the header files where this macros are defined are not
> included in compat.h (linux/usb.h and linux/platform_devices.h).
> 
> This produces a lot of warnings like "module_usb_driver redefined" or
> "module_platform_driver redefined" with kernels 3.2 and 3.3.
> 
> But including the header files in compat.h produces other "redefined" warnings,
> so let's check the kernel version instead.
> 
> module_usb_driver was first introduced in kernel 3.3,
> while module_platform_driver was introduced in kernel 3.2.
> 
> Tested with kernel 3.3, 3.2 and 3.0.
> 
> Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
> ---
>  v4l/compat.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/v4l/compat.h b/v4l/compat.h
> index 62710c9..ab0f2e7 100644
> --- a/v4l/compat.h
> +++ b/v4l/compat.h
> @@ -864,7 +864,7 @@ static inline int snd_ctl_enum_info(struct snd_ctl_elem_info *info, unsigned int
>  #endif
>  #endif /*pr_debug_ratelimited */
>  
> -#ifndef module_usb_driver
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 3, 0)

Please avoid adding more tests for an specific Kernel version here. There are
two issues with checks like that:

	1) this may break on some kernel-fix release that might backport the function.
This is not very common, but there was some cases like that, in the USB subsystem;

	2) this generally breaks compilation, after some time, if someone tries
to compile it against a distribution-patched kernel, as the new code may be
backported there.

That's said, if just doing an "#ifdef module_usb_driver" doesn't work because this
is not a macro, you can add a simple check at this script:
	v4l/scripts/make_config_compat.pl 

like this one:

	check_file_for_func("include/linux/delay.h", "usleep_range", "NEED_USLEEP_RANGE");

This function will seek for "usleep_range" at the delay.h header. If not found, it will
add a #define NEED_USLEEP_RANGE at v4l/config-compat.h, that can be checked inside compat.h:

#ifdef NEED_USLEEP_RANGE
#define usleep_range(min, max) msleep(min/1000)
#endif

You can use the same kind of logic for module_usb_driver.

Regards,
Mauro


>  #define module_usb_driver(drv)			\
>  static int __init usb_mod_init(void)		\
>  {						\
> @@ -878,7 +878,7 @@ module_init(usb_mod_init);			\
>  module_exit(usb_mod_exit);
>  #endif /* module_usb_driver */
>  
> -#ifndef module_platform_driver
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 2, 0)
>  #define module_platform_driver(drv)		\
>  static int __init plat_mod_init(void)		\
>  {						\

--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
  

Il 09/04/2012 14:34, Mauro Carvalho Chehab ha scritto:
> Hi Gianluca,
> 
> Em 20-03-2012 11:10, Gianluca Gennari escreveu:
> 
> Please avoid adding more tests for an specific Kernel version here. There are
> two issues with checks like that:
> 
> 	1) this may break on some kernel-fix release that might backport the function.
> This is not very common, but there was some cases like that, in the USB subsystem;
> 
> 	2) this generally breaks compilation, after some time, if someone tries
> to compile it against a distribution-patched kernel, as the new code may be
> backported there.
> 
> That's said, if just doing an "#ifdef module_usb_driver" doesn't work because this
> is not a macro, you can add a simple check at this script:
> 	v4l/scripts/make_config_compat.pl 
> 
> like this one:
> 
> 	check_file_for_func("include/linux/delay.h", "usleep_range", "NEED_USLEEP_RANGE");
> 
> This function will seek for "usleep_range" at the delay.h header. If not found, it will
> add a #define NEED_USLEEP_RANGE at v4l/config-compat.h, that can be checked inside compat.h:
> 
> #ifdef NEED_USLEEP_RANGE
> #define usleep_range(min, max) msleep(min/1000)
> #endif
> 
> You can use the same kind of logic for module_usb_driver.
> 
> Regards,
> Mauro

Hi Mauro,
thanks for the explanation but Hans Verkuil already solved the issue
using the check_file_for_func method:

http://git.linuxtv.org/media_build.git/commit/2492bf186743a925db98694911649fa0e94003f5

Of course, I agree this is a much better solution.

Regards,
Gianluca
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
  

Em 09-04-2012 11:15, Gianluca Gennari escreveu:
> 
> Il 09/04/2012 14:34, Mauro Carvalho Chehab ha scritto:
>> Hi Gianluca,
>>
>> Em 20-03-2012 11:10, Gianluca Gennari escreveu:
>>
>> Please avoid adding more tests for an specific Kernel version here. There are
>> two issues with checks like that:
>>
>> 	1) this may break on some kernel-fix release that might backport the function.
>> This is not very common, but there was some cases like that, in the USB subsystem;
>>
>> 	2) this generally breaks compilation, after some time, if someone tries
>> to compile it against a distribution-patched kernel, as the new code may be
>> backported there.
>>
>> That's said, if just doing an "#ifdef module_usb_driver" doesn't work because this
>> is not a macro, you can add a simple check at this script:
>> 	v4l/scripts/make_config_compat.pl 
>>
>> like this one:
>>
>> 	check_file_for_func("include/linux/delay.h", "usleep_range", "NEED_USLEEP_RANGE");
>>
>> This function will seek for "usleep_range" at the delay.h header. If not found, it will
>> add a #define NEED_USLEEP_RANGE at v4l/config-compat.h, that can be checked inside compat.h:
>>
>> #ifdef NEED_USLEEP_RANGE
>> #define usleep_range(min, max) msleep(min/1000)
>> #endif
>>
>> You can use the same kind of logic for module_usb_driver.
>>
>> Regards,
>> Mauro
> 
> Hi Mauro,
> thanks for the explanation but Hans Verkuil already solved the issue
> using the check_file_for_func method:
> 
> http://git.linuxtv.org/media_build.git/commit/2492bf186743a925db98694911649fa0e94003f5

Yeah, I noticed when I've updated it to apply a patch for Debian handling. Anyway,
I hope that the explanation is useful for you and others, as this way means less
headache on maintaining backward compatibility.

> Of course, I agree this is a much better solution.
> 
> Regards,
> Gianluca

Regards,
Mauro

--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html