Hi Hans,
On 2018-05-11 09:41, Hans Verkuil wrote:
> Hi Brad,
>
> On 04/26/18 19:19, Brad Love wrote:
>> config-mycompat.h is for overriding macros which are incorrectly
>> enabled on certain kernels by the build system. The file should be
>> left empty, unless build errors are encountered for a kernel. The
>> file is removed by distclean, therefore should be externally
>> sourced, before the build process starts, when required.
>>
>> In standard operation the file is empty, but if a particular kernel has
>> incorrectly enabled options defined this allows them to be undefined.
> Can you give an example where this will be used?
>
> FYI: I've committed patches 1-6, but I don't quite understand when this patch
> is needed.
>
> With "for overriding macros which are incorrectly enabled on certain kernels"
> do you mean when distros do backports of features from later kernels?
>
> Regards,
>
> Hans
Apologies if I was not very clear. Yes, this is for use in
kernels/distros whose maintainers have integrated various backports, and
which the media_build system does not pick up on for whatever reason. At
that point there are options defined in config-compat.h, which enable
backports in compat.h, but which already exist in the target kernel.
For example, on the device I'm working on right now, in kernel 3.10, I
have to supply the following three options in config-mycompat.h or
modify the tree and stuff them right into the top of compat.h:
#undef NEED_WRITEL_RELAXED
#undef NEED_PM_RUNTIME_GET
#undef NEED_PFN_TO_PHYS
The above disables those three media_build backports and allows
everything to build. It seems there is quite often at least one backport
I must disable, and some target kernels require multiple backports disabled.
Cheers,
Brad
>
>> Signed-off-by: Brad Love <brad@xxxxxxxxxxxxxxxx>
>> ---
>> v4l/Makefile | 3 ++-
>> v4l/compat.h | 7 +++++++
>> 2 files changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/v4l/Makefile b/v4l/Makefile
>> index 270a624..ee18d11 100644
>> --- a/v4l/Makefile
>> +++ b/v4l/Makefile
>> @@ -273,6 +273,7 @@ links::
>> @find ../linux/drivers/misc -name '*.[ch]' -type f -print0 | xargs -0n 255 ln -sf --target-directory=.
>>
>> config-compat.h:: $(obj)/.version .myconfig scripts/make_config_compat.pl
>> + -touch $(obj)/config-mycompat.h
>> perl scripts/make_config_compat.pl $(SRCDIR) $(obj)/.myconfig $(obj)/config-compat.h
>>
>> kernel-links makelinks::
>> @@ -298,7 +299,7 @@ clean::
>> distclean:: clean
>> -rm -f .version .*.o.flags .*.o.d *.mod.gcno Makefile.media \
>> Kconfig Kconfig.kern .config .config.cmd .myconfig \
>> - .kconfig.dep
>> + .kconfig.dep config-mycompat.h
>> -rm -rf .tmp_versions .tmp*.ver .tmp*.o .*.gcno .cache.mk
>> -rm -f scripts/lxdialog scripts/kconfig
>> @find .. -name '*.orig' -exec rm '{}' \;
>> diff --git a/v4l/compat.h b/v4l/compat.h
>> index 87ce401..db48fdf 100644
>> --- a/v4l/compat.h
>> +++ b/v4l/compat.h
>> @@ -8,6 +8,13 @@
>> #include <linux/version.h>
>>
>> #include "config-compat.h"
>> +/* config-mycompat.h is for overriding #defines which
>> + * are incorrectly enabled on certain kernels. The file
>> + * should be left empty, unless build errors are encountered
>> + * for a kernel. The file is removed by distclean, therefore
>> + * should be externally sourced, before compilation, when required.
>> + */
>> +#include "config-mycompat.h"
>>
>> #ifndef SZ_512
>> #define SZ_512 0x00000200
>>
