[yocto] NooB: applying new patches to older files, where do I find the older files?

[R]

On 31-10-2019 01:52, Randy MacLeod wrote:
> On 10/30/19 8:16 AM, R wrote:
>> Hello List,
>>
>> First I'm working on a unsupported distro (Manjaro) and try to get an 
>> older version (2.7.1) of poky working. I have ask a question before 
>> and Ross Burton pointed me in the direction of a patch.
>> Now I'm trying to apply that patch, however the patch is for a newer 
>> version of the original files, so I need to make my own patch for the 
>> older version of these files.
>> (reason: WARNING: Some of the context lines in patches were ignored. 
>> This can lead to incorrectly applied patches.)
>>
>> The patch says: the file to be patch is e.g. /linux-user/syscall.c
>> My question is where can I find the original syscall.c before any 
>> patches are applied to it?
>
> Hi Robert,
>
> This file and the patch are for the qemu package.
>
> You can run:
> $ bitbake -c patch qemu-native <--- host build
> or
> $ bitbake -c patch qemu <--- target build
> to get all the patches that are listed in the qemu recipe in poky:
>    meta/recipes-devtools/qemu/qemu_3.1.1.1.bb
> and
>    meta/recipes-devtools/qemu/qemu.inc
> applied to unpacked source.
>
> The patched source will be in (this is on master branch):
>
> <build_area>/tmp-glibc/work/x86_64-linux/qemu-native/4.1.0-r0/qemu-4.1.0/linux-user/syscall.c 
>
>
> poky might just be /tmp/ instead of /tmp-glibc/
>
> In my case the log of the patching is in:
> tmp-glibc/work/x86_64-linux/qemu-native/4.1.0-r0/temp/log.do_patch
>
>>
>> Just to be complete: I have tried the latest warrior branch and that 
>> worked fine. My objective is not just to get it working be also to 
>> get a grip on how the system works :-)
>
> Super.
>
> Have you looked at:
> https://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html
>
> and perhaps:
>
> https://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html#finding-the-temporary-source-code 
>
>
> will be useful now.
>
> Manipulating patches by hand can be tedious. There's a tool
> called wiggle:
>    https://linux.die.net/man/1/wiggle
> which can help but may be too much for you to deal with initially.
>
> Actually, I suggest that you build on a supported distro initially
> to understand the basic workflow and then decide if you want to figure
> out how to make Arch/Manjaro work.
>
> ../Randy
>
>> Thanks,
>> Robert.

Thanks Randy,
Very helpful, especially the trigger to look into the development manual.
I know starting with a supported distro would be the smarter choice. But 
then it would just work and I would probably make tiny steps in changes, 
this way I'm pulled right into the belly of the "beast" and I will learn 
much faster how it works :-) Disadvantage is that I maybe overwhelmed, 
so I will ask a question like this one, occasionally.
Robert