[OE-core] [PATCH] kernel.bbclass: Allow ${S} to be overridden

[Andre McCurdy]

On Wed, Nov 9, 2016 at 10:08 AM, Paul Barker <paul at paulbarker.me.uk> wrote:
> On Wed, 9 Nov 2016 08:09:09 -0500
> Bruce Ashfield <bruce.ashfield at gmail.com> wrote:
>
>> On Wed, Nov 9, 2016 at 5:04 AM, Burton, Ross <ross.burton at intel.com> wrote:
>>
>> >
>> > On 9 November 2016 at 02:23, Bruce Ashfield <bruce.ashfield at gmail.com>
>> > wrote:
>> >
>> >> I can ack this patch, since no defaults change .. there's no risk to
>> >> existing users.
>> >>
>> >
>> > Saying that of course doomed the patch:
>> >
>>
>> interesting.
>>
>> Paul: obviously you were building with this in place, and my local test did
>> work here
>> as well .. so any idea to the difference ?
>>
>> Let me know if you want any help looking into it.
>>
>> Cheers,
>>
>> Bruce
>>
>
> The reason for this patch is that I'm using a tarball for the kernel
> sources in the new meta-arduino layer. That tarball doesn't get
> extracted to ${STAGING_KERNEL_DIR} and so it needs to be copied over to
> there. Looking at kernel.bbclass, it looks like the logic to do this is
> present:
>
>
>     # Old style kernels may set ${S} = ${WORKDIR}/git for example
>     # We need to move these over to STAGING_KERNEL_DIR. We can't just
>     # create the symlink in advance as the git fetcher can't cope with
>     # the symlink.
>     do_unpack[cleandirs] += " ${S} ${STAGING_KERNEL_DIR} ${B} ${STAGING_KERNEL_BUILDDIR}"
>     do_clean[cleandirs] += " ${S} ${STAGING_KERNEL_DIR} ${B} ${STAGING_KERNEL_BUILDDIR}"
>     base_do_unpack_append () {
>         s = d.getVar("S", True)
>         if s[-1] == '/':
>             # drop trailing slash, so that os.symlink(kernsrc, s) doesn't use s as directory name and fail
>             s=s[:-1]
>         kernsrc = d.getVar("STAGING_KERNEL_DIR", True)
>         if s != kernsrc:
>             bb.utils.mkdirhier(kernsrc)
>             bb.utils.remove(kernsrc, recurse=True)
>             if d.getVar("EXTERNALSRC", True):
>                 # With EXTERNALSRC S will not be wiped so we can symlink to it
>                 os.symlink(s, kernsrc)
>             else:
>                 import shutil
>                 shutil.move(s, kernsrc)
>                 os.symlink(kernsrc, s)
>     }
>
> The problem is we can't set S to anything unless we can override it.
>
> I've now looked into this futher and it seems to be working for some
> kernel recipes but not others. The issue may be that we have an
> assignment for S in bitbake.conf:
>
>     S = "${WORKDIR}/${BP}"
>
> That's obviously overriding the 'S ?= ...' assignment when my patch is
> applied where S isn't also explicitly assigned in the recipe, some
> other class or include file.
>
> I'm not sure on how precedence is determined if a variable is assigned
> using '=' multiple times.
>
> I'll have another look into it and see where I get. I have a workaround
> in place for the meta-arduino layer for now so it doesn't need an
> urgent fix.
>
> However, if it turns out we can't reliably override S in a kernel recipe
> then should we still have that comment and base_do_unpack_append() in
> kernel.bbclass?

The solution I use (learned the hard way) is to ensure that "S = ..."
comes after "inherit kernel" in the kernel recipe.

> Thanks,
> Paul
> --
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