Understanding kernel patching in linux-yocto

["Yann Dirson" <yann.dirson@blade-group.com>]

I am currently working on a kmeta BSP for the rockchip-based NanoPI M4
[1], and I'm wondering how I should be providing kernel patches, as
just add ing "patch" directives in the .scc does not get them applied
unless the particular .scc gets included in KERNEL_FEATURES (see [2]).

From an old thread [3] I understand that the patches from the standard
kmeta snippets are already applied to the tree, and that to get the
patches from my BSP I'd need to reference it explicitly in SRC_URI
(along with using "nopatch" in the right places to avoid the
already-applied patches to get applied twice).

I have the feeling that I'm lacking the rationale behind this, and
would need to understand this better to make things right in this BSP.
Especially:
- at first sight, having the patches both applied to linux-yocto and
referenced in yocto-kernel-cache just to be skipped on parsing looks
like both information duplication and parsing of unused lines
- kernel-yocto.bbclass does its own generic job of locating a proper
BSP using the KMACHINE/KTYPE/KARCH tags in BSP, it looks like
specifying a specific BSP file would just defeat of this: how should I
deal with this case where I'm providing both "standard" and "tiny"
KTYPE's ?

[1] https://lists.yoctoproject.org/g/yocto/message/53454
[2] https://lists.yoctoproject.org/g/yocto/message/53452
[3] https://lists.yoctoproject.org/g/yocto/topic/61340326

Best regards,
-- 
Yann Dirson <yann@blade-group.com>
Blade / Shadow -- http://shadow.tech