[Buildroot] linux.mk: custom tarball: re-download if tarball changed

Thomas De Schampheleire patrickdepinguin+buildroot at gmail.com
Wed Sep 14 10:16:47 UTC 2011

On Wed, Jul 20, 2011 at 3:20 PM, Thomas De Schampheleire
<patrickdepinguin+buildroot at gmail.com> wrote:
> Hi,
> If you use a vanilla kernel, and you upstep your kernel, buildroot
> automatically downloads and compiles the new version, because
> LINUX26_DIR changed, and the .stamp_downloaded file is not yet present
> in that new directory.
> When you specify a LINUX26_TARBALL, the variable LINUX26_VERSION will
> be set to the fixed "custom". As a result, LINUX26_DIR remains the
> same even though you modified the .config file to specify a different
> tarball.  When re-running make, buildroot does not see the change, and
> you'll have to force building the new kernel.
> How can we make sure that buildroot notices this change in configuration?
> One way would be to step away from the fixed 'custom' version string,
> and encode the tarball name in some way in LINUX26_DIR.
> Another possibility is to let the download step depend on the tarball.
> If the tarball changes, then make will initiate the download step.
> In buildroot-2011.05, I applied the following (working) patch
> implementing the second alternative:
> linux: depend on source archive so that updates to custom tarballs are picked up
> diff --git a/linux/linux.mk b/linux/linux.mk
> --- a/linux/linux.mk
> +++ b/linux/linux.mk
> @@ -75,9 +75,14 @@ endif
>  # Download
> -$(LINUX26_DIR)/.stamp_downloaded:
>        @$(call MESSAGE,"Downloading kernel")
>        $(call DOWNLOAD,$(LINUX26_SITE),$(LINUX26_SOURCE))
> +
> +# Download patches
> +# Explicitly depend on linux download archive so that custom tarballs get
> +# redownloaded if the configured file changes.
> +$(LINUX26_DIR)/.stamp_downloaded: $(DL_DIR)/$(LINUX26_SOURCE)
>        $(foreach patch,$(filter ftp://% http://%,$(LINUX26_PATCH)),\
>                $(call DOWNLOAD,$(dir $(patch)),$(notdir $(patch)))$(sep))
>        mkdir -p $(@D)
> I wanted to submit this to the list, but just noticed that linux is
> now using the gentargets infrastructure. To address this problem we
> can
> a. adapt gentargets, so that the generic .stamp_downloaded rule also
> depends on the downloaded archive. Is there any reason why this would
> not be good?
> b. adapt the version string in linux.mk so that a custom tarball is
> automatically picked up.


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