linux-firmware-rpidistro: Guard the recipe under a license flag

We do this as a result of an upstream issue[1].

Some of the firmware blobs are provided under the 'Synapse' license
including a clause that can (at least theoretically) be used as a
'killswitch'. To make sure users are aware of this, we guard this
behind a license flag.

Users of this recipe will need to add to their configuration:

    LICENSE_FLAGS_ACCEPTED = "synaptics-killswitch"

[1] https://github.com/RPi-Distro/firmware-nonfree/issues/29

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

docs/index.rst

@@ -15,6 +15,7 @@ Contents:
    layer-contents
    extra-build-config
    extra-apps
+   ipcompliance
    contributing
 
 Indices and tables

docs/ipcompliance.md

@@ -0,0 +1,23 @@
+# IP Compliance
+
+## linux-firmware-rpidistro
+
+By default, some of the machine configurations recommend packages for the
+WiFi/BT firmware, provided by
+[linux-firmware-rpidistro](https://github.com/RPi-Distro/firmware-nonfree).
+This package includes some firmware blobs under the `Synaptics` license which
+could carry a legal risk: one of the clauses can be (at least theoretically)
+used as a `killswitch`. This was
+[reported](https://github.com/RPi-Distro/firmware-nonfree/issues/29) in the
+upstream repository.
+
+You can find the full license text body in the content of the above mentioned
+package.
+
+Due to the above, the build system will only allow this recipe to be built if
+the user acknowledges this risk by adding the following configuration:
+
+    LICENSE_FLAGS_ACCEPTED = "synaptics-killswitch"
+
+You can provide this configuration as part of your `local.conf`, `distro.conf`,
+etc.

recipes-kernel/linux-firmware-rpidistro/linux-firmware-rpidistro_git.bb

@@ -13,6 +13,7 @@ LIC_FILES_CHKSUM = "\
 # license files will be copied from the fetched source.
 NO_GENERIC_LICENSE[binary-redist-Cypress-rpidistro] = "debian/config/brcm80211/copyright"
 NO_GENERIC_LICENSE[Synaptics-rpidistro] = "debian/config/brcm80211/copyright"
+LICENSE_FLAGS = "synaptics-killswitch"
 
 SRC_URI = "git://github.com/RPi-Distro/firmware-nonfree;branch=bullseye;protocol=https"
 SRCREV = "541e5a05d152e7e6f0d9be45622e4a3741e51c02"