[Buildroot] [PATCH 1/1] package/rpi-firmware: add overlays/README

[Tim Gover]

On Mon, 31 Oct 2022 at 12:39, Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
>
> Tim, All,
>
> On 2022-10-31 11:46 +0000, Tim Gover spake thusly:
> > If a custom os_prefix directory is specified then the Raspberry Pi
> > firmware probes for the README file in overlays directory.
> >
> > Since the README file is small let's include it, otherwise,
>
> 197KiB is _not_ small. In fact, the README is bigger than every dtbo,
> and accounts for ~25% of the size of all dtbo combined.

Good point. Would you be happy with simply creating an empty or small
README file (a note indicating the purpose of the file) ?

> > the firmware won't recognize the overlays directory if the user
> > later moves it to an os_prefix specific sub-directory.
>
> What is the goal here, in the context of Buildroot, where we only
> install one set of overlays?
>
> If a user moved the overlays, they already have a script that does that,
> so they should also ensure that script properly prepares config.txt to
> specify the proper os_prefix, and so it is just a matter of adding a
> 'touch' on the README in the same script.

It's fairly common for non-expert users to modify the output of a
buildroot image
without re-building the image themselves. Adding a README file reduces
the risk of them being tripped up by this difference in behaviour.

>
> Regards,
> Yann E. MORIN.
>
> > From
> > https://www.raspberrypi.com/documentation/computers/config_txt.html#overlay_prefix
> >
> > Unless ${os_prefix}${overlay_prefix}README exists, overlays are shared
> > with the main OS (i.e. os_prefix is ignored).
> >
> > Signed-off-by: Tim Gover <tim.gover at raspberrypi.com>
> > ---
> >  package/rpi-firmware/rpi-firmware.mk | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/package/rpi-firmware/rpi-firmware.mk b/package/rpi-firmware/rpi-firmware.mk
> > index d4d1d07b3f..908d7def6a 100644
> > --- a/package/rpi-firmware/rpi-firmware.mk
> > +++ b/package/rpi-firmware/rpi-firmware.mk
> > @@ -48,6 +48,7 @@ define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
> >       $(foreach ovldtb,$(wildcard $(@D)/boot/overlays/*.dtbo), \
> >               $(INSTALL) -D -m 0644 $(ovldtb) $(BINARIES_DIR)/rpi-firmware/overlays/$(notdir $(ovldtb))
> >       )
> > +     $(INSTALL) -D -m 0644 $(@D)/boot/overlays/README $(BINARIES_DIR)/rpi-firmware/overlays/
> >       $(INSTALL) -D -m 0644 $(@D)/boot/overlays/overlay_map.dtb $(BINARIES_DIR)/rpi-firmware/overlays/
> >  endef
> >  else
> > --
> > 2.25.1
> >
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>
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