Hi,
I'm just getting started on this great platform and I've got some questions
about capes/overlays on which I thought perhaps someone could share their
expertise.
Most of the documentation you find online still refers to cape manager and
slots, which is slightly confusing for beginners. I did find this page [1]
and I understand (I think) that t*here is no longer a cape manager and that
u-boot does the loading of capes*.
So first questions:
- Is this assumption correct?
- I do understand the concept of the device tree and loading overlays,
but... what is the difference between *overlays*, *capes* and *virtual
capes*? I've seen all mentioned in various places, but nowhere could I find
a description of each. I've also seen "*manual overlays*" mentioned. Do
they all actually refer to the same thing?
- How can one see which capes/overlays are loaded once the system has
booted up in the new uboot overlays world?
I'm starting to look at the PRUSS and how to use them, and I'm not sure
which overlays should be loaded to enable them, or if access to them is
already enabled by default. On /boot/uEnv.txt there seem to be a couple of
options, one of which is commented out. I notice the difference in the
naming ('*-RPROC-*', vs. *-UIO-* commented out), so I'm guessing that the
RPROC PRUSS overlay is loaded and the UIO one is not.
But could someone elaborate a bit more on this?
###PRUSS OPTIONS
###pru_rproc (4.4.x-ti kernel)
uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-4-TI-00A0.dtbo
###pru_uio (4.4.x-ti & mainline/bone kernel)
#uboot_overlay_pru=/lib/firmware/AM335X-PRU-UIO-00A0.dtbo
Finally, on my /boot/uEnv.txt file I can see these lines, which I
understand are for older kernels. As a humble piece of feedback from a
newcomer, these make the file more confusing for options that no longer
apply. Would it not make sense to remove them for new images?
##Example v3.8.x
#cape_disable=capemgr.disable_partno=
#cape_enable=capemgr.enable_partno=
##Example v4.1.x
#cape_disable=bone_capemgr.disable_partno=
#cape_enable=bone_capemgr.enable_partno=
Thanks!
[1] https://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays
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