Update to always pull latest raspberry pi firmware from github using API

[brian-provenzano]

What was changed / proposed change

Currently reving the firmware for the raspberrypi requires manually updating the script. This PR would instead use the github api to always pull the latest firmware tarball eliminating this need.

Update

Per comment , added the ability to user select raspberry pi firmware version via an environment variable RASPBERRY_PI_FIRMWARE

• If unset, the script uses a known good version ( set as DEFAULT_GOOD_PI_VERSION in the script)
• Set to latest which instructs the script to always pull the latest version for the raspberry pi fimrware repo (e.g. export RASPBERRY_PI_FIRMWARE=latest)
• Set to a specific version which instructs the script to use that version (e.g. export RASPBERRY_PI_FIRMWARE="1.20200212")

[sgielen]

Thank you @brian-provenzano, this is nice and well-written.

Even though pulling the latest firmware is very unlikely to ever fail, considering the well-tested nature of the raspberry pi firmware, I'd still like to make this behaviour optional and to use a "known-good" firmware by default. This way, people can use the latest firmware easily if they want to, or use a known-good firmware otherwise.

Could you make this change? For example, we could add a RASPBERRY_PI_FIRMWARE environment variable, that could be:

• unset, in which case it is initialized to a known good version,
• set by the caller to some version they want, or
• set to "latest" in which case your code checks if jq is available and pulls the latest tag.

Bonus points if you could add this behaviour to the README as well. :)

Also, I have one more request: I have some instructions here on compiling kernel modules for the kernel shipped within the raspberry pi firmware, but those instructions use a hard-coded firmware version. I'd like to read the firmware version from the disk somehow when k3os is running. I think the tarball contains it, but we might not copy it to the boot. This is totally optional, and I'll merge your PR if you don't feel like adding it, but if you could take a look whether we could include that version in the image somehow, that'd be cool :)

[brian-provenzano]

Thank you @brian-provenzano, this is nice and well-written.

Even though pulling the latest firmware is very unlikely to ever fail, considering the well-tested nature of the raspberry pi firmware, I'd still like to make this behaviour optional and to use a "known-good" firmware by default. This way, people can use the latest firmware easily if they want to, or use a known-good firmware otherwise.

Could you make this change? For example, we could add a RASPBERRY_PI_FIRMWARE environment variable, that could be:

* unset, in which case it is initialized to a known good version,

* set by the caller to some version they want, or

* set to "latest" in which case your code checks if `jq` is available and pulls the latest tag.

Bonus points if you could add this behaviour to the README as well. :)

OK, I can look into this. I'll try to scrape together some time in the next week.

Also, I have one more request: I have some instructions here on compiling kernel modules for the kernel shipped within the raspberry pi firmware, but those instructions use a hard-coded firmware version. I'd like to read the firmware version from the disk somehow when k3os is running. I think the tarball contains it, but we might not copy it to the boot. This is totally optional, and I'll merge your PR if you don't feel like adding it, but if you could take a look whether we could include that version in the image somehow, that'd be cool :)

I might save this one for another time if that is OK. Probably better if it is a change of its own anyway. :)

[brian-provenzano]

Thank you @brian-provenzano, this is nice and well-written.

Even though pulling the latest firmware is very unlikely to ever fail, considering the well-tested nature of the raspberry pi firmware, I'd still like to make this behaviour optional and to use a "known-good" firmware by default. This way, people can use the latest firmware easily if they want to, or use a known-good firmware otherwise.

Could you make this change? For example, we could add a RASPBERRY_PI_FIRMWARE environment variable, that could be:

* unset, in which case it is initialized to a known good version,

* set by the caller to some version they want, or

* set to "latest" in which case your code checks if `jq` is available and pulls the latest tag.

Bonus points if you could add this behaviour to the README as well. :)

Made the above change and also updated the README to reflect the new feature.
I'm no the greatest bash scripter, so let me know if this works :)

[sgielen]

Thanks a lot @brian-provenzano !