I’ve been told by several sources (but not by Google directly, heh) that from Christmas onwards the “Designed for ChromeBook” sticker requires hardware vendors to use fwupd rather than random non-free binaries. This does make a lot of sense for Google, as all the firmware flash tools I’ve seen the source for are often decades old, contain layer-on-layers of abstractions, have dubious input sanitisation and are quite horrible to use. Many are setuid, which doesn’t make me sleep well at night, and I suspect the security team at Google also. Most vendor binaries are built for the specific ODM hardware device, and all of them but one doesn’t use any kind of source control or formal review process.
The requirement from Google has caused mild panic among silicon suppliers and ODMs, as they’re having to actually interact with an open source upstream project and a slightly grumpy maintainer that wants to know lots of details about hardware that doesn’t implement one of the dozens of existing protocols that fwupd supports. These are companies that have never had to deal with working with “outside” people to develop software, and it probably comes as quite a shock to the system. To avoid repeating myself these are my basic rules when adding support for a device with a custom protocol in fwupd:
- I can give you advice on how to write the plugin if you give me the specifications without signing an NDA, and/or the existing code under a LGPLv2+ license. From experience, we’ll probably not end up using any of your old code in fwupd but the error defines and function names might be similar, and I don’t anyone to get “tainted” from looking at non-free code, so it’s safest all round if we have some reference code marked with the right license that actually compiles on Fedora 31. Yes, I know asking the legal team about releasing previously-nonfree code with a GPLish licence is difficult.
- If you are running Linux, and want our help to debug or test your new plugin, you need to be running Fedora 30 or 31. If you run Ubuntu you’ll need to use the snap version of fwupd, and I can’t help you with random Ubuntu questions or interactions between the snap version and the distro version. I know your customer might be running Debian Stable or Ubuntu LTS, but that’s not what I’m paid to support. If you do use Fedora 29+ or RHEL 7+ you can also use the nice COPR I provide with git snapshots of master.
- Please reflect the topology of your device. If writes have to go through another interface, passthru or IC, please give us access to documentation about that device too. I’m fed up having to reverse engineer protocols from looking at the “wrong side” of the client source code. If the passthru is implemented by different vendor, they’ll need to work on the same terms as this.
- If you want to design and write all of the plugin yourself, that’s awesome, but please follow the existing style and don’t try to wrap your existing code base with the fwupd plugin API. If your device has three logical children with different version numbers or firmware formats, we want to see three devices in fwupdmgr. If you want to restrict the child devices to a parent vendor, that’s fine, we now support that in fwupd and on the LVFS. If you’re adding custom InstanceIDs, these have to be documented in the
- If you’re using an nonstandard firmware format (as in, not DFU, Intel HEX or Motorola SREC) then you’ll need to write a firmware parser that’s going to be valgrind’ed and fuzzed. We will need all the header/footer documentation so we can verify the parser and add some small redistributable fuzz targets. If the blob is being passed to the hardware without parsing, you still might need to know the format of the header so that the plugin can do a sanity check that the firmware is suitable for the hardware, and that any internal CRC is actually correct. All the firmware parsers have to be paranoid and written defensively, because it’s me that looks bad on LWN if CVEs get issued.
- If you want me to help with the plugin, I’m probably going to ask for test hardware, and two different versions of the firmware that can actually be flashed to the hardware you sent. A bare PCB is fine, but if you send me something please let me know so I can give you my personal address rather than have to collect it from a Red Hat office. If you send me hardware, ensure you also include a power supply that’s going to work in the UK, e.g. 240V. If you want it back, you’ll also need to provide me with UPS/DHL collection sticker.
- You do need to think how to present your device version number. e.g. is
0x12345678meant to be presented as “
12.34.5678” or “
188.8.131.52” – the LVFS really cares if this is correct, and users want to see the “same” version numbers as on the OEM web-page.
- You also need to know if the device is fully functional during the update, or if it operates in a degraded or bootloader mode. We also need to know what happens if flashing fails, e.g. is the device a brick, or is there some kind of A/B partition that makes a flash failure harmless? If the device is a brick, how can it be recovered without an RMA?
- After the update is complete fwupd need to “restart” the device so that the new firmware version can be verified, so there needs to be some kind of command the device understands – we can ask the user to reboot or re-plug the device if this is the only way to do this, although in 2019 we can really do better than that.
- If you’re sharing a huge LGPLv2+ lump of code, we need access to someone who actually understands it, preferably the person that wrote it in the first place. Typically the code is uncommented and a recipe for a headache so being able to ask a human questions is invaluable. For this, either IRC, email or even just communicating via a shared Google doc (more common than you would believe…) is fine. I can’t discuss this stuff on Telegram, Hangouts or WhatsApp, sorry.
- Once a plugin exists in fwupd and is upstream, we will expect pull requests to add either more VID/PIDs,
#defines or to add variations to the protocol for new versions of the hardware. I’m going to be grumpy if I just get sent a random email with demands about backporting all the VID/PIDs to Debian stable. I have zero control on when Debian backports anything, and very little influence on when Ubuntu does a SRU. I have a lot of influence on when various Fedora releases get a new fwupd, and when RHEL gets backports for new hardware support.
Now, if all this makes me sound like a grumpy upstream maintainer then I apologize. I’m currently working with about half a dozen silicon suppliers who all failed some or all of the above bullets. I’m multiplexing myself with about a dozen companies right now, and supporting fwupd isn’t actually my entire job at Red Hat. I’m certainly not going to agree to “signing off a timetable” for each vendor as none of the vendors actually pay me to do anything…
Given interest in fwupd has exploded in the last year or so, I wanted to post something like this rather than have a 10-email back and forth about my expectations with each vendor. Some OEMs and even ODMs are now hiring developers with Linux experience, and I’m happy to work with them as fwupd becomes more important. I’ve already helped quite a few developers at random vendors get up to speed with fwupd and would be happy to help more. As the importance of fwupd and the LVFS grows more and more, vendors will need to hire developers who can build, extend and support their hardware. As fwupd grows, I’ll be asking vendors to do more of the work, as “get upstream to do it” doesn’t scale.