snagflash: Reduce (or at least document) dependency to OEM commands being available when using fastboot

[JSydll]

Disclaimer: I'm by no means knowledgeable in the FastBoot protocol or the requirements for a generic solution when using it for flashing eMMCs.

When attempting to use snagflash to deploy software on an i.MX8MP SoC, I stumbled across the implicit requirement of the fastboot-uboot protocol to have a u-boot with at least the oem run command supported. When looking at the in-code documentation, I can't see much of a difference to the ucmd command - yet, the former is far less often supported by custom built u-boot, while the latter usually comes with it.

So is it technically possible to replace the usage of oem run by ucmd? If not, I'd vote for having it clearly documented, that the flash command of the fastboot-uboot protocol is essentially rendered useless if the command is not available. And, well, flash is maybe the primary use case of snagflash...

Of course, I can replicate the behavior by using standard fastboot commands, but I really appreciate the convenience logic that fastboot-uboot attempts to add.

So what do you think?

[rgantois]

Hi, I agree, in fact this has been on the back burner for some time now.

Ideally, I'd like to autodetect whether oem_run and/or ucmd are available at runtime and log a clear message to the user if it's not the case.

And documenting it is definitely important as well, it's already done in the snagfactory docs but not yet in the snagflash docs.

Thanks for the feedback!

[JSydll]

Thanks for the fast reply! I like the idea to ask the device about it's capabilities and choose the command function accordingly. As I'll probably experiment with this a bit, I see if time permits me to create a proposal.