Linux 3.7 Kernel To Support Multiple ARM Platforms

hypnosec writes with news that the Linux 3.7 kernel will support multiple ARM-based System on Chip platforms (Git commit page), writing "Up until now there has been a separate Linux kernel build for each of the ARM platforms or SoCs, which is one of the several problems when it comes to ARM based Linux. The merging of ARM multi-platform support into Linux 3.7 will put an end to this problem, enabling the new kernel to not only target multiple platforms but also be more in line with its x86 counterpart."

Comments

Linus flaming gets job done

[amorsen]

It happened again, Linus flaming people gets stuff done.

It all started a year and a half ago with this innocent-sounding topic: [GIT PULL] omap changes for v2.6.39 merge window.

Of course it helped that most of the developers in the ARM community seemed to agree with the point Linus made. Other concerns had just taken priority.

Re:Clue wanted

[Anonymous Coward]

Those are different ARM based SoCs ("System on a chip"). The problem with the ARM platform is that ARM is not really a platform: The unifying aspect is the line of CPUs in the chip, but the SoCs come with different sets of peripherals. Even simple things like what GPIO (General Purpose IO) is connected to what LED or other function require a completely separate hardware configuration compiled into the kernel. On a PC, the kernel uses the BIOS and self-describing hardware to set everything up and choose the right drivers. No such thing exists on ARM. The kernel has to be told manually what's where. That's why you can't currently take a kernel which is compiled for one ARM SoC and use it on a different kind of ARM SoC. You're lucky if you can use the same kernel on the same ARM SoC in a different device that just happens to have everything wired up slightly differently. You may find that the GPIO that turns on the power LED on one system turns off USB power on another system. Then you need to patch the kernel or, if you want to have mainline support, register a new arc number and have yet another configuration added to the kernel. It's a fucking mess.

Re:Unified platform?

[MightyMartian]

A Device Tree description is a helluva easier to roll out than a newly compiled kernel for every device. I agree it's not ideal, but the ARM ecosystem is a bloody complicated one, and it's likely the best we can expect until that little piece of the Wild West is tamed. And maybe it never will be, as the attraction of ARM is precisely in its non-one-size-fits-all way of doing things.

If I'm looking at porting my kernel and software stack to some new ARM device, I'll take some comfort in the fact that the bulk of getting it running will be a spec file, and not having to do a kernel configure and compile. I've wasted enough hours of my life doing that sort of thing.