5 ms·

Linux is modular, you can remove the parts you don't want. Linux has multiple real-time varietals. Linux has no IP issues that I know of.

ahartmetz 9y ago
IP issue: Google doesn't have the right to give hardware vendors a pass on proprietary drivers for Linux. Ignoring the problem seems to work so far, though. That said, a stable driver API with the possibility to update the kernel without updating drivers is probably more important to Google. In the best case (and I expect a worse result than that) it means that Android phones can be updated for a long time without requiring support from the vendor. The damn vendors should just upstream the damn drivers. Drivers for embedded hardware are such a clusterfuck. You have no idea how bad it is unless you have worked in that space.
- greglindahl 9y ago
  Linux "enterprise" distributions update things for a long time without requiring support from the hardware vendor. Google's familiar with this approach, I hear that they backported x86-64 to an earlier kernel for years.
  - ahartmetz 9y ago
    In the embedded case, usually only vendors have (or used to have, who knows if they use source control) the source code. As I said, you have no idea how bad it is unless you've had to work with that crap. Maybe have a look at "Bad" in this classic. https://www.dolphin-emu.org/blog/2013/09/26/dolphin-emulator-and-opengl-drivers-hall-fameshame/?cr=de https://www.dolphin-emu.org/blog/2013/09/26/dolphin-emulator... Edit: right, you can backport fixes and features while keeping the ABI stable. That is what Google seems to be doing with Android kernels to some degree.
- swiley 9y ago
  Linux being GPLed is probably the only reason it's used so often on all these different embeded platforms. No one is sharing code on these other oses unless you have piles of money but with Linux anyone can pretty much click "y" in menuconfig and you're good to go on nearly anything. The GPL has made Linux a "Universal Kernel" of sorts.
cwyers 9y ago
And Google has done that -- for instance, they use Binder for IPC instead of dbus/kdbus on Android. But every time Google does that, they pay a price for using Linux, as they have to maintain anything in the kernel that doesn't make it upstream. The reason Google cares about this, as noted elsewhere, is that there is no stable kernel ABI for drivers, so vendors who release drivers-as-blobs, fail to release the driver source code (yes, it's a GPL violation; yes, it happens anyways) or otherwise pin their driver to a specific ABI need to release new drivers every time the kernel changes. Google would love to release Android versions independently of drivers, the way Windows works.
- EddieRingle 9y ago
  > Google would love to release Android versions independently of drivers, the way Windows works. Which they'll be able to do with Project Treble: https://android-developers.googleblog.com/2017/05/here-comes-treble-modular-base-for.html https://android-developers.googleblog.com/2017/05/here-comes...
  - c8g 9y ago
    it won't update the kernel part.
- swiley 9y ago
  If they had stuck with the APIs and ABIs literally everyone else uses they wouldn't have this problem in the first place. Most people's userspace is not tied this heavily to the kernel version because the APIs and ABIs there are fairly stable.

ahartmetz 9y ago

IP issue: Google doesn't have the right to give hardware vendors a pass on proprietary drivers for Linux. Ignoring the problem seems to work so far, though. That said, a stable driver API with the possibility to update the kernel without updating drivers is probably more important to Google. In the best case (and I expect a worse result than that) it means that Android phones can be updated for a long time without requiring support from the vendor. The damn vendors should just upstream the damn drivers. Drivers for embedded hardware are such a clusterfuck. You have no idea how bad it is unless you have worked in that space.

greglindahl 9y ago
Linux "enterprise" distributions update things for a long time without requiring support from the hardware vendor. Google's familiar with this approach, I hear that they backported x86-64 to an earlier kernel for years.
- ahartmetz 9y ago
  In the embedded case, usually only vendors have (or used to have, who knows if they use source control) the source code. As I said, you have no idea how bad it is unless you've had to work with that crap. Maybe have a look at "Bad" in this classic. https://www.dolphin-emu.org/blog/2013/09/26/dolphin-emulator-and-opengl-drivers-hall-fameshame/?cr=de https://www.dolphin-emu.org/blog/2013/09/26/dolphin-emulator... Edit: right, you can backport fixes and features while keeping the ABI stable. That is what Google seems to be doing with Android kernels to some degree.
swiley 9y ago
Linux being GPLed is probably the only reason it's used so often on all these different embeded platforms. No one is sharing code on these other oses unless you have piles of money but with Linux anyone can pretty much click "y" in menuconfig and you're good to go on nearly anything. The GPL has made Linux a "Universal Kernel" of sorts.

cwyers 9y ago

And Google has done that -- for instance, they use Binder for IPC instead of dbus/kdbus on Android. But every time Google does that, they pay a price for using Linux, as they have to maintain anything in the kernel that doesn't make it upstream. The reason Google cares about this, as noted elsewhere, is that there is no stable kernel ABI for drivers, so vendors who release drivers-as-blobs, fail to release the driver source code (yes, it's a GPL violation; yes, it happens anyways) or otherwise pin their driver to a specific ABI need to release new drivers every time the kernel changes. Google would love to release Android versions independently of drivers, the way Windows works.

EddieRingle 9y ago
> Google would love to release Android versions independently of drivers, the way Windows works. Which they'll be able to do with Project Treble: https://android-developers.googleblog.com/2017/05/here-comes-treble-modular-base-for.html https://android-developers.googleblog.com/2017/05/here-comes...
- c8g 9y ago
  it won't update the kernel part.
swiley 9y ago
If they had stuck with the APIs and ABIs literally everyone else uses they wouldn't have this problem in the first place. Most people's userspace is not tied this heavily to the kernel version because the APIs and ABIs there are fairly stable.