[Public] > On Mon, Mar 21, 2022 at 11:57 PM Damien Le Moal > <damien.lemoal@xxxxxxxxxxxxxxxxxx> wrote: > > > > * Rename ahci_board_mobile to board_ahci_low_power to be more > descriptive > > of the feature as that is also used on PC and server AHCI adapters, > > from Mario. > > > > Mario Limonciello (3): > > ata: ahci: Rename board_ahci_mobile > > ata: ahci: Rename `AHCI_HFLAG_IS_MOBILE` > > ata: ahci: Rename CONFIG_SATA_LPM_MOBILE_POLICY configuration item > > So I've pulled this, but it's worth noting that particularly renaming > that CONFIG option was probably not a good idea. > > Why? > > Because it means that people silently lose their old values. And it has that > > range 0 4 > default 0 > > with 4 being explicitly marked as very dangerous - but at least Fedora > seems to actually have a default of 3 in their kernels: > > /boot/config-5.16.13-200.fc35.x86_64: > CONFIG_SATA_MOBILE_LPM_POLICY=3 > > so that "default 0" may actually not be the right one. > > Now, we're at the point where few enough people likely care about ATA, > but the corollary to that is also that these kinds of changes can > cause user pain that then developers have *no* idea about. > Particularly when the pain ends up being caused by some subtle default > config option silently changing that nobody even thought about. > > Now, that "default 0" is probably the only safe default - and I don't > dispute that part. But I also suspect that Fedora chose that value '3' > because it probably makes a noticeable power use difference on at > least some platforms. > > I don't know. But I doubt really *anybody* knows, so renaming them and > silently likely changing config options for some less-than-critical > reason is just not a great idea. > > Linus Thanks for pointing out the subtlety of renaming a configuration option hides problems because people don't see the new config option and pick the default. I wouldn't call this configuration option rename critical, so if you chose to revert it I would understand. However I think you raise a good point that if distros are picking different "default" values and keeping them there a long time that the value in the upstream kernel is probably not right anymore. A while back that default made sense because all the power saving stuff was risky at the time. It's pretty well baked now. So maybe a logical thing is to keep this change and send a follow up that also changes the default to 3? If you're supportive of that I'll send something to Damien to do that.
