Andrew Savchenko posted on Tue, 20 Jan 2015 23:59:23 +0300 as excerpted: > On Tue, 20 Jan 2015 12:17:35 -0800 Christopher Head wrote: >> On January 20, 2015 12:47:03 AM PST, Alexis Ballier >> <aball...@gentoo.org> wrote: >> >So, you're telling me that if you have a list of 90 cpu extensions, >> >you will from time to time open that list to see if there is a 91st >> >one added ? I think most people won't even notice, at best they'll >> >look for the changelog. >> >> No, actually, I’m advocating the exact opposite. I’m saying that, as >> long as the list file is kept up to date, then I will look at those 90 >> flags when I first install and never again. If a 91st flag appears some >> day, then as long as the file was maintained as I described in an >> earlier message (i.e. flags are added as soon as manufacturers announce >> features), I already know I can reliably ignore the new flag. After >> all, >> if the flag didn’t exist when I installed the system, then my CPU must >> necessarily not have that feature—unless CPUs are in the habit of >> sprouting new instructions after you buy them! > > Not exactly. CPUs are not in a habit, but software is. Some brand new > instuction set may be supported in (any of) packages with some delay. > Thus it is possible that instruction set supported by your CPU will > appear in the list of cpu flags after your ininial install.
PMFJI... chead's idea is (I believe) simply to have the description file updated with all current hardware feature flags as soon as they are known (he said announced, but sometimes they change between announcement and actually appearing in hardware, so "known", as in "known to actually appear in hardware", would seem to be better). That way, no matter what the software supported at the time and what flags were thus actually used in packages, when someone first installs gentoo on a new machine, or when they first upgrade their CPU to something with new features, they can run the script and update their use_expand to match their hardware _ONCE_, without worrying about whether or when a package with support for it might appear. If no package with that support ever appears, no harm done, that entry in the use_expand is simply never used. OTOH when some package /does/ get support for new hardware instructions and adds the appropriate flag, it'll appear in portage's output, but because the use_expand was already set when gentoo was installed or the cpu upgraded, the user won't have to worry about needing to look it up and decide whether to set it, again, it'll already be done, back when the _hardware_ changed, _not_ sometime later, when the _software_ changed to support the new hardware. Of course if the user upgrades hardware after a package supports a feature, they'll have to upgrade their use_expand setting appropriately or miss support for the new instructions, but that's always the case. Just if handled as chead suggests, it'd be the case ONLY when the hardware is updated, instead of every time a package upgrades its own support. Correct, chead? Does that make things clearer, aballier and bircoph? =:^) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
