[personal profile] mjg59
ACPI is a complicated specification - the latest version is 980 pages long. But that's because it's trying to define something complicated: an entire interface for abstracting away hardware details and making it easier for an unmodified OS to boot diverse platforms.

Inevitably, though, it can't define the full behaviour of an ACPI system. It doesn't explicitly state what should happen if you violate the spec, for instance. Obviously, in a just and fair world, no systems would violate the spec. But in the grim meathook future that we actually inhabit, systems do. We lack the technology to go back in time and retroactively prevent this, and so we're forced to deal with making these systems work.

This ends up being a pain in the neck in the x86 world, but it could be much worse. Way back in 2008 I wrote something about why the Linux kernel reports itself to firmware as "Windows" but refuses to identify itself as Linux. The short version is that "Linux" doesn't actually identify the behaviour of the kernel in a meaningful way. "Linux" doesn't tell you whether the kernel can deal with buffers being passed when the spec says it should be a package. "Linux" doesn't tell you whether the OS knows how to deal with an HPET. "Linux" doesn't tell you whether the OS can reinitialise graphics hardware.

Back then I was writing from the perspective of the firmware changing its behaviour in response to the OS, but it turns out that it's also relevant from the perspective of the OS changing its behaviour in response to the firmware. Windows 8 handles backlights differently to older versions. Firmware that's intended to support Windows 8 may expect this behaviour. If the OS tells the firmware that it's compatible with Windows 8, the OS has to behave compatibly with Windows 8.

In essence, if the firmware asks for Windows 8 support and the OS says yes, the OS is forming a contract with the firmware that it will behave in a specific way. If Windows 8 allows certain spec violations, the OS must permit those violations. If Windows 8 makes certain ACPI calls in a certain order, the OS must make those calls in the same order. Any firmware bug that is triggered by the OS not behaving identically to Windows 8 must be dealt with by modifying the OS to behave like Windows 8.

This sounds horrifying, but it's actually important. The existence of well-defined[1] OS behaviours means that the industry has something to target. Vendors test their hardware against Windows, and because Windows has consistent behaviour within a version[2] the vendors know that their machines won't suddenly stop working after an update. Linux benefits from this because we know that we can make hardware work as long as we're compatible with the Windows behaviour.

That's fine for x86. But remember when I said it could be worse? What if there were a platform that Microsoft weren't targeting? A platform where Linux was the dominant OS? A platform where vendors all test their hardware against Linux and expect it to have a consistent ACPI implementation?

Our even grimmer meathook future welcomes ARM to the ACPI world.

Software development is hard, and firmware development is software development with worse compilers. Firmware is inevitably going to rely on undefined behaviour. It's going to make assumptions about ordering. It's going to mishandle some cases. And it's the operating system's job to handle that. On x86 we know that systems are tested against Windows, and so we simply implement that behaviour. On ARM, we don't have that convenient reference. We are the reference. And that means that systems will end up accidentally depending on Linux-specific behaviour. Which means that if we ever change that behaviour, those systems will break.

So far we've resisted calls for Linux to provide a contract to the firmware in the way that Windows does, simply because there's been no need to - we can just implement the same contract as Windows. How are we going to manage this on ARM? The worst case scenario is that a system is tested against, say, Linux 3.19 and works fine. We make a change in 3.21 that breaks this system, but nobody notices at the time. Another system is tested against 3.21 and works fine. A few months later somebody finally notices that 3.21 broke their system and the change gets reverted, but oh no! Reverting it breaks the other system. What do we do now? The systems aren't telling us which behaviour they expect, so we're left with the prospect of adding machine-specific quirks. This isn't scalable.

Supporting ACPI on ARM means developing a sense of discipline around ACPI development that we simply haven't had so far. If we want to avoid breaking systems we have two options:

1) Commit to never modifying the ACPI behaviour of Linux.
2) Exposing an interface that indicates which well-defined ACPI behaviour a specific kernel implements, and bumping that whenever an incompatible change is made. Backward compatibility paths will be required if firmware only supports an older interface.

(1) is unlikely to be practical, but (2) isn't a great deal easier. Somebody is going to need to take responsibility for tracking ACPI behaviour and incrementing the exported interface whenever it changes, and we need to know who that's going to be before any of these systems start shipping. The alternative is a sea of ARM devices that only run specific kernel versions, which is exactly the scenario that ACPI was supposed to be fixing.

[1] Defined by implementation, not defined by specification
[2] Windows may change behaviour between versions, but always adds a new _OSI string when it does so. It can then modify its behaviour depending on whether the firmware knows about later versions of Windows.
erika: (st aos: your mom (jtk))
[personal profile] erika
I can feel the rumble of the trains as I wait outside.

Robot of Sherwood/Listen

Sep. 15th, 2014 09:38 am
[personal profile] yendi
So after two awful episodes, we get two really good ones. I'm not totally shocked about "Listen," since standalone horror tends to be a good genre for the Doctor and for Moffat, but I'm really surprised at the first one.

Putting everything beneath one tag for simplicity, since it's hard to separate out speculation.

Read more... )

Rereading The President’s Daughter

Sep. 14th, 2014 08:41 pm
grrlpup: (rose)
[personal profile] grrlpup

I spent quite a lot of this weekend rereading Ellen Emerson White’s The President’s Daughter, the updated 2008 edition that has email and cell phones that are curiously underused. (The original, which I’ve never seen, was published in 1984. Hmm, liberal-fantasy presidency 15 years before West Wing?)

I took it with me to get the car’s oil changed. I read it on the porch with many glasses of ice water. (I read it in the bathroom.) I finished it tonight in the back yard, while Sang worked on a story and hummingbirds navigated the lilac boughs overhead. (I speculated that the small-even-for-a-hummingbird male might be this year’s nestling. “Is that why we keep having to duck?” Sang said. “Do they need a tiny DRIVER IN TRAINING plaque?”)

Oh, thorny teenage girls named Meg! Oh, large number of commas, and pets who get patted instead of petted. I love how friends and family play in this book: deadpan verbal jousting, with one taking up the other’s lead.

I first read this in 2009. (My note then: “Nice to read a book about a rich girl that’s not all glitz and shopping.”) But it’s this time around that so much of it reminds me of President Obama’s inauguration. Meg and her family spend a lot of time deciding what to wear–remember how it was a big deal that Malia and Sasha wore J Crew coats to the inauguration? And the first time Meg and her brothers tour the White House reminded me of the Obama girls talking about the Bush twins showing them around, and how nice they were.

But the Vaughns don’t get a new puppy.

It does make me wonder how this book would read to me if we’d had a Hillary Clinton presidency instead. More echoes? Maybe not, though, as Chelsea wasn’t a kid anymore in 2008.

I hadn’t really planned on reading the whole series again, necessarily, but now I know I’m going to.

This post also appears at read write run repeat. Comments read and welcomed in either place!

alixtii: Riley and Venom, from Season 4. (Riley/Venom 2)
[personal profile] alixtii


Title: Tiens, Voilà Dix Sous, pour la Salle-de-Bains
Author: [personal profile] alixtii
Fandom: Buffy the Vampire Slayer
Pairing: Buffy/Darla
Summary: Taking care of one another is what this world is about.
A/N: Set in an AU season 6 where Darla was chipped instead of Spike. Spoilers for everything up to "Once More, With Feeling," say. Title from T.S. Eliot's poem "Dans le Restaurant."

Format: MP3
Length: 0:23:40
Size: 21.9 MB

Links
Original text at AO3.
Download or stream from Google.
Temporary download from Sendspace.
alixtii: (Lockers)
[personal profile] alixtii
So, during the 20 minutes before I left for church on Sunday, I may have committed this [community profile] fic_corner treat...

To Dream a Dream (469 words) by [archiveofourown.org profile] Alixtii
Fandom: Alice In Wonderland - Lewis Carroll, Alice's Adventures in Wonderland & Related Fandoms
Characters: Alice (Alice in Wonderland), Alice Liddell, Original Female Character

Summary: The dreams haven't stopped for Alice Liddell, but she has learned to control them.

( To Dream a Dream )

[personal profile] yendi
Everyone (rightly) assails Electronic Arts for their Free-to-Play model and how it undercut Dungeon Keeper, Madden, Ultima, and other franchises on mobile devices.

But everyone also throws Plants vs Zombies 2 into that listing.

And that's fucking wrong.

PVZ 2 was a solid game on release, and has gotten better and better with each update. There are no timers (the bane of FTP games), and the game is entirely playable and winnable without paying a cent. The stuff you can buy are new plants and coins that allow power-ups. Or, to put it another way, you can basically pay for the equivalent of cheat codes.

That's a fine model by me.

There are more levels in the game now than in the original paid game. They've added Vasebreaker, the second-best of the minigames, and I hope they'll add "I, Zombie," which was the best one. But as it stands, it's a damned fine game, and really deserves not to be lumped in with the rest of those creative failures.
[personal profile] yendi
The headline was great news. Comedian Michael Che will be added as a new anchor for Weekend Update. Che was wonderful on The Daily Show, and given how utterly awful Colin Jost was, replacing him (and with the first ever person of color behind the desk) is a great move.

But no.

Che is replacing Cecily Strong. Who was fucking wonderful.

Pull quote from the article:

"Mr. Michaels said that Mr. Che, who has had a career as a stand-up comedian in New York, formed a close relationship last year in the writers’ room with Mr. Jost, one of the show’s two head writers." So after a year in which the show was hamstrung by the brotastic idiocy of making the cast even more male than ever, they're going with two men behind the desk. And basically kowtowing to Jost because he's the head writer, even though he's been awkward and awful at telling jokes in front of the camera.

The argument about Strong wanting to be in more skits sounds great until you remember that she was in as many skits as any of the female cast members last season (more than most) while doing hosting duties. This is all about Jost, folks. Yes, he's a talented writer, but that's not a reason to make this decision.

Look. There are only a handful of really strong performers at the show right now, and the majority of them are women (only Bobby Moynahan and Jay Pharaoh stand out amongst the males, while the women, now that Noël Wells is gone, are as strong a group as they've ever had).

On the plus side, we might see the return of The Girl You Wish You Had Never Started a Conversation With. As silver linings go, it's a small one, but I'll take what I can get.

The Interrogation of Ashala Wolf

Sep. 9th, 2014 09:28 pm
grrlpup: (rose)
[personal profile] grrlpup

I’ve been doing a little cleaning tonight while Sang is at work teaching. The method I’m using is, “Step through the front door and see what first strikes you as messy.” Which turned out to be the stacks of books and papers and mail on the barstools. And one of the books was Ambelin Kwaymullina’s The Interrogation of Ashala Wolf, which I want to tell you about before I put it back on the shelf. Ambelin Kwaymullina is an Indigenous author from Western Australia, and this book is the first in her four-book series of YA dystopian novels.

YA dystopia can go either way for me. Sometimes I open a book and see all those capitalized general nouns (the Illegals, the Citizens, the Balance) and just can’t get into it. But this one got me past that with a badass protagonist and her crew, kids with superpowers basically. Ashala’s tagline: “I walk among my enemies. But I carry my friends with me.” And the friends are varied and imperfect.

But what really set it apart for me is the structure of flashbacks and reveals. The flashbacks are in a different typeface, and flipping through, it looks like maybe a third of the book is flashback. I would come to a flashback section and kind of set my teeth to get through it. You know what I mean? I was willing to do it to fill in the information I needed, but I was anticipating an extra effort and less momentum because we were out of the main storyline. But every time, I would get completely sucked in and wasn’t on that secondary track in my head at all, plus I was reinterpreting what I’d already read.

I don’t follow the genre that closely, but it kinda seems like this one should be getting more attention. It’s the first of a four-book series, but didn’t end on a cliffhanger. The second book has been published in Australia. I hope Candlewick does the US edition of all four.

This post also appears at read write run repeat. Comments read and welcomed in either place!

alixtii: Riley and Venom, from the end of season 3. (Riley/Venom)
[personal profile] alixtii
Here's the story I wrote for [community profile] fic_corner:

Punk and Circumstance (3607 words) by [archiveofourown.org profile] Alixtii
Fandom: Nick and Norah's Infinite Playlist - Rachel Cohn & David Levithan
Relationship: Nick O'Leary/Norah Silverberg
Characters: Nick O'Leary, Norah Silverberg, Caroline (Nick & Norah's Infinite Playlist), Tris (Nick & Norah's Infinite Playlist), Ira Silverberg

Summary: Nick attends the Sacred Heart graduation ceremonies--and the surprisingly intimate afterparty.


( Punk and Circumstance )


Free iOS Monday

Sep. 8th, 2014 05:57 pm
[personal profile] yendi
1. Gorodki has gone free briefly a few times recently, and is free now. It's a fun little puzzle game in which you throw a wooden bat at in interlocking toy to knock the toy pieces off a table. It's strange, but rather fun.

2. Wonderputt is the most surreal mini golf game I've seen. I only just grabbed it last night, so haven't played it a lot, but the animations remind me a lot of the wonderful Grow games.

3. The IGN Free Game of the Month is Hitman Go (linked because you have to go through IGN to get it for free), which you MUST grab if you have a device that can run it. It's a turn-based stealth strategy game, nothing like its PS3/Xbox cousins. The aesthetic alone, in which the characters are all cardboard board game pieces, is wonderful, and the puzzles can get incredibly difficult. Also note that this one is international, and covers folks in the UK and Canada (and a bunch of other countries) too.

4. Angry Birds Stella is out. I'm not sure anyone who likes Angry Birds can miss the news about a new game, but in case you missed it, here you go. I've only played a few levels, but it is, not surprisingly, more Angry Birds-style gameplay. I'm generally fine with that, and am fine with it here. There are a few FTP hooks, but nothing big that I've seen (it's comparable to Angry Birds Star Wars 2, offering chances to buy power-ups and the like).

Fic Corner, Yuletide, and Me

Sep. 5th, 2014 06:31 pm
alixtii: Peter and Valentine Wiggin, from the Ender's Game comic book. (Ender's Game)
[personal profile] alixtii
I left a comment on the Yuletide fandom promotion post advertising Rebecca of Sunnybrook Farm. I'd also like to promote the other two fandoms I plan on nominating, The Illuminatus! Trilogy and That Guy With the Glasses, but I really don't have the least clue how to go about it. They're not easy fandoms to explain, exactly.

(All three fandoms are ones I made requests for last year, so my Dear Yulewriter Letter ought to be pretty easy to write this year. And whatever won't get written will qualify for the Some Day My Fic Will Come Challenge.)

In the meantime, I'm making last-minute edits to my [community profile] fic_corner story. Stories are supposed to go live tomorrow, but there's still one participant who hasn't yet gotten a fic written for them, so if you can write something for Dreamdark series - Laini Taylor, Snow Eyes series - Stephanie A. Smith, Toaru Kagaku no Railgun | A Certain Scientific Railgun, or Ultra Maniac then go here; if you can write for Dark Is Rising Sequence – Susan Cooper then go here.

Looking at the fandoms, it looks like the [community profile] fic_corner story written for me will be either Ender's Game or The A.I. Gang both of which would be awesome.

I had hoped to have completely finished Where the Heart Is by the time Yuletide assignments went out, but that's looking unlikely at this point. Although the antepenultimate chapter is mostly finished at this point, so hopefully I will get a chance to post it at least sometime in the next few weeks. I really do love those wacky incestuous kids. The sequel Where They Have to Take You In and prequel "One's Birthplace, Ratified by Memory" mostly just exist in my brain at this point. As does quite a bit of MCU fic, including a bunch of genderswap fic (Stephanie/Coulson, Toni/Natasha, Clint/girl!Thor) as well as sequels to The Caged Birds (including Coulson/Darcy, Tony/Pepper/Jane, and Bruce/Natasha fics).

Pop Music, Fuck yeah!

Sep. 5th, 2014 09:21 am
[personal profile] yendi
So, the choices for "Song of the Summer 2014" are:

1. A ridiculously catchy song by an average-sized or below average woman that seems to be about body acceptance until it calls out "skinny bitches." (See also this deconstruction, worth it alone for the term "fatcceptable movement."

2. A ridiculously catchy song by a woman even skinnier than the first woman that's also seemingly about body acceptance, until it, too, calls out "skinny bitches."

3. A hideously uncatchy song by a white guy appropriating reggae music poorly in which the narrator and a woman's father argue about a woman with no agency, and which has been described as the aural equivalent of a man listening to reggae for the first time in his racecar bed, slowly fucking the hole in a Kidz Bop CD.

4. A rap song with the screetchist chorus ever by a white Australian girl with a history of racism and homophobia.

5. Sam Smith's "Stay With Me."
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