out of tree [LWN.net]

out of tree

Posted Aug 5, 2009 10:32 UTC (Wed) by farnz (guest, #17727)
In reply to: out of tree by mikov
Parent article: A tempest in a tty pot

> The thing is, and this is from direct personal experience, companies > maintaining out of tree drivers don't put their driver through the Linux > code review process; as a result, they ignore standard Linux interfaces > in favour of inventing their own. I have no opinion about this because I haven't personally experienced it, but I believe you. But why isn't this a problem in Windows?

It is a problem in Windows, too; for example, very few graphics card drivers support Windows native screen rotation in XP - you need to use a vendor utility instead. The difference is that Windows users are used to this, and don't complain as loudly about it. It's becoming less of an issue as things like USB standardize more and more device classes, and manufacturers use the standard classes, because that means that the device is Plug And Play under currently shipping Windows systems (Vista, future Windows 7 installs).

> Add to that the fact that they lose interest in maintaining their driver > at all when they've moved onto the new shiny (in the case of one vendor > I've dealt with, the driver stops being maintained as soon as they have > a new chip out, even though they're still selling the old chip), and the > fact that I don't have the time to do more than bugfix drivers that have > already been ported to new APIs, and I find myself thinking that all the > advantages you claim for out of tree drivers are disadvantages from my > perspective. Agreed, but what is your point? You are describing exactly the problems caused by a lack of stable API. Vendors do not want to maintain drivers for hardware which they no longer sell, because it is a never ending cycle of completely pointless but expensive work (from their standpoint). That would not be the case if there was a stable API.

Oops - my bad. I forgot to mention that the case in question was migrating from NT4 to XP in an embedded product. We could still buy the chips in question, but the NT4 driver didn't work in XP, even after we recompiled it against the new DDK (don't know why - I thought there was a stable API?). We ended up having to buy new ASI capture chips, and scrapping the older hardware.

> reminds me of a > subset of nVidia graphics card owners, who complain bitterly (regardless > of technical reasons) when X.org releases a new version of the X server > that isn't backwards compatible with the ancient version of the nVidia > drivers that supports their older hardware; I would like to see an open source Nvidia driver as much as the next guy, but I have to disagree with you. How did Microsoft manage to keep their graphics driver API the same from NT 3.1 to Windows XP? To think that it is a bad thing is to ignore reality.

They didn't keep the graphics driver API the same from NT 3.1 to Windows XP. Newer OSes cannot run graphics cards using older drivers, pure and simple. No different to Linux, in that respect.

And note that vendors do need to bring the Linux community on board - my employer alone buys a significant number of TV capture cards a month, on condition that they are supported under Linux. We pay a slight premium to buy Hauppauge cards because of the Linux support; other vendors are £5/card cheaper, but cost huge amounts of money in expensive developer time keeping the card going.

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out of tree

Posted Aug 5, 2009 18:05 UTC (Wed) by mikov (subscriber, #33179) [Link]

It is a problem in Windows, too; for example, very few graphics card drivers support Windows native screen rotation in XP - you need to use a vendor utility instead.

I don't want to defend Windows, but IIRC that is technically wrong. Unless I am mistaken, XP does not support native screen rotation. It was introduced in Vista.

I do agree with your general point that you can't rely on the vendors to "do the right" thing. Vendors do suck. I have seen really really horrible disgusting things working with closed source drivers. But this is an impossible battle. You can't require all developers for your OS to be perfect. People will do whatever they want to do. The best you can do is give them tools encouraging them in the right direction. Plus, hopefully GPL will shame them into better code.

Look at Google Android. They are basically doing whatever they want with the kernel and not bothering to submit anything back.

They didn't keep the graphics driver API the same from NT 3.1 to Windows XP. Newer OSes cannot run graphics cards using older drivers, pure and simple. No different to Linux, in that respect.

I am sorry but that is not quite true either. In a previous life I used to do Windows kernel development, and graphics drivers specifically. I have ported drivers from NT4 to W2K and WXP. The API remained backwards compatible and even binary compatible.

In NT4 they did a fundamental architectural change by moving the drivers into the kernel, but the source level API remained compatible with NT 3.51.

And note that vendors do need to bring the Linux community on board - my employer alone buys a significant number of TV capture cards a month, on condition that they are supported under Linux. We pay a slight premium to buy Hauppauge cards because of the Linux support; other vendors are £5/card cheaper, but cost huge amounts of money in expensive developer time keeping the card going.

I don't quite follow. Can you please clarify a bit? Why do the other cards need huge amounts of money? Also, you are saying that Hauppauge is more expensive because it has to support Linux. So, how is that a good thing?

out of tree

Posted Aug 5, 2009 18:15 UTC (Wed) by johnflux (subscriber, #58833) [Link]

> I don't quite follow. Can you please clarify a bit? Why do the other cards need huge amounts of money? Also, you are saying that Hauppauge is more expensive because it has to support Linux. So, how is that a good thing?

I think his point was that his company was willing to pay extra just for linux support. So Hauppauge was able to charge more money, and still get his custom. Whereas the companies that didn't support Linux didn't get his business.

From a business point of view, if the money that a company loses because of their lack of linux support is greater than the cost of opening the specs or writing the drivers, then the company should write Linux drivers. The poster was providing anecdotal evidence to indicate that they believe that this is the case for some (most?) companies.

On a personal note, I think companies perceive the cost of opening their drivers to be far higher than it really is.

out of tree

Posted Aug 5, 2009 18:45 UTC (Wed) by farnz (guest, #17727) [Link]

Hauppauge cards tend to work out of the box with a recent enough kernel; when they don't, Hauppauge employees are happy to help you make the cards work. Other vendors cards require developer time to make work, and attempts to get the vendor to help tend to be fruitless (they have their own out of tree driver that doesn't work well, due to reinvention of interfaces, and don't understand why you won't simply rewrite your userspace to match their driver).

Developer time is hugely expensive, as we don't have much to spare; given the choice between a small amount of extra money per card (to the vendor), or developer time, we'd rather pay. If you're a vendor, looking to expand, this is a market, and it has money to spend on you.