Messages in this thread | | | Date | Thu, 3 Jun 1999 12:23:30 -0400 | Subject | Re: 2.3 wish: integrate pcmcia into mainstream kernel | From | tytso@mit ... |
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A couple of observations here. First of all, I'm told that Linus has a Sony Vaio laptop (one of the SLimtops, which I have as well), and yes, that *does* have the BIOS initializing the CD-ROM. I suspect it only works for the laptop which is specially made for that laptop, but that's one of the uglinesses.
Note that one of the reasons why this can be done is precisely to support booting off of El Torito CD-ROM's. If you're going to do this, you really do need to have the BIOS initialize the card for you.
So I think the main change which the PCMCIA drivers need to make is one where they can notice if the CD-ROM was plugged in during the initial power-on (and so was initialized by the BIOS), and leave well enough alone in that case. That's really the only change that needs to be made; I don't think there is a requirement to solve this particular problem that all of the PCMCIA support be moved into the kernel.
Secondly, there are still a number of very good reasons why the PCMCIA support should remain separate. Hardware manufacturers in this space are like hardware manufacturers of video cards. They make changes and tweaks to the hardware frequently. In fact, sometimes it feels like it's about roughly the same change frequency as new Linux development kernels come out. :-)
By having the PCMCIA support be done outside of kernel space, it means that David can release new PCMCIA drivers much more frequently without trying to get changes into the stable kernel series, *OR* forcing users to use a development kernel just so their devices are supported. Even if the necessary work is done to allow the first option to work, it (a) would require a number of additional stable releases, with the temptation of putting other destablizing new features into the stable kernel reelase, and (b) it's more work to maintain two branches of device drivers, one in the stable and one in the development kernel.
There is also, as David mentioned, the additional difficulty of keeping the user space and kernel space drivers in sync if they are distributed separately. As the modultils packages have shown, this isn't impossible, but it does add to the support burden.
So before we overreact and assume that we have to put PCMCIA support into the kernel, I think we need to be a little bit more careful. There will certainly be some cases --- for example, if you need your boot device be a PCMCIA device while you are bootstrapping a new port, but in general, I think our existing implementations have a number of advantages to recommend it, and we need to be careful that we keep those advantages when going to a new device architecture.
- Ted
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