Messages in this thread |  | | Date | Tue, 1 Jun 1999 15:30:41 -0700 | | From | David Hinds <> | | Subject | Re: 2.3 wish: integrate pcmcia into mainstream kernel |
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Linus Torvalds wrote: >> Pavel Machek <pavel@bug.ucw.cz> wrote: >> >> `subj` is my 2.3 wish. Having pcmcia support outside of standard >> kernel makes pcmcia drivers second-class citizens, which only work >> sometimes.
As an aside, I'd question the assertion that having PCMCIA outside the kernel causes it to "only work sometimes". I'm not aware of any major PCMCIA problems that have been caused by kernel version skew, and all such minor problems have been quickly fixed. I don't think PCMCIA has had more such problems than other types of drivers that *are* in the kernel: when there have been major changes in kernel interfaces, it has not been uncommon for drivers to break.
There are certainly plenty of PCMCIA problems, but they are mostly associated with resource allocation issues, PCI configuration issues, inadequate vendor documentation, etc.
> Indeed. I would wish to have at least cardbus support in the default > kernel, and eventually it will have to be written - the external pcmcia > support indeed relegates it to second-class citizen support. And > cardbus is much better done and defined than the original pcmcia anyway, > and is what all modern laptops use. > > However, I'm not going to just use the pcmcia code as-is, as David Hinds > has never been very excited about putting the support in the kernel. > And I do believe that for the old-style pcmcia stuff the current > approach is the right one anyway due to the ugly details. But if > somebody were to start up a cardbus driver system, I wouldn't be unhappy...
I think this is the first time I've ever heard you express interest in kernel support for dynamically configured devices. I'm somewhat unhappy that it sounds like you're encouraging someone else to do it differently.
"never been very excited" is a pretty accurate description of my feelings about putting the PCMCIA package in the kernel. I think some of the arguments for it have been weak. Having it out of the kernel makes my life easier in some ways, and that's a non-trivial consideration for me. I'm not dead-set against putting PCMCIA in the kernel, and anyone who felt strongly enough about it is free to just do it, though I'd prefer them to do it in a way that would make it easy to propagate updates from my tree to the kernel tree.
In some sense, PCMCIA and CardBus are second-class citizens because the Linux kernel is missing some key components that would make dynamic device management convenient and reliable. One of those is kernel support for Plug&Play BIOS calls, without which, resource allocation for hot-plug devices will always be a shot in the dark. ACPI will supercede this at some point, but my impression is that Linux ACPI support is still a long way from being comprehensive enough to handle this.
There are certainly things that would make CardBus support easier that would be very nice to have in the kernel: for instance, the current CardBus code has its own PCI device configurator because the kernel doesn't provide this functionality. Hot swap PCI will need to do the same stuff, so it should really be in the PCI subsystem. All the current CardBus drivers are just regular kernel PCI drivers, so CardBus is mostly already "in" the kernel source tree, in that sense.
-- Dave Hinds
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