Date: Fri, 03 Oct 1997 20:30:40 -0700 From: Julian Elischer <julian@whistle.com> To: mdean <mdean@best.com> Cc: freebsd-hackers@freebsd.org Subject: Re: lkms versus hard linked drivers Message-ID: <3435B860.19A13460@whistle.com> References: <Pine.SGI.3.95.971003185032.22045A-100000@shellx.best.com>
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mdean wrote: > > My question is very simple: What can't be a lkm? > For instance if I have some intel 8255As that I am going to use to produce > a 500hz pulse train for stepper motor control. These chips aren't stateless > and need to be intialized and mostly need to be kernel code to access > change of state interrupts and the high frequency clock (obviously). Can I > do all this from an lkm? yes sure. the only function that MUST be done at bootup is allocation of LARGE physically contiguous buffers of ram. because after running a few seconds ram get's fragmented.. large VIRTUALLY contiguous buffers are ok. I'm not sure about interrupts in the present code.. > > Will everything except the boot device driver and microkernel eventually be > an lkm? yes > Is it undesirable or something, because the only module that I am > using on my system is for the screensaver? no there are a few pieces of the puzzle still not quite ready. check the LKM examples in /usr/share/exaples/lkm as well. > > What about this: I am pretty sure I cannot do this inside the kernel. What > if I want my device driver for the stepper motor to socket(2) since it is > really not going to have any ioctls. This way controlling motor position > can be done from any machine on the network. of course it can be done.. but it may be better to have a daemon do that part.. > > Can I use any system call in a) device driver in the kernel tree b) lkm? no, and no.
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