Re: Dynamic modules

[Paul Goyette <paul%vps1.whooppee.com@localhost>]

On Mon, 4 May 2015, Kamil Rytarowski wrote:


> 3. Is it possible to automatically create a device file in /dev from a
>    module?

Not really, at least not from a loaded kernel module.

On the other hand, modules are also applicable to "rump" environments, 
and you _can_ dynamically create the /dev entry (in a rump'd file 
system, of course).  For an example, please have a look at

	src/sys/rump/dev/lib/libsysmon/sysmon_component.c

> 4. What is the best way to extract the major from devsw_attach call in
>    case we let it to automatically generate the major? For now I'm
>    using printf(9) and I'm checking dmesg(8). This gives me an output
>    for mknod(8) with an appropriate value.

You could always create a sysctl and make the return values from 
devsw_attach() available to user-land.

BTW, devsw_attach() doesn't "automatically generate the major".  It does 
a lookup in the majors table.  If there is no entry in the table, you 
get an error.

(At least, that's how I read that code.  If I've misinterpreted, I'd be 
happy to have someone explain how it really works!)


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