Re: preferable way to control kernel module

From: Sergey Uvarov (uvarovsl_at_mail.pnpi.spb.ru)
Date: 08/10/05

  • Next message: alexander: "Re: Using sysarch specific syscalls in assembly?"
    Date: Thu, 11 Aug 2005 01:50:44 +0400
    To: John Baldwin <jhb@freebsd.org>
    
    

    >>>>I'm writing a kernel module for my own needs. AFAIK the following
    >>>>methods could be used:
    >>>>
    >>>>1) allocate not used system call with help of SYSCALL_MODULE macro
    >>>>
    >>>>2) allocate proprieatry oid via SYSCTL_OID(OID_AUTO) and write an
    >>>>appropriate sysctl handler(s)
    >>>>
    >>>>3) add a file in /dev and use ioctl(2) call
    >>>>
    >>>>What is a preferable way to control my module?
    >>>
    >>>It depends on what you want to do really. I've used sysctl's for simple
    >>>debug modules where I write to the sysctl to have it perform a desired
    >>>action.
    >>
    >>I need to pass some configuration parameters to my module and retrieve a
    >>status back. Interface is quite similar to ptrace(2) syscall. I don't
    >>need to pass large amount of data.
    >
    >
    > If it's a single integer or some such, I'd say use sysctl. If it's a
    > structure, I'd go the ioctl(2) route. Creating /dev entries isn't all that
    > hard. In your case you'd just need open/close/ioctl in a cdevsw, then use
    > make_dev() during MOD_LOAD and destroy_dev() during MOD_UNLOAD.
    >

    Thank you for advise. But I wonder: what is wrong with syscall approach
    (via SYSCALL_MODULE macro)?

    Thanks again,
            Sergey.
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