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    Subjectioctl arg passing
    Righto, first post to the list, here goes:

    I'm writing a char device driver for a dsp card that drives a motion
    platform. The basic flow is I basically have to reset the card and upload
    an executable file to it, and then poke the card to run it. Once this is
    done, I can issue instructions to the card/code to pass and return data
    from the card about the platform it's controlling.

    To pass the instructions I'm using a generic ioctl which passes the data
    between user & kernel-space using a struct which is basically like:

    struct instruction_t {
    __s16 code;
    __s16 rxlen;
    __s16 *rxbuf;
    __s16 txlen;
    __s16 *txbuf;

    (rx|tx)len is the length of the extra data that is provided/requested
    in/to be in (rx|tx)buf. Got me so far?

    Am I allowed to do this across the ioctl interface? In my ioctl
    "handler" I'm attempting to do:


    struct instruction_t local;
    __s16 *temp;

    copy_from_user( &local, ( struct instruction_t * ) arg, sizeof( struct instruction_t ) );
    temp = kmalloc( sizeof( __s16 ) * local.rxlen, GFP_KERNEL );
    copy_from_user( temp, arg, sizeof( __s16 ) * local.rxlen );
    local.rxbuf = temp;
    temp = kmalloc( sizeof( __s16 ) * local.txlen, GFP_KERNEL );


    Is this going to work as expected? Or am I gonna generate oops-a-plenty?



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