From owner-freebsd-scsi  Sat Mar  4  3: 7:18 2000
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Date: Sat, 04 Mar 2000 15:02:45 +0530
From: Nanda Kumar <nanda@procsys.com>
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To: Mike Smith <msmith@freebsd.org>
Cc: freebsd-scsi@FreeBSD.ORG
Subject: Re: IOCTL support in SCSI block driver
References: <200003032231.OAA01856@mass.cdrom.com>
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Hi,

I didn't find the make_dev() function in FreeBSD 3.4 version. Is there
any equivalent function to mak_edev ()
in 3.4 ? Does the make_dev () creates an inode also for the device ?

Regards,
Nandan

>Mike Smith wrote:
> 
> > I am just resending the mail. After going through the code i am almost
> > lost.
> >
> >  I went through the mylex code to find how they implement the control
> >  interface. But i have some doubts regarding this. Mainly these doubts
> >  come since i am still quiete new to the FreeBSD world and don't have
> >  good text books regarding how to write device drivers etc.
> >
> >  1). In the user space how do i specify a controller to communicate with
> >  that ? For eg. if i want to open the device and a send an IOCTL how do
> > i specify that ? In our case actual disks will be seen as part of target
> >  discovery done through the CAM SCSI interface.
> 
> The controller code instantiates a device for each controller.  The Mylex
> driver is still doing this the "old" way:
> 
>     /*
>      * Register the control device on first attach.
>      */
>     if (cdev_registered++ == 0)
>         cdevsw_add(&mlx_cdevsw);
> 
> It would be more correct for it to use:
> 
>     sc->mlx_dev_t = make_dev(&mlx_cdevsw, device_get_unit(sc->mlx_dev),
>                              0, 0, S_IRUSR|S_IRUSRW,
>                              "mlx%d", device_get_unit(sc->mlx_dev));
> 
> and then use
> 
>     destroy_dev(sc->mlx_dev_t);
> 
> in the corresponding detach method.
> 
> (makes note to self to fix Mylex driver thusly).
> 
> >  2). I found that the while registering the character device the "softc"
> >  structure does not come to picture at all. But later while opening the
> >  device the "softc" structure is obtained using "devclass_get_softc".
> > How is it obtained ? If there are some documents regarding these you can
> >  tell me and i will go through it.
> 
> The bus code is responsible for tracking the softc structure; the minor
> number for the device maps directly to the controller instance number, so
> /dev/mlx0 has minor number 0, and thus you ask for the softc pointer for
> instance 0 of mlx_devclass.
> 
> --
> \\ Give a man a fish, and you feed him for a day. \\  Mike Smith
> \\ Tell him he should learn how to fish himself,  \\  msmith@freebsd.org
> \\ and he'll hate you for a lifetime.             \\  msmith@cdrom.com


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