Re: DIOCGDISKINFO support for vnd

[Alan Barrett <apb%cequrux.com@localhost>]

On Tue, 11 Mar 2014, Patrick Welche wrote:
> The attached trivial patch allows vnd(4) to support generic disk ioctls.
> The only one in kern/subr_disk.c at the moment is DIOCGDISKINFO.
>
> Before:
> $ ./vndtest /dev/vnd0a 
> vndtest: DIOCGDISKINFO: Inappropriate ioctl for device
>
> After:
> $ ./vndtest /dev/vnd0a
> size of /dev/vnd0a: 524288 bytes

That's good, but ...

>         default:
> -               return ENOTTY;
> +               error = disk_ioctl(&vnd->sc_dkdev, cmd, data, flag, l);
> +               if (error == EPASSTHROUGH)
> +                       return ENOTTY;
> +               else
> +                       return error;

I think there's no need to translate EPASSTHROUGH to ENOTTY here; 
that translation will be done by sys_ioctl() before returning 
to userland.  Also, several other disk drivers have their ioctl 
handlers call disk_ioctl early (see fdioctl, wdioctl, sdioctl, 
dkioctl, raidioctl, among others), and it's not clear why vndioctl 
doesn't do that.

--apb (Alan Barrett)