Re: [RFC PATCH 2/9] ntsync: Reserve a minor device number and ioctl range.

Elizabeth Figura
2024-01-24T03:43:12Z

On Tuesday, 23 January 2024 18:54:02 CST Greg Kroah-Hartman wrote:
> On Tue, Jan 23, 2024 at 06:40:21PM -0600, Elizabeth Figura wrote:
> > Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
> > ---
>
> Note, we can't take patches without any changelog text, and you don't
> want us to :)
>
> > Documentation/admin-guide/devices.txt | 3 ++-
> > Documentation/userspace-api/ioctl/ioctl-number.rst | 2 ++
> > drivers/misc/ntsync.c | 3 ++-
> > include/linux/miscdevice.h | 1 +
> > 4 files changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/devices.txt
> > b/Documentation/admin-guide/devices.txt index 94c98be1329a..041404397ee5
> > 100644
> > --- a/Documentation/admin-guide/devices.txt
> > +++ b/Documentation/admin-guide/devices.txt
> > @@ -376,8 +376,9 @@
> >
> > 240 = /dev/userio Serio driver testing device
> > 241 = /dev/vhost-vsock Host kernel driver for virtio
vsock
> > 242 = /dev/rfkill Turning off radio transmissions
(rfkill)
> >
> > + 243 = /dev/ntsync NT synchronization primitive
device
> >
> > - 243-254 Reserved for local use
> > + 244-254 Reserved for local use
>
> Why do you need a fixed minor number? Can't your userspace handle
> dynamic numbers? What systems require a static value?

I believe I added this because it's necessary for MODULE_ALIAS (and, more
broadly, because I was following the example of vaguely comparable devices
like /dev/loop-control). I suppose I could instead just remove MODULE_ALIAS
(or even remove the ability to compile ntsync as a module entirely).

It's a bit difficult to figure out what's the preferred way to organize things
like this (there not being a lot of precedent for this kind of driver) so I'd
appreciate any direction.

--Zeb