[PATCH 6/9] Add a general, global device notification watch list [ver #5]

[Greg Kroah-Hartman]

On Fri, Jun 28, 2019 at 04:49:30PM +0100, David Howells wrote:
> Create a general, global watch list that can be used for the posting of
> device notification events, for such things as device attachment,
> detachment and errors on sources such as block devices and USB devices.
> This can be enabled with:
> 
> 	CONFIG_DEVICE_NOTIFICATIONS
> 
> To add a watch on this list, an event queue must be created and configured:
> 
>         fd = open("/dev/event_queue", O_RDWR);
>         ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, page_size << n);
> 
> and then a watch can be placed upon it using a system call:
> 
>         watch_devices(fd, 12, 0);
> 
> Unless the application wants to receive all events, it should employ
> appropriate filters.

What "filter"?  Who is going to use this and why a new system call for
this?  You can do this today with udev/netlink/hotplug/whatever so why
create yet-another-way?

I don't think this is a good idea unless we really nail down the api and
who is going to be using it.

thanks,

greg k-h