[PATCH v3 2/2] staging: ion: create one device entry per heap

[Laura Abbott]

On 09/20/2017 01:45 AM, Benjamin Gaignard wrote:
> Instead a getting one common device "/dev/ion" for
> all the heaps this patch allow to create one device
> entry ("/dev/ionX") per heap.
> Getting an entry per heap could allow to set security rules
> per heap and global ones for all heaps.
> 
> Allocation requests will be only allowed if the mask_id
> match with device minor.
> Query request could be done on any of the devices.
> Deivce node major will also change and that may impact init scripts.
> 

We should start Cc linux-api for future changes since we're going
to have more than just /dev/ion.

Thinking about this some more, I think we need to allow backwards
compatibility. It's just not feasible to keep throwing workarounds
into userspace if we can avoid it. I'd propose keeping the old /dev/ion
misc interface available under a Kconfig and then creating the new
split heaps in parallel.

On a somewhat related note, there was some interest in possibly
having a sysfs interface for Ion long term. I don't think this
needs to happen right now but I'd like whatever we do to not
make adding that harder.

Thanks,
Laura