On 09/25/2017 11:56 PM, Greg KH wrote:
On Tue, Sep 26, 2017 at 07:09:14AM +0200, Daniel Vetter wrote:
On Mon, Sep 25, 2017 at 11:26:27AM -0700, Laura Abbott wrote:
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.
Not sure sysfs is a good idea for allocating buffers. The backlight
interface is in sysfs, which defacto makes it a root-only interface.
Distros really hate that, because it makes unpriviledged X/wayland really
hard to pull of. Passing a device file otoh from logind to the compositor
is dead simple (and how X et al get at e.g. the drm/input devices
already).
sysfs is not a good idea for allocating buffers. We already have some
out-of-tree drm drivers doing horrid things in sysfs in ways that
totally abuse that api, and vendors have to do crazy things with selinux
rules to try to lock it down because of that. A device node is fine, we
are used to that for graphics stuff :)
thanks,
greg k-h
I wasn't thinking of sysfs for allocation, this was for exposure of
other Ion information that might make more sense than debugfs. Like
I said, this was mostly forward thinking to make sure we aren't
stuck later.
Thanks,
Laura
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