Re: [Linaro-mm-sig] [RFC][PATCH 0/6] ion: improved ABI

[Laura Abbott]

On 06/06/2016 11:59 PM, Chen Feng wrote:
> The idea is good, define the heap ids in header file is inconvenient.
>
> But if we query the heaps information from user-space.
>
> It need to maintain this ids and name userspace one by one. The code may
> be complicated in different module user-space.
>
> In android, the gralloc and other lib will all use ion to alloc memory.
>
> This will make it more difficult to maintain user-space code.

This was a concern I had had as well. Anything that involves dynamic
probing is going to involve more tracking. Do you think some library
code in libion would help?

Thanks,
Laura

> But beyond this, The new alloc2 with not-handle flag is good.
> And the pull out of ioctl interface is also a good cleanup.
>
> On 2016/6/7 2:23, Laura Abbott wrote:
> > The ABI for Ion's ioctl interface are a pain to work with. The heap IDs
> > are a 32-bit non-discoverable namespace that form part of the ABI. There's
> > no way to determine what ABI version is in use which leads to problems
> > if the ABI changes or needs to be updated.
> >
> > This series is a first approach to give a better ABI for Ion. This includes:
> >
> > - Following the advice in botching-up-ioctls.txt
> > - Ioctl for ABI version
> > - Dynamic assignment of heap ids
> > - queryable heap ids
> > - Runtime mapping of heap ids, including fallbacks. This avoids the need to
> >   encode the fallbacks as an ABI.
> >
> > I'm most interested in feedback if this ABI is actually an improvement and
> > usable. The heap id map/query interface seems error prone but I didn't have
> > a cleaner solution. There aren't any kernel APIs for the new features as the
> > focus was on a userspace API but I anticipate that following easily once
> > the userspace API is established.
> >
> >
> > Thanks,
> > Laura
> >
> > P.S. Not to turn this into a bike shedding session but if you have suggestions
> > for a name for this framework other than Ion I would be interested to hear
> > them. Too many other things are already named Ion.
> >
> > Laura Abbott (6):
> >   staging: android: ion: return error value for ion_device_add_heap
> >   staging: android: ion: Switch to using an idr to manage heaps
> >   staging: android: ion: Drop heap type masks
> >   staging: android: ion: Pull out ion ioctls to a separate file
> >   staging: android: ion: Add an ioctl for ABI checking
> >   staging: android: ion: Introduce new ioctls for dynamic heaps
> >
> >  drivers/staging/android/ion/Makefile    |   3 +-
> >  drivers/staging/android/ion/ion-ioctl.c | 243 ++++++++++++++++++
> >  drivers/staging/android/ion/ion.c       | 438 ++++++++++++++++----------------
> >  drivers/staging/android/ion/ion_priv.h  | 109 +++++++-
> >  drivers/staging/android/uapi/ion.h      | 164 +++++++++++-
> >  5 files changed, 728 insertions(+), 229 deletions(-)
> >  create mode 100644 drivers/staging/android/ion/ion-ioctl.c