Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of staging

[Laurent Pinchart]

Hi Laura,

Thank you for the patches.

On Thursday 02 Mar 2017 13:44:32 Laura Abbott wrote:
> Hi,
> 
> There's been some recent discussions[1] about Ion-like frameworks. There's
> apparently interest in just keeping Ion since it works reasonablly well.
> This series does what should be the final clean ups for it to possibly be
> moved out of staging.
> 
> This includes the following:
> - Some general clean up and removal of features that never got a lot of use
>   as far as I can tell.
> - Fixing up the caching. This is the series I proposed back in December[2]
>   but never heard any feedback on. It will certainly break existing
>   applications that rely on the implicit caching. I'd rather make an effort
>   to move to a model that isn't going directly against the establishement
>   though.
> - Fixing up the platform support. The devicetree approach was never well
>   recieved by DT maintainers. The proposal here is to think of Ion less as
>   specifying requirements and more of a framework for exposing memory to
>   userspace.

That's where most of my concerns with ion are. I still strongly believe that 
the heap-based approach is inherently flawed, as it would need to be 
configured for each device according to product-specific use cases. That's not 
something that could be easily shipped with a generic distribution. We should 
replace that with a constraint-based system.

> - CMA allocations now happen without the need of a dummy device structure.
>   This fixes a bunch of the reasons why I attempted to add devicetree
>   support before.
> 
> I've had problems getting feedback in the past so if I don't hear any major
> objections I'm going to send out with the RFC dropped to be picked up.
> The only reason there isn't a patch to come out of staging is to discuss any
> other changes to the ABI people might want. Once this comes out of staging,
> I really don't want to mess with the ABI.
> 
> Feedback appreciated.
> 
> Thanks,
> Laura
> 
> [1] https://marc.info/?l=linux-kernel&m=148699712602105&w=2
> [2] https://marc.info/?l=linaro-mm-sig&m=148176050802908&w=2
> 
> Laura Abbott (12):
>   staging: android: ion: Remove dmap_cnt
>   staging: android: ion: Remove alignment from allocation field
>   staging: android: ion: Duplicate sg_table
>   staging: android: ion: Call dma_map_sg for syncing and mapping
>   staging: android: ion: Remove page faulting support
>   staging: android: ion: Remove crufty cache support
>   staging: android: ion: Remove old platform support
>   cma: Store a name in the cma structure
>   cma: Introduce cma_for_each_area
>   staging: android: ion: Use CMA APIs directly
>   staging: android: ion: Make Ion heaps selectable
>   staging; android: ion: Enumerate all available heaps
> 
>  drivers/base/dma-contiguous.c                      |   5 +-
>  drivers/staging/android/ion/Kconfig                |  51 ++--
>  drivers/staging/android/ion/Makefile               |  14 +-
>  drivers/staging/android/ion/hisilicon/Kconfig      |   5 -
>  drivers/staging/android/ion/hisilicon/Makefile     |   1 -
>  drivers/staging/android/ion/hisilicon/hi6220_ion.c | 113 ---------
>  drivers/staging/android/ion/ion-ioctl.c            |   6 -
>  drivers/staging/android/ion/ion.c                  | 282 +++++-------------
>  drivers/staging/android/ion/ion.h                  |   5 +-
>  drivers/staging/android/ion/ion_carveout_heap.c    |  16 +-
>  drivers/staging/android/ion/ion_chunk_heap.c       |  15 +-
>  drivers/staging/android/ion/ion_cma_heap.c         | 102 ++------
>  drivers/staging/android/ion/ion_dummy_driver.c     | 156 ------------
>  drivers/staging/android/ion/ion_enumerate.c        |  89 +++++++
>  drivers/staging/android/ion/ion_of.c               | 184 --------------
>  drivers/staging/android/ion/ion_of.h               |  37 ---
>  drivers/staging/android/ion/ion_page_pool.c        |   3 -
>  drivers/staging/android/ion/ion_priv.h             |  57 ++++-
>  drivers/staging/android/ion/ion_system_heap.c      |  14 +-
>  drivers/staging/android/ion/tegra/Makefile         |   1 -
>  drivers/staging/android/ion/tegra/tegra_ion.c      |  80 ------
>  include/linux/cma.h                                |   6 +-
>  mm/cma.c                                           |  25 +-
>  mm/cma.h                                           |   1 +
>  mm/cma_debug.c                                     |   2 +-
>  25 files changed, 312 insertions(+), 958 deletions(-)
>  delete mode 100644 drivers/staging/android/ion/hisilicon/Kconfig
>  delete mode 100644 drivers/staging/android/ion/hisilicon/Makefile
>  delete mode 100644 drivers/staging/android/ion/hisilicon/hi6220_ion.c
>  delete mode 100644 drivers/staging/android/ion/ion_dummy_driver.c
>  create mode 100644 drivers/staging/android/ion/ion_enumerate.c
>  delete mode 100644 drivers/staging/android/ion/ion_of.c
>  delete mode 100644 drivers/staging/android/ion/ion_of.h
>  delete mode 100644 drivers/staging/android/ion/tegra/Makefile
>  delete mode 100644 drivers/staging/android/ion/tegra/tegra_ion.c

-- 
Regards,

Laurent Pinchart