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

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Date:	Tue, 7 Jun 2016 14:59:11 +0800
From:	Chen Feng <puck.chen@...ilicon.com>
To:	Laura Abbott <labbott@...hat.com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	John Stultz <john.stultz@...aro.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Riley Andrews <riandrews@...roid.com>
CC:	<devel@...verdev.osuosl.org>, Jon Medhurst <tixy@...aro.org>,
	"Android Kernel Team" <kernel-team@...roid.com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	<linux-kernel@...r.kernel.org>, <linaro-mm-sig@...ts.linaro.org>,
	"Jeremy Gebben" <jgebben@...eaurora.org>,
	Eun Taik Lee <eun.taik.lee@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [Linaro-mm-sig] [RFC][PATCH 0/6] ion: improved ABI

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.


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
>