linux-kernel - Re: [RFC PATCH 06/12] staging: android: ion: Remove crufty cache support

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Date:   Fri, 3 Mar 2017 10:46:03 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Daniel Vetter <daniel@...ll.ch>, devel@...verdev.osuosl.org,
        romlem@...gle.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        arve@...roid.com, linux-kernel@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
        Riley Andrews <riandrews@...roid.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [RFC PATCH 06/12] staging: android: ion: Remove crufty cache
 support

On 03/03/2017 08:39 AM, Laurent Pinchart wrote:
> Hi Daniel,
> 
> On Friday 03 Mar 2017 10:56:54 Daniel Vetter wrote:
>> On Thu, Mar 02, 2017 at 01:44:38PM -0800, Laura Abbott wrote:
>>> Now that we call dma_map in the dma_buf API callbacks there is no need
>>> to use the existing cache APIs. Remove the sync ioctl and the existing
>>> bad dma_sync calls. Explicit caching can be handled with the dma_buf
>>> sync API.
>>>
>>> Signed-off-by: Laura Abbott <labbott@...hat.com>
>>> ---
>>>
>>>  drivers/staging/android/ion/ion-ioctl.c         |  5 ----
>>>  drivers/staging/android/ion/ion.c               | 40 --------------------
>>>  drivers/staging/android/ion/ion_carveout_heap.c |  6 ----
>>>  drivers/staging/android/ion/ion_chunk_heap.c    |  6 ----
>>>  drivers/staging/android/ion/ion_page_pool.c     |  3 --
>>>  drivers/staging/android/ion/ion_system_heap.c   |  5 ----
>>>  6 files changed, 65 deletions(-)
>>>
>>> diff --git a/drivers/staging/android/ion/ion-ioctl.c
>>> b/drivers/staging/android/ion/ion-ioctl.c index 5b2e93f..f820d77 100644
>>> --- a/drivers/staging/android/ion/ion-ioctl.c
>>> +++ b/drivers/staging/android/ion/ion-ioctl.c
>>> @@ -146,11 +146,6 @@ long ion_ioctl(struct file *filp, unsigned int cmd,
>>> unsigned long arg)> 
>>>  			data.handle.handle = handle->id;
>>>  		
>>>  		break;
>>>  	
>>>  	}
>>>
>>> -	case ION_IOC_SYNC:
>>> -	{
>>> -		ret = ion_sync_for_device(client, data.fd.fd);
>>> -		break;
>>> -	}
>>
>> You missed the case ION_IOC_SYNC: in compat_ion.c.
>>
>> While at it: Should we also remove the entire custom_ioctl infrastructure?
>> It's entirely unused afaict, and for a pure buffer allocator I don't see
>> any need to have custom ioctl.
> 
> I second that, if you want to make ion a standard API, then we certainly don't 
> want any custom ioctl.
> 
>> More code to remove potentially:
>> - The entire compat ioctl stuff - would be an abi break, but I guess if we
>>   pick the 32bit abi and clean up the uapi headers we'll be mostly fine.
>>   would allow us to remove compat_ion.c entirely.
>>
>> - ION_IOC_IMPORT: With this ion is purely an allocator, so not sure we
>>   still need to be able to import anything. All the cache flushing/mapping
>>   is done through dma-buf ops/ioctls.
>>
>>

Good point to all of the above. I was considering keeping the import around
for backwards compatibility reasons but given how much other stuff is being
potentially broken, everything should just get ripped out.

Thanks,
Laura