staging: android: ion: aligned allocation support

Alexey Skidanov alexey.skidanov at intel.com
Wed Oct 3 20:03:25 UTC 2018



On 10/03/2018 09:07 PM, Laura Abbott wrote:
> On 10/02/2018 07:27 AM, Alexey Skidanov wrote:
>> Hi,
>>
>> Sometimes HW requires memory buffer to be aligned in order to be used
>> properly.  Of course, we may overcome the lack of aligned allocation
>> support, but we may easily add it because CMA and gen_pool (used by
>> several heaps) already support it.
>>
>> Does someone have an objection to add it?
>>
>> Thanks,
>> Alexey
>>
> 
> The alignment option was removed from the allocation API before
> because the most common heap (system heap) didn't support it
> and it was causing more confusion. We've already mangled the
> ABI once so I really don't want to break it again. I'm not
> opposed to adding alignment support for the CMA via the allocation
> flags. 
Currently, the flags member is used to define the way the buffer will be
mapped - cached or uncached. So,if I understand you correct, we need to
add ION_FLAG_ALIGNED flag and to share 32 bit field between flags and
flags specific data (alignment value) ?

I'm probably going to remove the carveout and chunk heap because
> nobody has stepped up to figure out how to tie allocation of those
> to device tree or another method.
> 
> Thanks,
> Laura

Thanks,
Alexey


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