Messages in this thread | | | Date | Mon, 5 Sep 2016 12:20:27 +0100 | From | Brian Starkey <> | Subject | Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks |
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Hi,
On Fri, Sep 02, 2016 at 12:36:25PM -0700, Laura Abbott wrote: >On 09/02/2016 06:41 AM, Brian Starkey wrote: >>Hi Laura, >> >>On Thu, Sep 01, 2016 at 03:40:41PM -0700, Laura Abbott wrote: >>> >>>There is no advantage to having heap types be a mask. The ion client has >>>long since dropped the mask. Drop the notion of heap type masks as well. >>> >> >>I know this is the same patch you sent last time, so sorry for not >>picking this up then - but I'm curious what "The" ion client is here? >> > >ion_client_create used to take a mask to indicate what heap types it >could allocate from. This hasn't been the case since 2bb9f5034ec7 >("gpu: ion: Remove heapmask from client"). "The ion client" probably >should have been "struct ion_client"
Ah I see, the in-kernel ion_client. Sorry, I completely forgot that even existed (because it's totally useless - how is a driver meant to find the global ion_device?)
> >>Our ion client(s) certainly still use these masks, and it's still >>used as a mask within ion itself - even if the relationship between a >>mask and a heap type has been somewhat lost. > >Where is it used in Ion? I don't see it in tree unless I missed something >and I'm not eager to keep this around for out of tree code. What's the >actual use for this?
You're certainly right that these heap-ID-to-allocation-mask macros are unused in the kernel, but I don't really see the reason for removing them - they are convenient (for now).
Example: I'm using the dummy ion driver, and I want to allocate from the SYSTEM_CONTIG heap - the ION_HEAP_SYSTEM_CONTIG_MASK gives me the exact mask I need for that.
It seems your opinion is that heap-IDs are already, and should be, completely decoupled from their type. That sounds like a good idea to me, but it's not true (yet) - again check out the dummy driver.
At the moment, heap-IDs are assigned by ion drivers in any way they see fit. For as long as that stays the case there's always going to be heap-masks hard-coded in UAPI kernel headers (in-tree or not), so removing these particular masks seems a bit fruitless.
I'd rather see driver-assigned heap-IDs disappear completely, and have them assigned by ion core from an idr or something. At that point these macros really *are* meaningless, and I'd be totally fine with removing them (and userspace won't be able to depend on hard-coded allocation masks any more - it will have to use the query ioctl, which I assume is the whole point?).
IMO it's not the right time to remove these macros, because they still have meaning and usefulness.
Cheers, Brian
> >> >>Thanks, >>Brian >> >>>Signed-off-by: Laura Abbott <labbott@redhat.com> >>>--- >>>drivers/staging/android/uapi/ion.h | 6 ------ >>>1 file changed, 6 deletions(-) >>> >>>diff --git a/drivers/staging/android/uapi/ion.h b/drivers/staging/android/uapi/ion.h >>>index 0a8e40f..a9c4e8b 100644 >>>--- a/drivers/staging/android/uapi/ion.h >>>+++ b/drivers/staging/android/uapi/ion.h >>>@@ -44,14 +44,8 @@ enum ion_heap_type { >>> * must be last so device specific heaps always >>> * are at the end of this enum >>> */ >>>- ION_NUM_HEAPS = 16, >>>}; >>> >>>-#define ION_HEAP_SYSTEM_MASK (1 << ION_HEAP_TYPE_SYSTEM) >>>-#define ION_HEAP_SYSTEM_CONTIG_MASK (1 << ION_HEAP_TYPE_SYSTEM_CONTIG) >>>-#define ION_HEAP_CARVEOUT_MASK (1 << ION_HEAP_TYPE_CARVEOUT) >>>-#define ION_HEAP_TYPE_DMA_MASK (1 << ION_HEAP_TYPE_DMA) >>>- >>>#define ION_NUM_HEAP_IDS (sizeof(unsigned int) * 8) >>> >>>/** >>>-- >>>2.7.4 >>> >
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