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SubjectRe: [RFC][PATCH 1/5 v2] dma-buf: Add dma-buf heaps framework
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On 3/6/19 1:03 PM, John Stultz wrote:
> On Wed, Mar 6, 2019 at 10:18 AM Andrew F. Davis <afd@ti.com> wrote:
>>
>> On 3/5/19 2:54 PM, John Stultz wrote:
>>> From: "Andrew F. Davis" <afd@ti.com>
>>>
>>> This framework allows a unified userspace interface for dma-buf
>>> exporters, allowing userland to allocate specific types of
>>> memory for use in dma-buf sharing.
>>>
>>> Each heap is given its own device node, which a user can
>>> allocate a dma-buf fd from using the DMA_HEAP_IOC_ALLOC.
>>>
>>> This code is an evoluiton of the Android ION implementation,
>>> and a big thanks is due to its authors/maintainers over time
>>> for their effort:
>>> Rebecca Schultz Zavin, Colin Cross, Benjamin Gaignard,
>>> Laura Abbott, and many other contributors!
>>>
>>> Cc: Laura Abbott <labbott@redhat.com>
>>> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>>> Cc: Greg KH <gregkh@linuxfoundation.org>
>>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
>>> Cc: Liam Mark <lmark@codeaurora.org>
>>> Cc: Brian Starkey <Brian.Starkey@arm.com>
>>> Cc: Andrew F. Davis <afd@ti.com>
>>> Cc: Chenbo Feng <fengc@google.com>
>>> Cc: Alistair Strachan <astrachan@google.com>
>>> Cc: dri-devel@lists.freedesktop.org
>>> Signed-off-by: Andrew F. Davis <afd@ti.com>
>>> [jstultz: reworded commit message, and lots of cleanups]
>>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>>> ---
>>> v2:
>>> * Folded down fixes I had previously shared in implementing
>>> heaps
>>> * Make flags a u64 (Suggested by Laura)
>>> * Add PAGE_ALIGN() fix to the core alloc funciton
>>> * IOCTL fixups suggested by Brian
>>> * Added fixes suggested by Benjamin
>>> * Removed core stats mgmt, as that should be implemented by
>>> per-heap code
>>> * Changed alloc to return a dma-buf fd, rather then a buffer
>>> (as it simplifies error handling)
>>> ---
>>> MAINTAINERS | 16 ++++
>>> drivers/dma-buf/Kconfig | 8 ++
>>> drivers/dma-buf/Makefile | 1 +
>>> drivers/dma-buf/dma-heap.c | 191 ++++++++++++++++++++++++++++++++++++++++++
>>> include/linux/dma-heap.h | 65 ++++++++++++++
>>> include/uapi/linux/dma-heap.h | 52 ++++++++++++
>>> 6 files changed, 333 insertions(+)
>>> create mode 100644 drivers/dma-buf/dma-heap.c
>>> create mode 100644 include/linux/dma-heap.h
>>> create mode 100644 include/uapi/linux/dma-heap.h
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index ac2e518..a661e19 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -4621,6 +4621,22 @@ F: include/linux/*fence.h
>>> F: Documentation/driver-api/dma-buf.rst
>>> T: git git://anongit.freedesktop.org/drm/drm-misc
>>>
>>> +DMA-BUF HEAPS FRAMEWORK
>>> +M: Laura Abbott <labbott@redhat.com>
>>> +R: Liam Mark <lmark@codeaurora.org>
>>> +R: Brian Starkey <Brian.Starkey@arm.com>
>>> +R: "Andrew F. Davis" <afd@ti.com>
>>
>> Quotes not needed in maintainers file.
>
> Whatever you say, "Andrew F. Davis", or whomever you really are! ;)
>

<_<
>_>
>
>>> +
>>> + if (heap_allocation.fd ||
>>> + heap_allocation.reserved0 ||
>>> + heap_allocation.reserved1 ||
>>> + heap_allocation.reserved2) {
>>
>> Seems too many reserved, I can understand one, but if we ever needed all
>> of these we would be better off just adding another alloc ioctl.
>
> Well, we have to have one u32 for padding. And I figured if we needed
> anything more then a u32, then we're in for 2 more.
>
> And I think the potential of the alignment and heap-private flags, I
> worry we might want to have something, but I guess we could just add
> a new ioctl and keep the support for the old one if folks prefer.
>
>>> +int dma_heap_add(struct dma_heap *heap)
>>> +{
>>> + struct device *dev_ret;
>>> + int ret;
>>> +
>>> + if (!heap->name || !strcmp(heap->name, "")) {
>>> + pr_err("dma_heap: Cannot add heap without a name\n");
>>
>> As these names end up as the dev name in the file system we may want to
>> check for invalid names, there is probably a helper for that somewhere.
>
> Hrm. I'll have to look.
>
>>> +struct dma_heap {
>>> + const char *name;
>>> + struct dma_heap_ops *ops;
>>> + unsigned int minor;
>>> + dev_t heap_devt;
>>> + struct cdev heap_cdev;
>>> +};
>>
>> Still not sure about this, all of the members in this struct are
>> strictly internally used by the framework. The users of this framework
>> should not have access to them and only need to deal with an opaque
>> pointer for tracking themselves (can store it in a private struct of
>> their own then container_of to get back out their struct).
>>
>> Anyway, not a big deal, and if it really bugs me enough I can always go
>> fix it later, it's all kernel internal so not a blocker here. :)
>
> I guess I'd just move the include/linux/dma-heap.h to
> drivers/dma-buf/heaps/ and keep it localized there.
> But whichever. Feel free to also send a patch and I can fold it down.
>

The dma-heap.h needs to stay where it is, I was thinking just move
struct dma_heap to inside drivers/dma-buf/dma-heap.c. I wouldn't worry
about changing anything right now though, I'll post a patch you can
squash in later one we confirm this whole dma-heap thing will get deemed
acceptable in the first place.

Thanks,
Andrew

> thanks
> -john
>

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