linux-kernel - Re: [PATCH v7 3/5] dma-buf: heaps: Add system heap to dmabuf heaps

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Date:   Thu, 25 Jul 2019 06:02:04 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Sudipto Paul <Sudipto.Paul@....com>,
        "Andrew F . Davis" <afd@...com>,
        Christoph Hellwig <hch@...radead.org>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v7 3/5] dma-buf: heaps: Add system heap to dmabuf heaps

> +struct system_heap {
> +	struct dma_heap *heap;
> +} sys_heap;

It seems like this structure could be removed and if would improve
the code flow.

> +static struct dma_heap_ops system_heap_ops = {
> +	.allocate = system_heap_allocate,
> +};
> +
> +static int system_heap_create(void)
> +{
> +	struct dma_heap_export_info exp_info;
> +	int ret = 0;
> +
> +	exp_info.name = "system_heap";
> +	exp_info.ops = &system_heap_ops;
> +	exp_info.priv = &sys_heap;
> +
> +	sys_heap.heap = dma_heap_add(&exp_info);
> +	if (IS_ERR(sys_heap.heap))
> +		ret = PTR_ERR(sys_heap.heap);
> +
> +	return ret;

The data structures here seem a little odd.  I think you want to:

 - mark all dma_heap_ops instanes consts, as we generally do that for
   all structures containing function pointers
 - move the name into dma_heap_ops.
 - remove the dma_heap_export_info structure, which is a bit pointless
 - don't bother setting a private data, as you don't need it.
   If other heaps need private data I'd suggest to switch to embedding
   the dma_heap structure into containing structure insted so that you
   can use container_of to get at it.
 - also why is the free callback passed as a callback rather than
   kept in dma_heap_ops, next to the paired alloc one?