From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v7 3/5] dma-buf: heaps: Add system heap to dmabuf heaps
Date: Thu, 25 Jul 2019 06:02:04 -0700
Message-ID: <20190725130204.GG20286@infradead.org>
References: <20190724003656.59780-1-john.stultz@linaro.org>
 <20190724003656.59780-4-john.stultz@linaro.org>
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> +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?