linux-kernel - Re: [RFC][PATCH 2/2] dma-buf: heaps: Allow system & cma heaps to be configured as a modules

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Date:   Mon, 4 Nov 2019 09:45:42 +0000
From:   Brian Starkey <Brian.Starkey@....com>
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>,
        "Andrew F . Davis" <afd@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "huyue2@...ong.com" <huyue2@...ong.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        nd <nd@....com>
Subject: Re: [RFC][PATCH 2/2] dma-buf: heaps: Allow system & cma heaps to be
 configured as a modules

Hi John,

On Fri, Oct 25, 2019 at 11:48:34PM +0000, John Stultz wrote:
> Allow loading system and cma heap as a module instead of just as
> a statically built in heap.
> 
> Since there isn't a good mechanism for dmabuf lifetime tracking
> it isn't safe to allow the heap drivers to be unloaded, so these
> drivers do not implement any module unloading functionality and
> will show up in lsmod as "[permanent]".

Cool, that alleviates my concerns :-)

> 
> This patch also exports key functions from dmabuf heaps core and
> the heap helper functions so they can be accessed by the module.
> 
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: Liam Mark <lmark@...eaurora.org>
> Cc: Pratik Patel <pratikp@...eaurora.org>
> Cc: Brian Starkey <Brian.Starkey@....com>
> Cc: Andrew F. Davis <afd@...com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Yue Hu <huyue2@...ong.com>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Chenbo Feng <fengc@...gle.com>
> Cc: Alistair Strachan <astrachan@...gle.com>
> Cc: Sandeep Patil <sspatil@...gle.com>
> Cc: Hridya Valsaraju <hridya@...gle.com>
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/dma-buf/dma-heap.c           | 2 ++
>  drivers/dma-buf/heaps/Kconfig        | 4 ++--
>  drivers/dma-buf/heaps/heap-helpers.c | 2 ++
>  3 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> index 9a41b73e54b4..2c4ac71a715b 100644
> --- a/drivers/dma-buf/dma-heap.c
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -161,6 +161,7 @@ void *dma_heap_get_drvdata(struct dma_heap *heap)
>  {
>  	return heap->priv;
>  }
> +EXPORT_SYMBOL_GPL(dma_heap_get_drvdata);
>  
>  struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  {
> @@ -243,6 +244,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  	kfree(heap);
>  	return err_ret;
>  }
> +EXPORT_SYMBOL_GPL(dma_heap_add);

Maybe overly picky - but adding the note about "no safe way to remove,
so there's no dma_heap_remove" to a comment on this function may be
easier to notice than in the git log alone.

Cheers,
-Brian

>  
>  static char *dma_heap_devnode(struct device *dev, umode_t *mode)
>  {
> diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
> index a5eef06c4226..e273fb18feca 100644
> --- a/drivers/dma-buf/heaps/Kconfig
> +++ b/drivers/dma-buf/heaps/Kconfig
> @@ -1,12 +1,12 @@
>  config DMABUF_HEAPS_SYSTEM
> -	bool "DMA-BUF System Heap"
> +	tristate "DMA-BUF System Heap"
>  	depends on DMABUF_HEAPS
>  	help
>  	  Choose this option to enable the system dmabuf heap. The system heap
>  	  is backed by pages from the buddy allocator. If in doubt, say Y.
>  
>  config DMABUF_HEAPS_CMA
> -	bool "DMA-BUF CMA Heap"
> +	tristate "DMA-BUF CMA Heap"
>  	depends on DMABUF_HEAPS && DMA_CMA
>  	help
>  	  Choose this option to enable dma-buf CMA heap. This heap is backed
> diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c
> index 750bef4e902d..fb9835126893 100644
> --- a/drivers/dma-buf/heaps/heap-helpers.c
> +++ b/drivers/dma-buf/heaps/heap-helpers.c
> @@ -24,6 +24,7 @@ void init_heap_helper_buffer(struct heap_helper_buffer *buffer,
>  	INIT_LIST_HEAD(&buffer->attachments);
>  	buffer->free = free;
>  }
> +EXPORT_SYMBOL_GPL(init_heap_helper_buffer);
>  
>  struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
>  					  int fd_flags)
> @@ -37,6 +38,7 @@ struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
>  
>  	return dma_buf_export(&exp_info);
>  }
> +EXPORT_SYMBOL_GPL(heap_helper_export_dmabuf);
>  
>  static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer)
>  {
> -- 
> 2.17.1
>