[RFC][PATCH 0/2] Allow DMA BUF heaps to be loaded as modules

[Daniel Vetter]

On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
> Now that the DMA BUF heaps core code has been queued, I wanted
> to send out some of the pending changes that I've been working
> on.
> 
> For use with Android and their GKI effort, it is desired that
> DMA BUF heaps are able to be loaded as modules. This is required
> for migrating vendors off of ION which was also recently changed
> to support modules.
> 
> So this patch series simply provides the necessary exported
> symbols and allows the system and CMA drivers to be built
> as modules.
> 
> Due to the fact that dmabuf's allocated from a heap may
> be in use for quite some time, there isn't a way to safely
> unload the driver once it has been loaded. Thus these
> drivers do no implement module_exit() functions and will
> show up in lsmod as "[permanent]"
> 
> Feedback and thoughts on this would be greatly appreciated!

Do we actually want this?

I figured if we just state that vendors should set up all the right
dma-buf heaps in dt, is that not enough?

Exporting symbols for no real in-tree users feels fishy.
-Daniel

> 
> thanks
> -john
> 
> Cc: Laura Abbott <labbott at redhat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: Liam Mark <lmark at codeaurora.org>
> Cc: Pratik Patel <pratikp at codeaurora.org>
> Cc: Brian Starkey <Brian.Starkey at arm.com>
> Cc: Andrew F. Davis <afd at ti.com>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Yue Hu <huyue2 at yulong.com>
> Cc: Mike Rapoport <rppt at linux.ibm.com>
> Cc: Chenbo Feng <fengc at google.com>
> Cc: Alistair Strachan <astrachan at google.com>
> Cc: Sandeep Patil <sspatil at google.com>
> Cc: Hridya Valsaraju <hridya at google.com>
> Cc: dri-devel at lists.freedesktop.org
> 
> John Stultz (1):
>   dma-buf: heaps: Allow system & cma heaps to be configured as a modules
> 
> Sandeep Patil (1):
>   mm: cma: Export cma symbols for cma heap as a module
> 
>  drivers/dma-buf/dma-heap.c           | 2 ++
>  drivers/dma-buf/heaps/Kconfig        | 4 ++--
>  drivers/dma-buf/heaps/heap-helpers.c | 2 ++
>  kernel/dma/contiguous.c              | 1 +
>  mm/cma.c                             | 5 +++++
>  5 files changed, 12 insertions(+), 2 deletions(-)
> 
> -- 
> 2.17.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch