On Fri, 11 May 2018, Michael Schmitz wrote:
Perhaps you can add a new helper
(platform_device_register_simple_dma()?) that takes the DMA mask,
too?
...
So far, it looks like macmace and macsonic would be the only callers
of this new API call.
What's worse, if you do pass a dma_mask in struct
platform_device_info, you end up with this problem in
platform_device_register_full():
if (pdevinfo->dma_mask) {
/*
* This memory isn't freed when the device is put,
* I don't have a nice idea for that though. Conceptually
* dma_mask in struct device should not be a pointer.
* See http://thread.gmane.org/gmane.linux.kernel.pci/9081
*/
pdev->dev.dma_mask =
kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
Maybe platform_device_register_full() should rather check whether
dev.coherent_dma_mask is set, and make dev.dma_mask point to that? This
is how we solved the warning issue for the Zorro bus devices...
(8614f1b58bd0e920a5859464a500b93152c5f8b1)
The claim in the comment above that a pointer is the wrong solution
suggests that your proposal won't get far. Also, your proposal doesn't
address the other issues I raised: a new
platform_device_register_simple_dma() API would only have two callers, and
the dma mask setup for device-tree probed platform devices is apparently a
work-in-progress (which I don't want to churn up).
With people setting the mask to kill the WARNING splat, this may
become more common.
Since the commit which introduced the WARNING, only commits f61e64310b75
("m68k: set dma and coherent masks for platform FEC ethernets") and
7bcfab202ca7 ("powerpc/macio: set a proper dma_coherent_mask") seem to be
aimed at squelching that WARNING.
(Am I missing any others?)
Zorro devices :-)
Right, I should add commit 55496d3fe2ac ("zorro: Set up z->dev.dma_mask
for the DMA API") to that list.
Which begs the question: why can' you set up all Nubus bus devices' DMA
masks in nubus_device_register(), or nubus_add_board()?
I am expecting to see the same WARNING from the nubus sonic driver but it
hasn't happened yet, so I don't have a patch for it yet. In anycase, the
nubus fix would be a lot like the zorro bus fix, so I don't see a problem.
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