On Sun, Sep 07, 2025 at 11:25:09PM +0900, Takashi Sakamoto wrote:

Hi,

I'm a present maintainer of Linux FireWire subsystem, and recent years
have been working to modernize the subsystem.

On Fri, Sep 05, 2025 at 14:43:24PM -0300, Jason Gunthorpe wrote:

quoted

There is only one user I found of alloc_pages:

drivers/firewire/ohci.c:                ctx->pages[i] = dma_alloc_pages(dev, PAGE_SIZE, &dma_addr,

And it deliberately uses page->private:

	set_page_private(ctx->pages[i], dma_addr);

So it is correct to use the struct page API.

I've already realized it, and it is in my TODO list to use modern
alternative APIs to replace it (but not yet). If you know some
candidates for this purpose, it is really helpful to accomplish it.

I think for now it is probably OKish, but in the medium/longer term
this probably wants to have its own memdesc like other cases.

Ie instead of using page->private you'd have a

struct ohci_desc {
	unsigned long __page_flags;
	dma_addr_t dma_addr;
[..]
};

And instead of using page->private you'd use ohci_desc::dma_addr.

This would require changing dma_alloc_pages() to be able to allocate
the frozen memdescs..

Which we are not quite there yet, but maybe come back to this in 2026?

Jason