On Sat, Jan 10, 2026 at 10:39:03AM +0900, Takashi Sakamoto wrote:
> Hi,
>
> This patchset is to refactor current codes handling pages dedicated to
> DMA.
>
> There are two cases to acquires pages dedicated to DMA; isochronous
> contexts and AR contexts. The reason of page acquisition is the need to map
> them into VMA. In the former case, they are mapped into userspace VMA. In
> the latter case, they are mapped into kernel VMA with continuous address
> to access to packet content across the page boundaries, especially between
> the end and the beginning of pages. The allocated pages are
> discontiguous, and their cache coherency is managed by DMA streaming
> APIs.
>
> 1394 OHCI has no restriction about the size and alignment of memory
> registered for DMA, while the registered DMA address should be within
> 32 bit. The DMA mapped addresses can be discontiguous between descriptor,
> thus the above subsystem design is due to the convenience of system side.
>
> I think the recent convention of driver programming relies on DMA-coherent
> buffers, while this code refactoring keeps the uses of DMA streaming
> APIs as is. Also, the acquisition per page is kept as is, even if there
> are some ways to allocate memories wider than the page size. They would be
> future works since it requires to change how to handle the packet content
> across the pages.
>
>
> Takashi Sakamoto (8):
> firewire: core: move private function declaration from public header
> to internal header
> firewire: core: use mutex instead of spinlock for client isochronous
> context
> firewire: core: code refactoring with cleanup function for isoc pages
> firewire: core: use common kernel API to allocate and release a batch
> of pages
> firewire: core: stop using page private to store DMA mapping address
> firewire: ohci: use MAX macro to guarantee minimum count of pages for
> AR contexts
> firewire: ohci: split page allocation from dma mapping
> firewire: ohci: stop using page private to store DMA mapping address
>
> drivers/firewire/core-cdev.c | 41 ++++++------
> drivers/firewire/core-iso.c | 86 +++++++++++++-----------
> drivers/firewire/core.h | 1 +
> drivers/firewire/ohci.c | 124 ++++++++++++++++++++---------------
> include/linux/firewire.h | 3 +-
> 5 files changed, 141 insertions(+), 114 deletions(-)
Applied to for-next branch.
Regards
Takashi Sakamoto