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Sun, 11 Jan 2026 21:55:08 -0500 (EST) Date: Mon, 12 Jan 2026 11:55:06 +0900 From: Takashi Sakamoto To: linux1394-devel@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org, jgg@nvidia.com Subject: Re: [PATCH 0/8] firewire: core/ohci: code refactoring for pages dedicated to DMA Message-ID: <20260112025506.GA245601@workstation.local> Mail-Followup-To: linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, jgg@nvidia.com References: <20260110013911.19160-1-o-takashi@sakamocchi.jp> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260110013911.19160-1-o-takashi@sakamocchi.jp> 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