linux-kernel - [PATCH 8/8] firewire: ohci: stop using page private to store DMA mapping address

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Message-ID: <20260110013911.19160-9-o-takashi@sakamocchi.jp>
Date: Sat, 10 Jan 2026 10:39:11 +0900
From: Takashi Sakamoto <o-takashi@...amocchi.jp>
To: linux1394-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org,
	jgg@...dia.com
Subject: [PATCH 8/8] firewire: ohci: stop using page private to store DMA mapping address

There is a long discussion about the use of private field in page
structure between Linux kernel developers.

This commit stop using page private to store DMA mapping address for
AR context, to prepare for mm future change.

Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
 drivers/firewire/ohci.c | 39 ++++++++++++++++-----------------------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index e34965acb925..a43fe680d508 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -96,6 +96,7 @@ struct ar_context {
 	struct fw_ohci *ohci;
 	struct page *pages[AR_BUFFERS];
 	void *buffer;
+	dma_addr_t dma_addrs[AR_BUFFERS];
 	struct descriptor *descriptors;
 	dma_addr_t descriptors_bus;
 	void *pointer;
@@ -513,11 +514,6 @@ static int ohci_update_phy_reg(struct fw_card *card, int addr,
 	return update_phy_reg(ohci, addr, clear_bits, set_bits);
 }
 
-static inline dma_addr_t ar_buffer_bus(struct ar_context *ctx, unsigned int i)
-{
-	return page_private(ctx->pages[i]);
-}
-
 static void ar_context_link_page(struct ar_context *ctx, unsigned int index)
 {
 	struct descriptor *d;
@@ -544,11 +540,11 @@ static void ar_context_release(struct ar_context *ctx)
 		return;
 
 	for (int i = 0; i < AR_BUFFERS; ++i) {
-		dma_addr_t dma_addr = page_private(ctx->pages[i]);
-
-		dma_unmap_page(dev, dma_addr, PAGE_SIZE, DMA_FROM_DEVICE);
-		set_page_private(ctx->pages[i], 0);
+		dma_addr_t dma_addr = ctx->dma_addrs[i];
+		if (dma_addr)
+			dma_unmap_page(dev, dma_addr, PAGE_SIZE, DMA_FROM_DEVICE);
 	}
+	memset(ctx->dma_addrs, 0, sizeof(ctx->dma_addrs));
 
 	vunmap(ctx->buffer);
 	ctx->buffer = NULL;
@@ -647,14 +643,12 @@ static void ar_sync_buffers_for_cpu(struct ar_context *ctx,
 
 	i = ar_first_buffer_index(ctx);
 	while (i != end_buffer_index) {
-		dma_sync_single_for_cpu(ctx->ohci->card.device,
-					ar_buffer_bus(ctx, i),
-					PAGE_SIZE, DMA_FROM_DEVICE);
+		dma_sync_single_for_cpu(ctx->ohci->card.device, ctx->dma_addrs[i], PAGE_SIZE,
+					DMA_FROM_DEVICE);
 		i = ar_next_buffer_index(i);
 	}
 	if (end_buffer_offset > 0)
-		dma_sync_single_for_cpu(ctx->ohci->card.device,
-					ar_buffer_bus(ctx, i),
+		dma_sync_single_for_cpu(ctx->ohci->card.device, ctx->dma_addrs[i],
 					end_buffer_offset, DMA_FROM_DEVICE);
 }
 
@@ -795,9 +789,8 @@ static void ar_recycle_buffers(struct ar_context *ctx, unsigned int end_buffer)
 
 	i = ar_first_buffer_index(ctx);
 	while (i != end_buffer) {
-		dma_sync_single_for_device(ctx->ohci->card.device,
-					   ar_buffer_bus(ctx, i),
-					   PAGE_SIZE, DMA_FROM_DEVICE);
+		dma_sync_single_for_device(ctx->ohci->card.device, ctx->dma_addrs[i], PAGE_SIZE,
+					   DMA_FROM_DEVICE);
 		ar_context_link_page(ctx, i);
 		i = ar_next_buffer_index(i);
 	}
@@ -850,6 +843,7 @@ static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
 	struct device *dev = ohci->card.device;
 	unsigned int i;
 	struct page *pages[AR_BUFFERS + AR_WRAPAROUND_PAGES];
+	dma_addr_t dma_addrs[AR_BUFFERS];
 	void *vaddr;
 	struct descriptor *d;
 
@@ -885,19 +879,18 @@ static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
 		dma_addr_t dma_addr = dma_map_page(dev, pages[i], 0, PAGE_SIZE, DMA_FROM_DEVICE);
 		if (dma_mapping_error(dev, dma_addr))
 			break;
-		set_page_private(pages[i], dma_addr);
+		dma_addrs[i] = dma_addr;
 		dma_sync_single_for_device(dev, dma_addr, PAGE_SIZE, DMA_FROM_DEVICE);
 	}
 	if (i < AR_BUFFERS) {
-		while (i-- > 0) {
-			dma_addr_t dma_addr = page_private(pages[i]);
-			dma_unmap_page(dev, dma_addr, PAGE_SIZE, DMA_FROM_DEVICE);
-		}
+		while (i-- > 0)
+			dma_unmap_page(dev, dma_addrs[i], PAGE_SIZE, DMA_FROM_DEVICE);
 		vunmap(vaddr);
 		release_pages(pages, nr_populated);
 		return -ENOMEM;
 	}
 
+	memcpy(ctx->dma_addrs, dma_addrs, sizeof(ctx->dma_addrs));
 	ctx->buffer = vaddr;
 	memcpy(ctx->pages, pages, sizeof(ctx->pages));
 
@@ -910,7 +903,7 @@ static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
 		d->control        = cpu_to_le16(DESCRIPTOR_INPUT_MORE |
 						DESCRIPTOR_STATUS |
 						DESCRIPTOR_BRANCH_ALWAYS);
-		d->data_address   = cpu_to_le32(ar_buffer_bus(ctx, i));
+		d->data_address   = cpu_to_le32(ctx->dma_addrs[i]);
 		d->branch_address = cpu_to_le32(ctx->descriptors_bus +
 			ar_next_buffer_index(i) * sizeof(struct descriptor));
 	}
-- 
2.51.0