dma_map_XXX() functions return values DMA_MAPPING_ERROR as error values
which is often ~0.  The error value should be tested with
dma_mapping_error().

This patch creates a new function in niu_ops to test if the mapping
failed.  The test is fixed in niu_rbr_add_page(), added in
niu_start_xmit() and the successfully mapped pages are unmaped upon error.

Fixes: ec2deec1f352 ("niu: Fix to check for dma mapping errors.")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
---
 drivers/net/ethernet/sun/niu.c | 31 ++++++++++++++++++++++++++++++-
 drivers/net/ethernet/sun/niu.h |  4 ++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sun/niu.c b/drivers/net/ethernet/sun/niu.c
index ddca8fc7883e..26119d02a94d 100644
--- a/drivers/net/ethernet/sun/niu.c
+++ b/drivers/net/ethernet/sun/niu.c
@@ -3336,7 +3336,7 @@ static int niu_rbr_add_page(struct niu *np, struct rx_ring_info *rp,
 
 	addr = np->ops->map_page(np->device, page, 0,
 				 PAGE_SIZE, DMA_FROM_DEVICE);
-	if (!addr) {
+	if (np->ops->mapping_error(np->device, addr)) {
 		__free_page(page);
 		return -ENOMEM;
 	}
@@ -6676,6 +6676,8 @@ static netdev_tx_t niu_start_xmit(struct sk_buff *skb,
 	len = skb_headlen(skb);
 	mapping = np->ops->map_single(np->device, skb->data,
 				      len, DMA_TO_DEVICE);
+	if (np->ops->mapping_error(np->device, mapping))
+		goto out_drop;
 
 	prod = rp->prod;
 
@@ -6717,6 +6719,8 @@ static netdev_tx_t niu_start_xmit(struct sk_buff *skb,
 		mapping = np->ops->map_page(np->device, skb_frag_page(frag),
 					    skb_frag_off(frag), len,
 					    DMA_TO_DEVICE);
+		if (np->ops->mapping_error(np->device, mapping))
+			goto out_unmap;
 
 		rp->tx_buffs[prod].skb = NULL;
 		rp->tx_buffs[prod].mapping = mapping;
@@ -6741,6 +6745,19 @@ static netdev_tx_t niu_start_xmit(struct sk_buff *skb,
 out:
 	return NETDEV_TX_OK;
 
+out_unmap:
+	while (i--) {
+		const skb_frag_t *frag;
+
+		prod = PREVIOUS_TX(rp, prod);
+		frag = &skb_shinfo(skb)->frags[i];
+		np->ops->unmap_page(np->device, rp->tx_buffs[prod].mapping,
+				    skb_frag_size(frag), DMA_TO_DEVICE);
+	}
+
+	np->ops->unmap_single(np->device, rp->tx_buffs[rp->prod].mapping,
+			      skb_headlen(skb), DMA_TO_DEVICE);
+
 out_drop:
 	rp->tx_errors++;
 	kfree_skb(skb);
@@ -9644,6 +9661,11 @@ static void niu_pci_unmap_single(struct device *dev, u64 dma_address,
 	dma_unmap_single(dev, dma_address, size, direction);
 }
 
+static int niu_pci_mapping_error(struct device *dev, u64 addr)
+{
+	return dma_mapping_error(dev, addr);
+}
+
 static const struct niu_ops niu_pci_ops = {
 	.alloc_coherent	= niu_pci_alloc_coherent,
 	.free_coherent	= niu_pci_free_coherent,
@@ -9651,6 +9673,7 @@ static const struct niu_ops niu_pci_ops = {
 	.unmap_page	= niu_pci_unmap_page,
 	.map_single	= niu_pci_map_single,
 	.unmap_single	= niu_pci_unmap_single,
+	.mapping_error	= niu_pci_mapping_error,
 };
 
 static void niu_driver_version(void)
@@ -10019,6 +10042,11 @@ static void niu_phys_unmap_single(struct device *dev, u64 dma_address,
 	/* Nothing to do.  */
 }
 
+static int niu_phys_mapping_error(struct device *dev, u64 dma_address)
+{
+	return false;
+}
+
 static const struct niu_ops niu_phys_ops = {
 	.alloc_coherent	= niu_phys_alloc_coherent,
 	.free_coherent	= niu_phys_free_coherent,
@@ -10026,6 +10054,7 @@ static const struct niu_ops niu_phys_ops = {
 	.unmap_page	= niu_phys_unmap_page,
 	.map_single	= niu_phys_map_single,
 	.unmap_single	= niu_phys_unmap_single,
+	.mapping_error	= niu_phys_mapping_error,
 };
 
 static int niu_of_probe(struct platform_device *op)
diff --git a/drivers/net/ethernet/sun/niu.h b/drivers/net/ethernet/sun/niu.h
index 04c215f91fc0..0b169c08b0f2 100644
--- a/drivers/net/ethernet/sun/niu.h
+++ b/drivers/net/ethernet/sun/niu.h
@@ -2879,6 +2879,9 @@ struct tx_ring_info {
 #define NEXT_TX(tp, index) \
 	(((index) + 1) < (tp)->pending ? ((index) + 1) : 0)
 
+#define PREVIOUS_TX(tp, index) \
+	(((index) - 1) >= 0 ? ((index) - 1) : (((tp)->pending) - 1))
+
 static inline u32 niu_tx_avail(struct tx_ring_info *tp)
 {
 	return (tp->pending -
@@ -3140,6 +3143,7 @@ struct niu_ops {
 			  enum dma_data_direction direction);
 	void (*unmap_single)(struct device *dev, u64 dma_address,
 			     size_t size, enum dma_data_direction direction);
+	int (*mapping_error)(struct device *dev, u64 dma_address);
 };
 
 struct niu_link_config {
-- 
2.43.0

On Mon, Jun 30, 2025 at 10:36:43AM +0200, Thomas Fourier wrote:
> dma_map_XXX() functions return values DMA_MAPPING_ERROR as error values
> which is often ~0.  The error value should be tested with
> dma_mapping_error().
> 
> This patch creates a new function in niu_ops to test if the mapping
> failed.  The test is fixed in niu_rbr_add_page(), added in
> niu_start_xmit() and the successfully mapped pages are unmaped upon error.
> 
> Fixes: ec2deec1f352 ("niu: Fix to check for dma mapping errors.")

I think it fixes a bit more than that.
But perhaps the above tag is sufficient.

> Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>

Overall this looks good to me, thanks for the update.

Reviewed-by: Simon Horman <horms@kernel.org>

> ---
>  drivers/net/ethernet/sun/niu.c | 31 ++++++++++++++++++++++++++++++-
>  drivers/net/ethernet/sun/niu.h |  4 ++++
>  2 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/sun/niu.c b/drivers/net/ethernet/sun/niu.c

...

> @@ -10019,6 +10042,11 @@ static void niu_phys_unmap_single(struct device *dev, u64 dma_address,
>  	/* Nothing to do.  */
>  }
>  
> +static int niu_phys_mapping_error(struct device *dev, u64 dma_address)
> +{
> +	return false;

No need to resend just because of this, but
from a type PoV this should probably be:

	return 0;

> +}
> +
>  static const struct niu_ops niu_phys_ops = {
>  	.alloc_coherent	= niu_phys_alloc_coherent,
>  	.free_coherent	= niu_phys_free_coherent,

...