Re: [PATCH] net: stmmac: use dma_addr_t for DMA addresses

[Maxime Chevallier]

Hi Alex,

On 8/11/26 21:27, Alex Elder wrote:
> In jumbo_frm() (implemented in both "chain_mode.c" and "ring_mode.c"),
> an unsigned integer local variable is used to hold the value returned
> by dma_map_single().  On systems where a dma_addr_t is 64 bits, the
> subsequent dma_mapping_error() check of the returned value operates
> only on the low 32 bits (whose high bit won't be sign-extended).  In
> this case, dma_mapping_error() would return 0 (no error) even if there
> were one.
> 
> Fix this in both spots by using a dma_addr_t for the local variable.

Thanks :)

I was wondering if it would silently hides another address size related
issue a little bit lower, as we now have :

  dma_addr_t des2;

  des2 = dma_map_single(...);

  desc->des2 = cpu_to_le32(des2);

desc->des2 is __le32, so for 64 bit addresses we silently truncate the
address.

However I don't see how jumbo would work on 64-bits anyways as des3 is the next
chunk of the jumbo frame...

I think this is good as-is, so

Reviewed-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>

Maxime

> 
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Link: https://lore.kernel.org/linux-devicetree/20260606010122.21A211F00899@xxxxxxxxxxxxxxx/
> Signed-off-by: Alex Elder <elder@xxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/stmicro/stmmac/chain_mode.c | 3 ++-
>  drivers/net/ethernet/stmicro/stmmac/ring_mode.c  | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> index fc04a23342cfc..ec25193d287bb 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> @@ -20,9 +20,10 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb,
>  	unsigned int nopaged_len = skb_headlen(skb);
>  	struct stmmac_priv *priv = tx_q->priv_data;
>  	unsigned int entry = tx_q->cur_tx;
> -	unsigned int bmax, buf_len, des2;
> +	unsigned int bmax, buf_len;
>  	unsigned int i = 1, len;
>  	struct dma_desc *desc;
> +	dma_addr_t des2;
>  
>  	desc = tx_q->dma_tx + entry;
>  
> diff --git a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
> index 78fc6aa5bbe95..664d8cfb58cdc 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
> @@ -20,8 +20,9 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb,
>  	unsigned int nopaged_len = skb_headlen(skb);
>  	struct stmmac_priv *priv = tx_q->priv_data;
>  	unsigned int entry = tx_q->cur_tx;
> -	unsigned int bmax, len, des2;
> +	unsigned int bmax, len;
>  	struct dma_desc *desc;
> +	dma_addr_t des2;
>  
>  	if (priv->extend_desc)
>  		desc = (struct dma_desc *)(tx_q->dma_etx + entry);
> 
> base-commit: 31397cf1819210bd63fa3d2c7d8c24f7c8667d99