Subject: Re: [PATCH v2 2/3] net: thunderbolt: Fix sparse warnings in tbnet_xmit_csum_and_map()

From: Simon Horman <[email-masked]>
Date: Tue, 11 Apr 2023 13:50:16 +0200

On Tue, Apr 11, 2023 at 12:10:48PM +0300, Mika Westerberg wrote:
> Fixes the following warning when the driver is built with sparse checks
> enabled:
> 
> main.c:993:23: warning: incorrect type in initializer (different base types)
> main.c:993:23:    expected restricted __wsum [usertype] wsum
> main.c:993:23:    got restricted __be32 [usertype]
> 
> No functional changes intended.

This seems nice.

After you posted v1 I was wondering if, as a follow-up, it would be worth
creating a helper for this, say cpu_to_wsum(), as I think this pattern
occurs a few times. I'm thinking of a trivial wrapper around cpu_to_be32().

> 
> Signed-off-by: Mika Westerberg <[email-masked]>
> Reviewed-by: Simon Horman <[email-masked]>
> Reviewed-by: Andy Shevchenko <[email-masked]>
> ---
>  drivers/net/thunderbolt/main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
> index 27f8573a2b6e..6a43ced74881 100644
> --- a/drivers/net/thunderbolt/main.c
> +++ b/drivers/net/thunderbolt/main.c
> @@ -991,8 +991,10 @@ static bool tbnet_xmit_csum_and_map(struct tbnet *net, struct sk_buff *skb,
>  {
>  	struct thunderbolt_ip_frame_header *hdr = page_address(frames[0]->page);
>  	struct device *dma_dev = tb_ring_dma_device(net->tx_ring.ring);
> -	__wsum wsum = htonl(skb->len - skb_transport_offset(skb));
>  	unsigned int i, len, offset = skb_transport_offset(skb);
> +	/* Remove payload length from checksum */
> +	u32 paylen = skb->len - skb_transport_offset(skb);
> +	__wsum wsum = (__force __wsum)htonl(paylen);
>  	__be16 protocol = skb->protocol;
>  	void *data = skb->data;
>  	void *dest = hdr + 1;
> -- 
> 2.39.2
>