Re: [PATCH v3 -next 4/4] net: emaclite: Fix restricted cast warning of sparse

From: Andrew Lunn
Date: Fri Jan 31 2020 - 08:48:55 EST


On Fri, Jan 31, 2020 at 05:17:50PM +0530, Radhey Shyam Pandey wrote:
> Explicitly cast xemaclite_readl return value when it's passed to ntohl.
> Fixes below reported sparse warnings:
>
> xilinx_emaclite.c:411:24: sparse: sparse: cast to restricted __be32
> xilinx_emaclite.c:420:36: sparse: sparse: cast to restricted __be32
>
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> ---
> drivers/net/ethernet/xilinx/xilinx_emaclite.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> index 96e9d21..3273d4f 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> @@ -408,7 +408,8 @@ static u16 xemaclite_recv_data(struct net_local *drvdata, u8 *data, int maxlen)
>
> /* Get the protocol type of the ethernet frame that arrived
> */
> - proto_type = ((ntohl(xemaclite_readl(addr + XEL_HEADER_OFFSET +
> + proto_type = ((ntohl((__force __be32)xemaclite_readl(addr +
> + XEL_HEADER_OFFSET +
> XEL_RXBUFF_OFFSET)) >> XEL_HEADER_SHIFT) &
> XEL_RPLR_LENGTH_MASK);
>
> @@ -417,7 +418,7 @@ static u16 xemaclite_recv_data(struct net_local *drvdata, u8 *data, int maxlen)
> */
> if (proto_type > ETH_DATA_LEN) {
> if (proto_type == ETH_P_IP) {
> - length = ((ntohl(xemaclite_readl(addr +
> + length = ((ntohl((__force __be32)xemaclite_readl(addr +
> XEL_HEADER_IP_LENGTH_OFFSET +
> XEL_RXBUFF_OFFSET)) >>
> XEL_HEADER_SHIFT) &

If i understand this code correctly, you need the ntohl because you
are poking around inside the packet. All the other uses of
xemaclite_readl() are for descriptors etc.

It would be cleaner if you defined a xemaclite_readlbe32. If you use
ioread32be() it will do the endinness swap for you, so you don't need
the ntohl() and the horrible cast.

Andrew