| Message ID | 20210304223431.15045-3-elder@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: qualcomm: rmnet: stop using C bit-fields | expand |
On Thu 04 Mar 16:34 CST 2021, Alex Elder wrote: > In rmnet_map_ipv4_ul_csum_header() and rmnet_map_ipv6_ul_csum_header() > the offset within a packet at which checksumming should commence is > calculated. This calculation involves byte swapping and a forced type > conversion that makes it hard to understand. > > Simplify this by computing the offset in host byte order, then > converting the result when assigning it into the header field. > > Signed-off-by: Alex Elder <elder@linaro.org> > --- > .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 22 ++++++++++--------- > 1 file changed, 12 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c > index 21d38167f9618..bd1aa11c9ce59 100644 > --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c > +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c > @@ -197,12 +197,13 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr, > struct rmnet_map_ul_csum_header *ul_header, > struct sk_buff *skb) > { > - struct iphdr *ip4h = (struct iphdr *)iphdr; > - __be16 *hdr = (__be16 *)ul_header, offset; > + __be16 *hdr = (__be16 *)ul_header; > + struct iphdr *ip4h = iphdr; > + u16 offset; > + > + offset = skb_transport_header(skb) - (unsigned char *)iphdr; > + ul_header->csum_start_offset = htons(offset); > > - offset = htons((__force u16)(skb_transport_header(skb) - Just curious, why does this require a __force, or even a cast? Regardless, your proposed way of writing it is easier to read. Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> Regards, Bjorn > - (unsigned char *)iphdr)); > - ul_header->csum_start_offset = offset; > ul_header->csum_insert_offset = skb->csum_offset; > ul_header->csum_enabled = 1; > if (ip4h->protocol == IPPROTO_UDP) > @@ -239,12 +240,13 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr, > struct rmnet_map_ul_csum_header *ul_header, > struct sk_buff *skb) > { > - struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr; > - __be16 *hdr = (__be16 *)ul_header, offset; > + __be16 *hdr = (__be16 *)ul_header; > + struct ipv6hdr *ip6h = ip6hdr; > + u16 offset; > + > + offset = skb_transport_header(skb) - (unsigned char *)ip6hdr; > + ul_header->csum_start_offset = htons(offset); > > - offset = htons((__force u16)(skb_transport_header(skb) - > - (unsigned char *)ip6hdr)); > - ul_header->csum_start_offset = offset; > ul_header->csum_insert_offset = skb->csum_offset; > ul_header->csum_enabled = 1; > > -- > 2.20.1 >
On 3/4/21 10:07 PM, Bjorn Andersson wrote: > On Thu 04 Mar 16:34 CST 2021, Alex Elder wrote: > >> In rmnet_map_ipv4_ul_csum_header() and rmnet_map_ipv6_ul_csum_header() >> the offset within a packet at which checksumming should commence is >> calculated. This calculation involves byte swapping and a forced type >> conversion that makes it hard to understand. >> >> Simplify this by computing the offset in host byte order, then >> converting the result when assigning it into the header field. >> >> Signed-off-by: Alex Elder <elder@linaro.org> >> --- >> .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 22 ++++++++++--------- >> 1 file changed, 12 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> index 21d38167f9618..bd1aa11c9ce59 100644 >> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> @@ -197,12 +197,13 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr, >> struct rmnet_map_ul_csum_header *ul_header, >> struct sk_buff *skb) >> { >> - struct iphdr *ip4h = (struct iphdr *)iphdr; >> - __be16 *hdr = (__be16 *)ul_header, offset; >> + __be16 *hdr = (__be16 *)ul_header; >> + struct iphdr *ip4h = iphdr; >> + u16 offset; >> + >> + offset = skb_transport_header(skb) - (unsigned char *)iphdr; >> + ul_header->csum_start_offset = htons(offset); >> >> - offset = htons((__force u16)(skb_transport_header(skb) - > > Just curious, why does this require a __force, or even a cast? The argument to htons() has type __u16. In this case it is passed the difference between pointers, which will have type ptrdiff_t, which is certainly bigger than 16 bits. I don't think the __force is needed, but the cast to u16 might just be making the conversion to the smaller type explicit. Here too though, I don't think it's necessary. -Alex > Regardless, your proposed way of writing it is easier to read. > > Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> > > Regards, > Bjorn > >> - (unsigned char *)iphdr)); >> - ul_header->csum_start_offset = offset; >> ul_header->csum_insert_offset = skb->csum_offset; >> ul_header->csum_enabled = 1; >> if (ip4h->protocol == IPPROTO_UDP) >> @@ -239,12 +240,13 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr, >> struct rmnet_map_ul_csum_header *ul_header, >> struct sk_buff *skb) >> { >> - struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr; >> - __be16 *hdr = (__be16 *)ul_header, offset; >> + __be16 *hdr = (__be16 *)ul_header; >> + struct ipv6hdr *ip6h = ip6hdr; >> + u16 offset; >> + >> + offset = skb_transport_header(skb) - (unsigned char *)ip6hdr; >> + ul_header->csum_start_offset = htons(offset); >> >> - offset = htons((__force u16)(skb_transport_header(skb) - >> - (unsigned char *)ip6hdr)); >> - ul_header->csum_start_offset = offset; >> ul_header->csum_insert_offset = skb->csum_offset; >> ul_header->csum_enabled = 1; >> >> -- >> 2.20.1 >>
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c index 21d38167f9618..bd1aa11c9ce59 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c @@ -197,12 +197,13 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr, struct rmnet_map_ul_csum_header *ul_header, struct sk_buff *skb) { - struct iphdr *ip4h = (struct iphdr *)iphdr; - __be16 *hdr = (__be16 *)ul_header, offset; + __be16 *hdr = (__be16 *)ul_header; + struct iphdr *ip4h = iphdr; + u16 offset; + + offset = skb_transport_header(skb) - (unsigned char *)iphdr; + ul_header->csum_start_offset = htons(offset); - offset = htons((__force u16)(skb_transport_header(skb) - - (unsigned char *)iphdr)); - ul_header->csum_start_offset = offset; ul_header->csum_insert_offset = skb->csum_offset; ul_header->csum_enabled = 1; if (ip4h->protocol == IPPROTO_UDP) @@ -239,12 +240,13 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr, struct rmnet_map_ul_csum_header *ul_header, struct sk_buff *skb) { - struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr; - __be16 *hdr = (__be16 *)ul_header, offset; + __be16 *hdr = (__be16 *)ul_header; + struct ipv6hdr *ip6h = ip6hdr; + u16 offset; + + offset = skb_transport_header(skb) - (unsigned char *)ip6hdr; + ul_header->csum_start_offset = htons(offset); - offset = htons((__force u16)(skb_transport_header(skb) - - (unsigned char *)ip6hdr)); - ul_header->csum_start_offset = offset; ul_header->csum_insert_offset = skb->csum_offset; ul_header->csum_enabled = 1;
In rmnet_map_ipv4_ul_csum_header() and rmnet_map_ipv6_ul_csum_header() the offset within a packet at which checksumming should commence is calculated. This calculation involves byte swapping and a forced type conversion that makes it hard to understand. Simplify this by computing the offset in host byte order, then converting the result when assigning it into the header field. Signed-off-by: Alex Elder <elder@linaro.org> --- .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 22 ++++++++++--------- 1 file changed, 12 insertions(+), 10 deletions(-) -- 2.20.1