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[RFC,1/2] net: netlink: add nla_get_*_default() accessors

Message ID 20241024131807.0a6c07355832.I3df6aac71d38a5baa1c0a03d0c7e82d4395c030e@changeid (mailing list archive)
State RFC
Delegated to: Netdev Maintainers
Headers show
Series [RFC,1/2] net: netlink: add nla_get_*_default() accessors | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply

Commit Message

Johannes Berg Oct. 24, 2024, 11:18 a.m. UTC
From: Johannes Berg <johannes.berg@intel.com>

There are quite a number of places that use patterns
such as

  if (attr)
     val = nla_get_u16(attr);
  else
     val = DEFAULT;

Add nla_get_u16_default() and friends like that to
not have to type this out all the time.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/net/netlink.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

Comments

Johannes Berg Oct. 24, 2024, 11:29 a.m. UTC | #1
On Thu, 2024-10-24 at 13:18 +0200, Johannes Berg wrote:
> 
> +MAKE_NLA_GET_DEFAULT(u8, nla_get_u8);
> +MAKE_NLA_GET_DEFAULT(u16, nla_get_u16);
> +MAKE_NLA_GET_DEFAULT(u32, nla_get_u32);
> +MAKE_NLA_GET_DEFAULT(u64, nla_get_u64);
> +MAKE_NLA_GET_DEFAULT(unsigned long, nla_get_msecs);
> +MAKE_NLA_GET_DEFAULT(s8, nla_get_s8);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_s16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_s32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_s64);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_le16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_le32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_le64);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_be16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_be32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_be64);
> 

I obviously messed that up completely, but you get the point ...

johannes
Toke Høiland-Jørgensen Oct. 24, 2024, 12:51 p.m. UTC | #2
Johannes Berg <johannes@sipsolutions.net> writes:

> From: Johannes Berg <johannes.berg@intel.com>
>
> There are quite a number of places that use patterns
> such as
>
>   if (attr)
>      val = nla_get_u16(attr);
>   else
>      val = DEFAULT;
>
> Add nla_get_u16_default() and friends like that to
> not have to type this out all the time.
>
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>

I think this is an excellent idea! So typos/copy-paste errors aside:

Acked-by: Toke Høiland-Jørgensen <toke@kernel.org>
Jakub Kicinski Oct. 29, 2024, 3:54 p.m. UTC | #3
On Thu, 24 Oct 2024 13:18:06 +0200 Johannes Berg wrote:
> +#define MAKE_NLA_GET_DEFAULT(tp, fn)			\
> +static inline tp fn##_default(const struct nlattr *nla,	\
> +			      tp defvalue)		\
> +{							\
> +	if (!nla)					\
> +		return defvalue;			\
> +	return n(nla);					\
> +}
> +
> +MAKE_NLA_GET_DEFAULT(u8, nla_get_u8);
> +MAKE_NLA_GET_DEFAULT(u16, nla_get_u16);
> +MAKE_NLA_GET_DEFAULT(u32, nla_get_u32);
> +MAKE_NLA_GET_DEFAULT(u64, nla_get_u64);
> +MAKE_NLA_GET_DEFAULT(unsigned long, nla_get_msecs);
> +MAKE_NLA_GET_DEFAULT(s8, nla_get_s8);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_s16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_s32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_s64);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_le16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_le32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_le64);
> +MAKE_NLA_GET_DEFAULT(s16, nla_get_be16);
> +MAKE_NLA_GET_DEFAULT(s32, nla_get_be32);
> +MAKE_NLA_GET_DEFAULT(s64, nla_get_be64);

I'd vote to just spell out the accessors instead of hinding 
the definitions behind macros. Place them right after the
existing nla_get_* definition to make it more likely people
will notice them.

Either way:

Acked-by: Jakub Kicinski <kuba@kernel.org>
diff mbox series

Patch

diff --git a/include/net/netlink.h b/include/net/netlink.h
index db6af207287c..b15bd0437945 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -142,6 +142,8 @@ 
  *   nla_get_flag(nla)			return 1 if flag is true
  *   nla_get_msecs(nla)			get payload for a msecs attribute
  *
+ *   The same functions also exist with _default().
+ *
  * Attribute Misc:
  *   nla_memcpy(dest, nla, count)	copy attribute into memory
  *   nla_memcmp(nla, data, size)	compare attribute with memory area
@@ -1867,6 +1869,31 @@  static inline unsigned long nla_get_msecs(const struct nlattr *nla)
 	return msecs_to_jiffies((unsigned long) msecs);
 }
 
+#define MAKE_NLA_GET_DEFAULT(tp, fn)			\
+static inline tp fn##_default(const struct nlattr *nla,	\
+			      tp defvalue)		\
+{							\
+	if (!nla)					\
+		return defvalue;			\
+	return n(nla);					\
+}
+
+MAKE_NLA_GET_DEFAULT(u8, nla_get_u8);
+MAKE_NLA_GET_DEFAULT(u16, nla_get_u16);
+MAKE_NLA_GET_DEFAULT(u32, nla_get_u32);
+MAKE_NLA_GET_DEFAULT(u64, nla_get_u64);
+MAKE_NLA_GET_DEFAULT(unsigned long, nla_get_msecs);
+MAKE_NLA_GET_DEFAULT(s8, nla_get_s8);
+MAKE_NLA_GET_DEFAULT(s16, nla_get_s16);
+MAKE_NLA_GET_DEFAULT(s32, nla_get_s32);
+MAKE_NLA_GET_DEFAULT(s64, nla_get_s64);
+MAKE_NLA_GET_DEFAULT(s16, nla_get_le16);
+MAKE_NLA_GET_DEFAULT(s32, nla_get_le32);
+MAKE_NLA_GET_DEFAULT(s64, nla_get_le64);
+MAKE_NLA_GET_DEFAULT(s16, nla_get_be16);
+MAKE_NLA_GET_DEFAULT(s32, nla_get_be32);
+MAKE_NLA_GET_DEFAULT(s64, nla_get_be64);
+
 /**
  * nla_get_in_addr - return payload of IPv4 address attribute
  * @nla: IPv4 address netlink attribute