On Mon, Dec 23, 2019 at 08:08:55PM -0800, Florian Fainelli wrote:

On 12/22/2019 3:45 PM, Michal Kubecek wrote:

quoted

Add common request/reply header definition and helpers to parse request
header and fill reply header. Provide ethnl_update_* helpers to update
structure members from request attributes (to be used for *_SET requests).

Signed-off-by: Michal Kubecek <redacted>
---

[snip]

quoted

+/**
+ * ethnl_update_u32() - update u32 value from NLA_U32 attribute
+ * @dst:  value to update
+ * @attr: netlink attribute with new value or null
+ * @mod:  pointer to bool for modification tracking
+ *
+ * Copy the u32 value from NLA_U32 netlink attribute @attr into variable
+ * pointed to by @dst; do nothing if @attr is null. Bool pointed to by @mod
+ * is set to true if this function changed the value of *dst, otherwise it
+ * is left as is.
+ */

I would find it more intuitive if an integer was returned: < 0 in case
of error, 0 if no change and 1 if something changed.

This trick allows simpler code on caller side when we update multiple
values in a structure - we don't have to check each return value
separately (most update helpers cannot fail). It was a suggestion from
Jiri Pirko in one of earlier discussions.
 

quoted

+static inline void ethnl_update_u32(u32 *dst, const struct nlattr *attr,
+				    bool *mod)
+{
+	u32 val;
+
+	if (!attr)
+		return;
+	val = nla_get_u32(attr);
+	if (*dst == val)
+		return;
+
+	*dst = val;
+	*mod = true;
+}
+
+/**
+ * ethnl_update_u8() - update u8 value from NLA_U8 attribute
+ * @dst:  value to update
+ * @attr: netlink attribute with new value or null
+ * @mod:  pointer to bool for modification tracking
+ *
+ * Copy the u8 value from NLA_U8 netlink attribute @attr into variable
+ * pointed to by @dst; do nothing if @attr is null. Bool pointed to by @mod
+ * is set to true if this function changed the value of *dst, otherwise it
+ * is left as is.
+ */
+static inline void ethnl_update_u8(u8 *dst, const struct nlattr *attr,
+				   bool *mod)
+{
+	u8 val;
+
+	if (!attr)
+		return;
+	val = nla_get_u32(attr);

Should not this be nla_get_u8() here? This sounds like it is going to
break on BE machines.

Good catch, thank you. I originally wanted to use NLA_U32 for all
numeric values (as NLA_U8 and NLA_U16 don't save any space anyway) but
then changed those in LINKINFO_GET request to NLA_U8 and forgot to fix
the helper function.

I'll fix this in v9.

Michal