[PATCH net-next v2 1/3] tools: ynl-gen: support sub-type for binary attributes

[Jakub Kicinski <kuba@kernel.org>]

Sub-type annotation on binary attributes may indicate that the attribute
carries an array of simple types (also referred to as "C array" in docs).
Support rendering them as such in the C user code. For example for u32,
instead of:

  struct {
    u32 arr;
  } _len;

  void *arr;

render:

  struct {
    u32 arr;
  } _count;

  __u32 *arr;

Note that count is the number of elements while len was the length in bytes.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - create a separate class
v1: https://lore.kernel.org/20250508022839.1256059-2-kuba@kernel.org/
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 43 +++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index 4a2d3cc07e14..4e2ae738c0aa 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py
@@ -163,7 +163,7 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
         return False
 
     def _free_lines(self, ri, var, ref):
-        if self.is_multi_val() or self.presence_type() == 'len':
+        if self.is_multi_val() or self.presence_type() in {'count', 'len'}:
             return [f'free({var}->{ref}{self.c_name});']
         return []
 
@@ -566,6 +566,40 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
                 f'memcpy({member}, {self.c_name}, {presence});']
 
 
+class TypeBinaryScalarArray(TypeBinary):
+    def arg_member(self, ri):
+        return [f'__{self.get("sub-type")} *{self.c_name}', 'size_t count']
+
+    def presence_type(self):
+        return 'count'
+
+    def struct_member(self, ri):
+        ri.cw.p(f'__{self.get("sub-type")} *{self.c_name};')
+
+    def attr_put(self, ri, var):
+        presence = self.presence_type()
+        ri.cw.block_start(line=f"if ({var}->_{presence}.{self.c_name})")
+        ri.cw.p(f"i = {var}->_{presence}.{self.c_name} * sizeof(__{self.get('sub-type')});")
+        ri.cw.p(f"ynl_attr_put(nlh, {self.enum_name}, " +
+                f"{var}->{self.c_name}, i);")
+        ri.cw.block_end()
+
+    def _attr_get(self, ri, var):
+        len_mem = var + '->_count.' + self.c_name
+        return [f"{len_mem} = len / sizeof(__{self.get('sub-type')});",
+                f"len = {len_mem} * sizeof(__{self.get('sub-type')});",
+                f"{var}->{self.c_name} = malloc(len);",
+                f"memcpy({var}->{self.c_name}, ynl_attr_data(attr), len);"], \
+               ['len = ynl_attr_data_len(attr);'], \
+               ['unsigned int len;']
+
+    def _setter_lines(self, ri, member, presence):
+        return [f"{presence} = count;",
+                f"count *= sizeof(__{self.get('sub-type')});",
+                f"{member} = malloc(count);",
+                f'memcpy({member}, {self.c_name}, count);']
+
+
 class TypeBitfield32(Type):
     def _complex_member_type(self, ri):
         return "struct nla_bitfield32"
@@ -672,7 +706,7 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
         lines = []
         if self.attr['type'] in scalars:
             lines += [f"free({var}->{ref}{self.c_name});"]
-        elif self.attr['type'] == 'binary' and 'struct' in self.attr:
+        elif self.attr['type'] == 'binary':
             lines += [f"free({var}->{ref}{self.c_name});"]
         elif self.attr['type'] == 'string':
             lines += [
@@ -976,7 +1010,10 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
         elif elem['type'] == 'string':
             t = TypeString(self.family, self, elem, value)
         elif elem['type'] == 'binary':
-            t = TypeBinary(self.family, self, elem, value)
+            if elem.get('sub-type') in scalars:
+                t = TypeBinaryScalarArray(self.family, self, elem, value)
+            else:
+                t = TypeBinary(self.family, self, elem, value)
         elif elem['type'] == 'bitfield32':
             t = TypeBitfield32(self.family, self, elem, value)
         elif elem['type'] == 'nest':
-- 
2.49.0