Re: [PATCH v3] batman-adv: Add flex array to struct batadv_tvlv_tt_data

Hi Sven,

On Sat, May 04, 2024 at 11:35:38AM +0200, Sven Eckelmann wrote:

On Wednesday, 1 May 2024 17:02:42 CEST Erick Archer wrote:

quoted

diff --git a/include/uapi/linux/batadv_packet.h b/include/uapi/linux/batadv_packet.h
index 6e25753015df..dfbe30536995 100644
--- a/include/uapi/linux/batadv_packet.h
+++ b/include/uapi/linux/batadv_packet.h

[...]

quoted

+/**
+ * struct batadv_tvlv_tt_data - tt data propagated through the tt tvlv container
+ * @flags: translation table flags (see batadv_tt_data_flags)
+ * @ttvn: translation table version number
+ * @num_vlan: number of announced VLANs. In the TVLV this struct is followed by
+ *  one batadv_tvlv_tt_vlan_data object per announced vlan
+ * @vlan_data: array of batadv_tvlv_tt_vlan_data objects
+ */
+struct batadv_tvlv_tt_data {
+       __u8   flags;
+       __u8   ttvn;
+       __be16 num_vlan;
+       struct batadv_tvlv_tt_vlan_data vlan_data[] __counted_by_be(num_vlan);
+};

Thanks for the updates. But I can't accept this at the moment because 
__counted_by_be is used in an uapi header without it being defined
include/uapi/linux/stddef.h (and this file is also not included in this 
header).

See commit c8248faf3ca2 ("Compiler Attributes: counted_by: Adjust name and 
identifier expansion") as an example for the similar __counted_by macro.

If I understand correctly, the following changes are also needed because
the annotated struct is defined in a "uapi" header. Sorry if it's a stupid
question, but I'm new to these topics.

diff --git a/include/uapi/linux/batadv_packet.h b/include/uapi/linux/batadv_packet.h
index 6e25753015df..41f39d7661c9 100644
--- a/include/uapi/linux/batadv_packet.h
+++ b/include/uapi/linux/batadv_packet.h

@@ -9,6 +9,7 @@

 #include <asm/byteorder.h>
 #include <linux/if_ether.h>
+#include <linux/stddef.h>
 #include <linux/types.h>

 /**

diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h
index 2ec6f35cda32..58154117d9b0 100644
--- a/include/uapi/linux/stddef.h
+++ b/include/uapi/linux/stddef.h

@@ -55,4 +55,12 @@
 #define __counted_by(m)
 #endif

+#ifndef __counted_by_le
+#define __counted_by_le(m)
+#endif
+
+#ifndef __counted_by_be
+#define __counted_by_be(m)
+#endif
+
 #endif /* _UAPI_LINUX_STDDEF_H */

If this is the right path, can these changes be merged into a
single patch or is it better to add a previous patch to define
__counted_by{le,be}?

Regards,
Erick

Kind regards,
	Sven