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[PATCH] libfdt: Replace hardcoded FDT version numbers with macros

  • To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>
  • Date: Thu, 13 Nov 2025 10:36:16 +0000
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  • Cc: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
  • Delivery-date: Thu, 13 Nov 2025 10:36:31 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHcVIlX6FmSxVBd8UyRU/9awRURXA==
  • Thread-topic: [PATCH] libfdt: Replace hardcoded FDT version numbers with macros
Replace all hardcoded FDT version numbers (such as 16 and 17, or 0x10 and 0x11)
with the macros FDT_LAST_COMPATIBLE_VERSION and FDT_LAST_SUPPORTED_VERSION
throughout the Xen device tree and libfdt code.

This avoids magic numbers and makes the Xen codebase more robust to future FDT
version changes.

Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
---
 xen/common/device-tree/device-tree.c |  2 +-
 xen/common/libfdt/fdt.c              |  8 +++++---
 xen/common/libfdt/fdt_ro.c           | 13 +++++++------
 xen/common/libfdt/fdt_rw.c           | 16 ++++++++--------
 4 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/xen/common/device-tree/device-tree.c 
b/xen/common/device-tree/device-tree.c
index 0b5375f151..ee8b32a8b4 100644
--- a/xen/common/device-tree/device-tree.c
+++ b/xen/common/device-tree/device-tree.c
@@ -1949,7 +1949,7 @@ static unsigned long unflatten_dt_node(const void *fdt,
         sz = be32_to_cpu(*(__be32 *)(*p));
         noff = be32_to_cpu(*(__be32 *)((*p) + 4));
         *p += 8;
-        if ( fdt_version(fdt) < 0x10 )
+        if ( fdt_version(fdt) < FDT_LAST_COMPATIBLE_VERSION )
             *p = ROUNDUP(*p, sz >= 8 ? 8 : 4);
 
         pname = fdt_string(fdt, noff);
diff --git a/xen/common/libfdt/fdt.c b/xen/common/libfdt/fdt.c
index 9fe7cf4b74..4b30a17b93 100644
--- a/xen/common/libfdt/fdt.c
+++ b/xen/common/libfdt/fdt.c
@@ -119,7 +119,8 @@ int fdt_check_header(const void *fdt)
 
        if (!can_assume(VALID_DTB)) {
                /* Bounds check structure block */
-               if (!can_assume(LATEST) && fdt_version(fdt) < 17) {
+               if (!can_assume(LATEST) &&
+                       fdt_version(fdt) < FDT_LAST_SUPPORTED_VERSION) {
                        if (!check_off_(hdrsize, fdt_totalsize(fdt),
                                        fdt_off_dt_struct(fdt)))
                                return -FDT_ERR_TRUNCATED;
@@ -154,7 +155,7 @@ const void *fdt_offset_ptr(const void *fdt, int offset, 
unsigned int len)
                    || (absoffset + len) > fdt_totalsize(fdt))
                        return NULL;
 
-       if (can_assume(LATEST) || fdt_version(fdt) >= 0x11)
+       if (can_assume(LATEST) || fdt_version(fdt) >= 
FDT_LAST_SUPPORTED_VERSION)
                if (((uoffset + len) < uoffset)
                    || ((offset + len) > fdt_size_dt_struct(fdt)))
                        return NULL;
@@ -195,7 +196,8 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int 
*nextoffset)
                offset += sizeof(struct fdt_property) - FDT_TAGSIZE
                        + fdt32_to_cpu(*lenp);
                if (!can_assume(LATEST) &&
-                   fdt_version(fdt) < 0x10 && fdt32_to_cpu(*lenp) >= 8 &&
+                   fdt_version(fdt) < FDT_LAST_COMPATIBLE_VERSION &&
+                   fdt32_to_cpu(*lenp) >= 8 &&
                    ((offset - fdt32_to_cpu(*lenp)) % 8) != 0)
                        offset += 4;
                break;
diff --git a/xen/common/libfdt/fdt_ro.c b/xen/common/libfdt/fdt_ro.c
index 17584da257..f719712b71 100644
--- a/xen/common/libfdt/fdt_ro.c
+++ b/xen/common/libfdt/fdt_ro.c
@@ -60,7 +60,8 @@ const char *fdt_get_string(const void *fdt, int stroffset, 
int *lenp)
        if (fdt_magic(fdt) == FDT_MAGIC) {
                if (stroffset < 0)
                        goto fail;
-               if (can_assume(LATEST) || fdt_version(fdt) >= 17) {
+               if (can_assume(LATEST) ||
+                       fdt_version(fdt) >= FDT_LAST_SUPPORTED_VERSION) {
                        if ((unsigned)stroffset >= fdt_size_dt_strings(fdt))
                                goto fail;
                        if ((fdt_size_dt_strings(fdt) - stroffset) < len)
@@ -309,7 +310,7 @@ const char *fdt_get_name(const void *fdt, int nodeoffset, 
int *len)
 
        nameptr = nh->name;
 
-       if (!can_assume(LATEST) && fdt_version(fdt) < 0x10) {
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_COMPATIBLE_VERSION) {
                /*
                 * For old FDT versions, match the naming conventions of V16:
                 * give only the leaf name (after all /). The actual tree
@@ -382,7 +383,7 @@ const struct fdt_property *fdt_get_property_by_offset(const 
void *fdt,
        /* Prior to version 16, properties may need realignment
         * and this API does not work. fdt_getprop_*() will, however. */
 
-       if (!can_assume(LATEST) && fdt_version(fdt) < 0x10) {
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_COMPATIBLE_VERSION) {
                if (lenp)
                        *lenp = -FDT_ERR_BADVERSION;
                return NULL;
@@ -429,7 +430,7 @@ const struct fdt_property *fdt_get_property_namelen(const 
void *fdt,
 {
        /* Prior to version 16, properties may need realignment
         * and this API does not work. fdt_getprop_*() will, however. */
-       if (!can_assume(LATEST) && fdt_version(fdt) < 0x10) {
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_COMPATIBLE_VERSION) {
                if (lenp)
                        *lenp = -FDT_ERR_BADVERSION;
                return NULL;
@@ -460,7 +461,7 @@ const void *fdt_getprop_namelen(const void *fdt, int 
nodeoffset,
                return NULL;
 
        /* Handle realignment */
-       if (!can_assume(LATEST) && fdt_version(fdt) < 0x10 &&
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_COMPATIBLE_VERSION &&
            (poffset + sizeof(*prop)) % 8 && fdt32_ld_(&prop->len) >= 8)
                return prop->data + 4;
        return prop->data;
@@ -493,7 +494,7 @@ const void *fdt_getprop_by_offset(const void *fdt, int 
offset,
        }
 
        /* Handle realignment */
-       if (!can_assume(LATEST) && fdt_version(fdt) < 0x10 &&
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_COMPATIBLE_VERSION &&
            (offset + sizeof(*prop)) % 8 && fdt32_ld_(&prop->len) >= 8)
                return prop->data + 4;
        return prop->data;
diff --git a/xen/common/libfdt/fdt_rw.c b/xen/common/libfdt/fdt_rw.c
index 3621d3651d..9e87eabc5d 100644
--- a/xen/common/libfdt/fdt_rw.c
+++ b/xen/common/libfdt/fdt_rw.c
@@ -28,13 +28,13 @@ static int fdt_rw_probe_(void *fdt)
                return 0;
        FDT_RO_PROBE(fdt);
 
-       if (!can_assume(LATEST) && fdt_version(fdt) < 17)
+       if (!can_assume(LATEST) && fdt_version(fdt) < 
FDT_LAST_SUPPORTED_VERSION)
                return -FDT_ERR_BADVERSION;
        if (fdt_blocks_misordered_(fdt, sizeof(struct fdt_reserve_entry),
                                   fdt_size_dt_struct(fdt)))
                return -FDT_ERR_BADLAYOUT;
-       if (!can_assume(LATEST) && fdt_version(fdt) > 17)
-               fdt_set_version(fdt, 17);
+       if (!can_assume(LATEST) && fdt_version(fdt) > 
FDT_LAST_SUPPORTED_VERSION)
+               fdt_set_version(fdt, FDT_LAST_SUPPORTED_VERSION);
 
        return 0;
 }
@@ -430,9 +430,9 @@ int fdt_open_into(const void *fdt, void *buf, int bufsize)
        mem_rsv_size = (fdt_num_mem_rsv(fdt)+1)
                * sizeof(struct fdt_reserve_entry);
 
-       if (can_assume(LATEST) || fdt_version(fdt) >= 17) {
+       if (can_assume(LATEST) || fdt_version(fdt) >= 
FDT_LAST_SUPPORTED_VERSION) {
                struct_size = fdt_size_dt_struct(fdt);
-       } else if (fdt_version(fdt) == 16) {
+       } else if (fdt_version(fdt) == FDT_LAST_COMPATIBLE_VERSION) {
                struct_size = 0;
                while (fdt_next_tag(fdt, struct_size, &struct_size) != FDT_END)
                        ;
@@ -448,7 +448,7 @@ int fdt_open_into(const void *fdt, void *buf, int bufsize)
                err = fdt_move(fdt, buf, bufsize);
                if (err)
                        return err;
-               fdt_set_version(buf, 17);
+               fdt_set_version(buf, FDT_LAST_SUPPORTED_VERSION);
                fdt_set_size_dt_struct(buf, struct_size);
                fdt_set_totalsize(buf, bufsize);
                return 0;
@@ -477,8 +477,8 @@ int fdt_open_into(const void *fdt, void *buf, int bufsize)
 
        fdt_set_magic(buf, FDT_MAGIC);
        fdt_set_totalsize(buf, bufsize);
-       fdt_set_version(buf, 17);
-       fdt_set_last_comp_version(buf, 16);
+       fdt_set_version(buf, FDT_LAST_SUPPORTED_VERSION);
+       fdt_set_last_comp_version(buf, FDT_LAST_COMPATIBLE_VERSION);
        fdt_set_boot_cpuid_phys(buf, fdt_boot_cpuid_phys(fdt));
 
        return 0;
-- 
2.43.0

 

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