[PATCH] of/fdt: remove redundant memset in __unflatten_device_tree()

[PATCH] of/fdt: remove redundant memset in __unflatten_device_tree()

[Sang-Heon Jeon]

All dt_alloc callbacks passed to __unflatten_device_tree() already
return zero-initialized memory.

- kernel_tree_alloc uses kzalloc()
- early_init_dt_alloc_memory_arch() and dt_alloc_memory() both use
  memblock_alloc()

So remove redundant memset after the allocation. No funtional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
dt-test result

[    0.529540] ### dt-test ### start of unittest - you will see error messages
[    0.532758] ### dt-test ### EXPECT \ : Duplicate name in testcase-data, renamed to "duplicate-name#1"
[    0.537608] ### dt-test ### EXPECT / : Duplicate name in testcase-data, renamed to "duplicate-name#1"

...

[    0.781700] ### dt-test ### EXPECT / : OF: resolver: overlay phandle fixup failed: -22
[    0.781718] ### dt-test ### EXPECT / : OF: resolver: node label 'this_label_does_not_exist' not found in live devicetree symbols table
[    0.781945] ### dt-test ### end of unittest - 423 passed, 0 failed

---
Hello, 

While looking into boot information, I found a minor enhancement point.
If I misunderstood anything, please feel free to let me know.

Thank you for taking valuable time to review this work.

Best Regards,
Sang-Heon Jeon
---
 drivers/of/fdt.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index becc855ff8b5..647bff2c4521 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -391,8 +391,6 @@ void *__unflatten_device_tree(const void *blob,
 	if (!mem)
 		return NULL;
 
-	memset(mem, 0, size);
-
 	*(__be32 *)(mem + size) = cpu_to_be32(0xdeadbeef);
 
 	pr_debug("  unflattening %p...\n", mem);
-- 
2.43.0

Re: [PATCH] of/fdt: remove redundant memset in __unflatten_device_tree()

[Rob Herring (Arm)]

On Sat, 18 Apr 2026 23:04:20 +0900, Sang-Heon Jeon wrote:
> All dt_alloc callbacks passed to __unflatten_device_tree() already
> return zero-initialized memory.
> 
> - kernel_tree_alloc uses kzalloc()
> - early_init_dt_alloc_memory_arch() and dt_alloc_memory() both use
>   memblock_alloc()
> 
> So remove redundant memset after the allocation. No funtional change.

That is true now, but it wasn't the case before memblock became used on 
all arches.

I've updated the commit message with this info and applied.

Rob

Re: [PATCH] of/fdt: remove redundant memset in __unflatten_device_tree()

[Sang-Heon Jeon]

Hi,

On Wed, Apr 22, 2026 at 4:34 AM Rob Herring (Arm) <robh@kernel.org> wrote:
>
>
> On Sat, 18 Apr 2026 23:04:20 +0900, Sang-Heon Jeon wrote:
> > All dt_alloc callbacks passed to __unflatten_device_tree() already
> > return zero-initialized memory.
> >
> > - kernel_tree_alloc uses kzalloc()
> > - early_init_dt_alloc_memory_arch() and dt_alloc_memory() both use
> >   memblock_alloc()
> >
> > So remove redundant memset after the allocation. No funtional change.
>
> That is true now, but it wasn't the case before memblock became used on
> all arches.
>
> I've updated the commit message with this info and applied.

Thanks for spotting that and for your review :)

> Rob

Best Regards,
Sang-Heon Jeon