[PATCH v2 0/3] mtd: maps: vmu-flash: Fix build and runtime errors

[PATCH v2 0/3] mtd: maps: vmu-flash: Fix build and runtime errors

[Florian Fuchs]

Hi all,

This small series fixes build and runtime errors in the vmu-flash driver
(enabled by CONFIG_MTD_VMU) and the included maple.h. These changes were
verified on real Dreamcast hardware with a physical VMU. The VMU can now
be successfully probed, read and written with MTD tools like mtdinfo and
mtd_debug. Previously, the driver failed to build or crashed during
probing.

        bash-5.3# mtdinfo /dev/mtd0
        mtd0
        Name:                           vmu2.1.0
        Type:                           mlc-nand
        Eraseblock size:                512 bytes
        Amount of eraseblocks:          256 (131072 bytes, 128.0 KiB)
        Minimum input/output unit size: 512 bytes
        Sub-page size:                  512 bytes                 
        Character device major/minor:   90:0
        Bad blocks are allowed:         true
        Device is writable:             true
                       
Thanks,
Florian
---
v1->v2: Rebased patches and fixed the hotplug issues in other sh
        patches.

v1: https://lore.kernel.org/linux-mtd/20251117224408.498449-1-fuchsfl@gmail.com/
   
The original v1 was postponed to fix the hotplug issue and other runtime
panics, that are fixed in the following patch:
"[PATCH v2] sh: maple: fix empty port handling":
https://lore.kernel.org/linux-sh/20260426212714.2286437-1-fuchsfl@gmail.com/
 
Note that in order to use the VMUs while there are empty ports, it
requires the above patch.

Florian Fuchs (3):
  mtd: maps: vmu-flash: fix build error due to missing include of
    linux/device.h
  mtd: maps: vmu-flash: fix fault in unaligned fixup
  mtd: maps: vmu-flash: Fix NULL pointer dereference in initialization

 drivers/mtd/maps/vmu-flash.c | 7 ++++---
 include/linux/maple.h        | 3 +--
 2 files changed, 5 insertions(+), 5 deletions(-)


base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
-- 
2.43.0

[PATCH v2 1/3] mtd: maps: vmu-flash: fix build error due to missing include of linux/device.h

[Florian Fuchs]

Fix build error by adding the missing include of linux/device.h
linux/maple.h embeds struct device via struct maple_device, which
requires the definition. Otherwise results in build error:

./include/linux/maple.h:81:16: error: field 'dev' has incomplete type
  struct device dev;
                ^~~
./include/linux/maple.h:86:23: error: field 'drv' has incomplete type
  struct device_driver drv;
                       ^~~

Fixes: 313162d0b838 ("device.h: audit and cleanup users in main include dir")
Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v1->v2: no functional change, just rebase patch

v1: https://lore.kernel.org/lkml/20251117224408.498449-2-fuchsfl@gmail.com/

 include/linux/maple.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/maple.h b/include/linux/maple.h
index 3be4e567473c..22f2930251ed 100644
--- a/include/linux/maple.h
+++ b/include/linux/maple.h
@@ -2,10 +2,9 @@
 #ifndef __LINUX_MAPLE_H
 #define __LINUX_MAPLE_H
 
+#include <linux/device.h>
 #include <mach/maple.h>
 
-struct device;
-
 /* Maple Bus command and response codes */
 enum maple_code {
 	MAPLE_RESPONSE_FILEERR =	-5,
-- 
2.43.0

[PATCH v2 2/3] mtd: maps: vmu-flash: fix fault in unaligned fixup

[Florian Fuchs]

Use kzalloc_obj() / kzalloc_objs() to allocate the memcard structs,
instead of kmalloc_obj() / kmalloc_objs() to prevent access to
uninitialized data.

Fixes runtime error: Fault in unaligned fixup: 0000 [#1] at
mtd_get_fact_prot_info.

Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v1->v2: no functional change, just rebased.

v1: https://lore.kernel.org/lkml/20251117224408.498449-3-fuchsfl@gmail.com/

 drivers/mtd/maps/vmu-flash.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/maps/vmu-flash.c b/drivers/mtd/maps/vmu-flash.c
index 75e06d249ce9..b76d0609d1b7 100644
--- a/drivers/mtd/maps/vmu-flash.c
+++ b/drivers/mtd/maps/vmu-flash.c
@@ -609,7 +609,7 @@ static int vmu_connect(struct maple_device *mdev)
 
 	basic_flash_data = be32_to_cpu(mdev->devinfo.function_data[c - 1]);
 
-	card = kmalloc_obj(struct memcard);
+	card = kzalloc_obj(struct memcard);
 	if (!card) {
 		error = -ENOMEM;
 		goto fail_nomem;
@@ -627,13 +627,13 @@ static int vmu_connect(struct maple_device *mdev)
 	* Not sure there are actually any multi-partition devices in the
 	* real world, but the hardware supports them, so, so will we
 	*/
-	card->parts = kmalloc_objs(struct vmupart, card->partitions);
+	card->parts = kzalloc_objs(struct vmupart, card->partitions);
 	if (!card->parts) {
 		error = -ENOMEM;
 		goto fail_partitions;
 	}
 
-	card->mtd = kmalloc_objs(struct mtd_info, card->partitions);
+	card->mtd = kzalloc_objs(struct mtd_info, card->partitions);
 	if (!card->mtd) {
 		error = -ENOMEM;
 		goto fail_mtd_info;
-- 
2.43.0

Re: [PATCH v2 2/3] mtd: maps: vmu-flash: fix fault in unaligned fixup

[Miquel Raynal]

On 27/04/2026 at 13:47:49 +02, Florian Fuchs <fuchsfl@gmail.com> wrote:

> Use kzalloc_obj() / kzalloc_objs() to allocate the memcard structs,
> instead of kmalloc_obj() / kmalloc_objs() to prevent access to
> uninitialized data.
>
> Fixes runtime error: Fault in unaligned fixup: 0000 [#1] at
> mtd_get_fact_prot_info.

Shall this patch receive a Fixes tag if it actually fixes runtime
behaviour?

Also, please add the 'Cc: stable' line in your fixes.

Thanks,
Miquèl

[PATCH v2 3/3] mtd: maps: vmu-flash: Fix NULL pointer dereference in initialization

[Florian Fuchs]

The mtd_info contains a struct device, which must be linked to its
parent. Without this, the initialization of the MTD fails with a NULL
pointer dereference.

Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v1->v2: no functional change

v1: https://lore.kernel.org/lkml/20251117224408.498449-4-fuchsfl@gmail.com/

 drivers/mtd/maps/vmu-flash.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mtd/maps/vmu-flash.c b/drivers/mtd/maps/vmu-flash.c
index b76d0609d1b7..10244e6731d0 100644
--- a/drivers/mtd/maps/vmu-flash.c
+++ b/drivers/mtd/maps/vmu-flash.c
@@ -547,6 +547,7 @@ static void vmu_queryblocks(struct mapleq *mq)
 	mpart->partition = card->partition;
 	mtd_cur->priv = mpart;
 	mtd_cur->owner = THIS_MODULE;
+	mtd_cur->dev.parent = &mdev->dev;
 
 	pcache = kzalloc_obj(struct vmu_cache);
 	if (!pcache)
-- 
2.43.0

Re: [PATCH v2 3/3] mtd: maps: vmu-flash: Fix NULL pointer dereference in initialization

[Miquel Raynal]

On 27/04/2026 at 13:47:50 +02, Florian Fuchs <fuchsfl@gmail.com> wrote:

> The mtd_info contains a struct device, which must be linked to its
> parent. Without this, the initialization of the MTD fails with a NULL
> pointer dereference.
>
> Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
> ---

For how long as this been broken? Is it really used?

Anyway, also here you will need to Cc stable and add a fixes tag.

Thanks,
Miquèl