From: Christian Thießen <[email protected]>

When CONFIG_MTD_WRITE is unset, the mtd->_erase member of partition
devices does not get initialized, so it remains NULL.
However when running ubiattach on an UBI partition, mtd_erase() still
gets called, tries to call mtd->_erase and crashes. Make it fail
gracefully by returning ENOSYS ("Function not implemented") instead.

Reviewed-by: Ahmad Fatoum <[email protected]>
Signed-off-by: Christian Thießen <[email protected]>
---
As discussed in https://github.com/barebox/barebox/issues/39 this patch
enables ubiattach-ing a NAND partition even if CONFIG_MTD_WRITE is
turned off, by making mtd_erase fail gracefully.
---
Hi,
thank you for the warm welcome and the constructive feedback!
Changes in v2: Addressed review comments.
- Changed from ifdef to IS_ENABLED
- Moved the sign-off tag to the commit message (why does b4 add it to
  the cover letter?)
- Link to v1: 
https://lore.kernel.org/r/[email protected]
---
 drivers/mtd/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/mtd/core.c b/drivers/mtd/core.c
index 
6162ec450fc1c3a0fa6339042c4d627e0f9567d0..bb579a8f5249981ec1623060ddb1b7056a06c1a0
 100644
--- a/drivers/mtd/core.c
+++ b/drivers/mtd/core.c
@@ -436,6 +436,8 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info 
*instr)
 {
        if (instr->addr >= mtd->size || instr->len > mtd->size - instr->addr)
                return -EINVAL;
+       if (!IS_ENABLED(CONFIG_MTD_WRITE))
+               return -ENOSYS;
        if (!(mtd->flags & MTD_WRITEABLE))
                return -EROFS;
        instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;

---
base-commit: b5561f3bdd4845b478e5b35aab04f1d8e71ea93b
change-id: 20250902-mtd-erase-enosys-2d80e4bc77c8

Best regards,
-- 
Christian Thießen <[email protected]>



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