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.

---
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.

Signed-off-by: Christian Thießen <[email protected]>
---
 drivers/mtd/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mtd/core.c b/drivers/mtd/core.c
index 
6162ec450fc1c3a0fa6339042c4d627e0f9567d0..7ca8fc900af4666070b03ef5f945748d60e6a6e7
 100644
--- a/drivers/mtd/core.c
+++ b/drivers/mtd/core.c
@@ -436,6 +436,7 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info 
*instr)
 {
        if (instr->addr >= mtd->size || instr->len > mtd->size - instr->addr)
                return -EINVAL;
+#ifdef CONFIG_MTD_WRITE
        if (!(mtd->flags & MTD_WRITEABLE))
                return -EROFS;
        instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
@@ -443,6 +444,9 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info 
*instr)
                return 0;
 
        return mtd->_erase(mtd, instr);
+#else
+       return -ENOSYS;
+#endif
 }
 
 int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)

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

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



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