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portal_mtd: set writebufsize so UBI can attach to hyperfile MTD #90

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Merged
lacraig2 merged 1 commit into from
Jul 15, 2026
Merged

portal_mtd: set writebufsize so UBI can attach to hyperfile MTD #90

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11 changes: 11 additions & 0 deletions src/portal/portal_mtd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,17 @@ void handle_op_mtd_create(portal_region *mem_region)
mtd->size = req_total_size;
mtd->erasesize = req_erasesize;
mtd->writesize = req_writesize;
/*
* UBI validates the write-buffer size (max_write_size): it must be
* >= min_io_size (writesize), a multiple of it, and a power of 2
* (see ubi_attach_mtd_dev() in drivers/mtd/ubi/build.c). We previously
* left writebufsize at 0, so attaching UBI to one of these devices failed
* with "ubi_attach_mtd_dev: bad write buffer size 0 for N min. I/O unit".
* Setting it to the write (page) size lets UBI/UBIFS attach to
* hyperfile-backed MTD partitions, which vendor firmware relies on for
* UBI-mounted nvram/config partitions.
*/
mtd->writebufsize = req_writesize;
mtd->oobsize = req->is_nand ? req->oob_size : 0;
mtd->owner = THIS_MODULE;
mtd->priv = entry;
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