Many NOR flash chips comes with One-Time-Programmable area a.k.a security registers. This RFC patchset aims at adding generic OTP support in SPI-NOR to read/write user OTP area.
In SPI-NOR framework, OTP specific read/write methods will use read_xfer/write_xfer hooks. So PATCH 1, reverts "unused read_xfer/ write_xfer hooks." PATCH 2 changes return value of read_xfer/write_xfer to allow returning amount of data transferred and errors as read(2)/write(2). This makes them inline with current read/write hooks. PATCH 3 modified helpers in m25p80.c so that those can be used from read_xfer/write_xfer methods. PATCH 4 implements read_xfer/write_xfer in m25p80.c PATCH 5 implements generic support to read/write user OTP. And finally in PATCH 6 user OTP support for s25fl016k is enabled. Overall changes are as follows: New flag SPI_NOR_HAS_OTP is added to specify chip has OTP area. Using OTP_INFO macro, details of OTP area can be specified. It includes size of area, number of OTP areas/banks, starting address and difference between consecutive OTP banks. OTP framework will give user linear address view from 0 to size of OTP area. User don't need to specify actual physical address of OTP area for reading/writing. Details which could be specific to manufacturer like opcodes for read/write/erase can be specified based on manufacturer. Generic OTP read/write methods are added so as it can be used for OTP support from other manufacturer. This complete patchset is tested with Winbond NOR flash W25Q16DV which is detected as "s25fl016k" by SPI-NOR. I've plans to add support for locking these OTP areas and reading factory OTP area as well. But before that I would to get comments on this initial part to understand if I'm going in right direction. Cc: David Woodhouse <dw...@infradead.org> Cc: Brian Norris <computersforpe...@gmail.com> Cc: Boris Brezillon <boris.brezil...@free-electrons.com> Cc: Marek Vasut <marek.va...@gmail.com> Cc: Richard Weinberger <rich...@nod.at> Cc: Cyrille Pitchen <cyrille.pitc...@atmel.com> Rahul Bedarkar (6): Revert "mtd: spi-nor: remove unused read_xfer/write_xfer hooks" mtd: spi-nor: change return value of read_xfer and write_xfer mtd: m25p80: don't pass spi_nor to helper methods mtd: m25p80: implement read_xfer and write_xfer mtd: spi-nor: add support to read/write user OTP mtd: spi-nor: enable OTP support for s25fl016k drivers/mtd/devices/m25p80.c | 111 ++++++++++++--- drivers/mtd/spi-nor/spi-nor.c | 314 +++++++++++++++++++++++++++++++++++++++++- include/linux/mtd/spi-nor.h | 52 +++++++ 3 files changed, 460 insertions(+), 17 deletions(-) -- 2.6.2
