docs: mtd: move it to the driver-api book

[linux-2.6-block.git] / Documentation / mtd / spi-nor.rst

diff --git a/Documentation/mtd/spi-nor.rst b/Documentation/mtd/spi-nor.rst
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-=================
-SPI NOR framework
-=================
-
-Part I - Why do we need this framework?
----------------------------------------
-
-SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus
-controller operates agnostic of the specific device attached. However, some
-controllers (such as Freescale's QuadSPI controller) cannot easily handle
-arbitrary streams of bytes, but rather are designed specifically for SPI NOR.
-
-In particular, Freescale's QuadSPI controller must know the NOR commands to
-find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of
-opcodes, addresses, or data payloads; a SPI controller simply knows to send or
-receive bytes (Tx and Rx). Therefore, we must define a new layering scheme under
-which the controller driver is aware of the opcodes, addressing, and other
-details of the SPI NOR protocol.
-
-Part II - How does the framework work?
---------------------------------------
-
-This framework just adds a new layer between the MTD and the SPI bus driver.
-With this new layer, the SPI NOR controller driver does not depend on the
-m25p80 code anymore.
-
-Before this framework, the layer is like::
-
-                   MTD
-         ------------------------
-                  m25p80
-         ------------------------
-              SPI bus driver
-         ------------------------
-               SPI NOR chip
-
-   After this framework, the layer is like:
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                  m25p80
-         ------------------------
-              SPI bus driver
-         ------------------------
-              SPI NOR chip
-
-  With the SPI NOR controller driver (Freescale QuadSPI), it looks like:
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                fsl-quadSPI
-         ------------------------
-              SPI NOR chip
-
-Part III - How can drivers use the framework?
----------------------------------------------
-
-The main API is spi_nor_scan(). Before you call the hook, a driver should
-initialize the necessary fields for spi_nor{}. Please see
-drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to fsl-quadspi.c
-when you want to write a new driver for a SPI NOR controller.
-Another API is spi_nor_restore(), this is used to restore the status of SPI
-flash chip such as addressing mode. Call it whenever detach the driver from
-device or reboot the system.