driver-api/mtd/spi-nor.rst

2 SPI NOR framework
5 Part I - Why do we need this framework?
6 ---------------------------------------
8 SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus
11 arbitrary streams of bytes, but rather are designed specifically for SPI NOR.
13 In particular, Freescale's QuadSPI controller must know the NOR commands to
14 find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of
15 opcodes, addresses, or data payloads; a SPI controller simply knows to send or
18 details of the SPI NOR protocol.
20 Part II - How does the framework work?
21 --------------------------------------
23 This framework just adds a new layer between the MTD and the SPI bus driver.
24 With this new layer, the SPI NOR controller driver does not depend on the
30          ------------------------
32          ------------------------
33 	       SPI bus driver
34          ------------------------
35 	        SPI NOR chip
39          ------------------------
40               SPI NOR framework
41          ------------------------
43          ------------------------
44 	       SPI bus driver
45          ------------------------
46 	       SPI NOR chip
48   With the SPI NOR controller driver (Freescale QuadSPI), it looks like:
50          ------------------------
51               SPI NOR framework
52          ------------------------
53                 fsl-quadSPI
54          ------------------------
55 	       SPI NOR chip
57 Part III - How can drivers use the framework?
58 ---------------------------------------------
62 drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c
63 when you want to write a new driver for a SPI NOR controller.
64 Another API is spi_nor_restore(), this is used to restore the status of SPI