On Wed, Dec 11, 2013 at 11:02:18AM +0100, Marek Vasut wrote:

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+
+	/* the two fundamental primitives */
+	int (*read_xfer)(struct spi_nor *nor, struct spi_nor_xfer_cfg *cfg,
+			 u8 *buf, size_t len);
+	int (*write_xfer)(struct spi_nor *nor, struct spi_nor_xfer_cfg *cfg,
+			  u8 *buf, size_t len);
+
+	int (*read_reg)(struct spi_nor *nor, u8 opcode, u8 *buf, int len);
+	int (*write_reg)(struct spi_nor *nor, u8 opcode, u8 *buf, int len,
+			int write_enable);

This stuff -- I mean 'read SPI NOR register' and 'write SPI NOR register'. I 
would love to see an API which grows as needed, not an API which is bloated by 
unused function right from the start.

I should send out my fsl-quadspi driver in the next version.

The read_reg/write_reg are implemented by the m25p80 and fsl-quadspi
now.

I think Lee's driver can implemente the read_xfer/write_xfer.

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+	const struct spi_device_id *(*read_id)(struct spi_nor *nor);
+	int (*wait_till_ready)(struct spi_nor *nor);
+
+	/* write */
+	void (*write)(struct spi_nor *nor, loff_t to,
+			size_t len, size_t *retlen, const u_char *buf);
+	/* read */
+	int (*read)(struct spi_nor *nor, loff_t from,
+			size_t len, size_t *retlen, u_char *buf);
+	/* erase */
+	int (*erase)(struct spi_nor *nor, loff_t offs);

How do you specify what to erase (sub-sector, sector, whole chip) here ?

I use a write_reg(OPCODE_ERASE_CHIP) to erase the whole chip.
Please read the patch 3.

This hook is used to erase a sector.

I suspect we might need a much better documentation for this structure, it is 
hardly clear which function does what ;-)

sorry, i will add more comment in the next version.

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Btw, what is the sub-sector mean? which opcodes for the sub-sector?

On large chips with for example 64K big sectors, you can erase a sub-sector 
area, usually a 4K one. This reduces the wear of the chip. See these defines in 
m25p80.c :

  46 #define OPCODE_BE_4K            0x20    /* Erase 4KiB block */
  48 #define OPCODE_BE_32K           0x52    /* Erase 32KiB block */
  49 #define OPCODE_CHIP_ERASE       0xc7    /* Erase whole flash chip */

ok.

the @erase hook can be used for sub-sector too.

thanks
Huang Shijie