drivers/eeprom: Set the bus frequency

[ajuckler]

Summary

Add EEPIOC_SETSPEED ioctl acting like the MTDIOC_SETSPEED ioctl.
The default frequency is taken from the Kconfig and can be adjusted at runtime using this ioctl.

The SPI timing configuration parameters from mtd/at25ee have also been copied so that they can be applied to eeprom/spi_xx25xx.

Impact

If CONFIG_SPI_DELAY_CONTROL is set, SPI timing parameters will be explicitly set when communicating with the eeprom/spi_xx25xx device.

As long as the new ioctl command is not used, the EEPROM drivers behaviour is unchanged.

Testing

Tested on a custom target (STM32F7-based) with a Rhom BR25G256FVT EEPROM (equivalent to a Microchip 25xx256).

Changes to the i2c_xx24xx driver have been compiled only.

[linguini1]

Please update the impact section, it isn't none if you've changed the driver.

Also, I don't think these changes should be merged until they are tested with an I2C based EEPROM (since you mentioned you only compile tested that). I have a board with one, I can try to test this patch against it in the next few days (unless someone else beats me to it).

[ajuckler]

Please update the impact section, it isn't none if you've changed the driver.

Also, I don't think these changes should be merged until they are tested with an I2C based EEPROM (since you mentioned you only compile tested that). I have a board with one, I can try to test this patch against it in the next few days (unless someone else beats me to it).

Updated, I meant "none" in the sense that as long as the ioctl isn't called the behaviour doesn't differ from the current one.

I don't have a I2C EEPROM at hand so any help in testing this bit is definitely welcome.

[linguini1]

Had a chance to test with my I2C-based EEPROM today (24C32FP by ST). Functional to read from as a character device still.

[ajuckler]

Had a chance to test with my I2C-based EEPROM today (24C32FP by ST). Functional to read from as a character device still.

Great, thank you very much for testing