eeprom: at24: support eeproms that do not auto-rollover reads

Some multi-address eeproms in the at24 family may not automatically
roll-over reads to the next slave address. On those eeproms, reads
that straddle slave boundaries will not work correctly.

Solution:
Mark such eeproms with a flag that prevents reads straddling
slave boundaries. Add the AT24_FLAG_NO_RDROL flag to the eeprom
entry in the device_id table, or add 'no-read-rollover' to the
eeprom devicetree entry.

Note that I have not personally enountered an at24 chip that
does not support read rollovers. They may or may not exist.
However, my hardware requires this functionality because of
a quirk.

Signed-off-by: Sven Van Asbroeck <svendev@arcx.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/platform_data/at24.h b/include/linux/platform_data/at24.h
index 271a4e25af67..841bb2815a41 100644
--- a/include/linux/platform_data/at24.h
+++ b/include/linux/platform_data/at24.h
@@ -50,6 +50,8 @@ struct at24_platform_data {
 #define AT24_FLAG_TAKE8ADDR	BIT(4)	/* take always 8 addresses (24c00) */
 #define AT24_FLAG_SERIAL	BIT(3)	/* factory-programmed serial number */
 #define AT24_FLAG_MAC		BIT(2)	/* factory-programmed mac address */
+#define AT24_FLAG_NO_RDROL  BIT(1)	/* does not auto-rollover reads to */
+					/* the next slave address */
 
 	void		(*setup)(struct nvmem_device *nvmem, void *context);
 	void		*context;