i2c: xiic: Add max_read_len quirk
authorRobert Hancock <hancock@sedsystems.ca>
Tue, 4 Jun 2019 21:55:51 +0000 (15:55 -0600)
committerWolfram Sang <wsa@the-dreams.de>
Fri, 7 Jun 2019 22:24:07 +0000 (00:24 +0200)
commit49b809586730a77b57ce620b2f9689de765d790b
treebc698583e76b10d7b3907caa426e4b2d2a8b50dd
parentf2c7c76c5d0a443053e94adb9f0918fa2fb85c3a
i2c: xiic: Add max_read_len quirk

This driver does not support reading more than 255 bytes at once because
the register for storing the number of bytes to read is only 8 bits. Add
a max_read_len quirk to enforce this.

This was found when using this driver with the SFP driver, which was
previously reading all 256 bytes in the SFP EEPROM in one transaction.
This caused a bunch of hard-to-debug errors in the xiic driver since the
driver/logic was treating the number of bytes to read as zero.
Rejecting transactions that aren't supported at least allows the problem
to be diagnosed more easily.

Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
drivers/i2c/busses/i2c-xiic.c