Re: [PATCH v2] HID: cp2112: support i2c write-read transfers in hid-cp2112

On Fri, Jul 10, 2015 at 5:21 PM, Jiri Kosina [off-list ref] wrote:

On Thu, 9 Jul 2015, Ellen Wang wrote:

quoted

cp2112_i2c_xfer() only supports a single i2c_msg.  More than
one message at a time just returns EIO.  This breaks certain
important cases.  For example, the at24 eeprom driver generates
paired write and read messages (for eeprom address and data).

Since the device doesn't support i2c repeated starts in general,
but does support a single write-repeated-start-read pair
(since hardware rev 1), we recognize the latter case and
implement only that.

Signed-off-by: Ellen Wang <redacted>

Applied to for-4.3/cp2112.

Good!

Either
Tested-by: Antonio Borneo <redacted>
and/or
Reviewed-by: Antonio Borneo <redacted>

By the way, while this patch extends the i2c functionality, it makes
clear that repeated start is always broken on HW rev 1, also for
SMBUS!
I'm testing a patch to restrict SMBUS on rev 1 to only those
transactions that don't require repeated start.
Will post it shortly.

Regards,
Antonio