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Subject[PATCH v4 4/7] i2c: bcm2835: Can't support I2C_M_IGNORE_NAK
The controller can't support this flag, so remove it.

Documentation/i2c/i2c-protocol states that all of the message is sent:

Normally message is interrupted immediately if there is [NA] from the
client. Setting this flag treats any [NA] as [A], and all of
message is sent.

From the BCM2835 ARM Peripherals datasheet:

The ERR field is set when the slave fails to acknowledge either
its address or a data byte written to it.

So when the controller doesn't receive an ack, it sets ERR and raises
an interrupt. In other words, the whole message is not sent.

Signed-off-by: Noralf Trønnes <>
Reviewed-by: Eric Anholt <>
drivers/i2c/busses/i2c-bcm2835.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index 54d510a..565ef69 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -212,10 +212,6 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
if (likely(!i2c_dev->msg_err))
return 0;

- if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
- (msg->flags & I2C_M_IGNORE_NAK))
- return 0;
dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);

if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
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