linux-kernel - [PATCH v2 4/8] i2c: bcm2835: Can't support I2C_M_IGNORE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1474977426-3272-5-git-send-email-noralf@tronnes.org>
Date:   Tue, 27 Sep 2016 13:57:02 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     wsa@...-dreams.de, swarren@...dotorg.org, eric@...olt.net
Cc:     linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org,
        Noralf Trønnes <noralf@...nnes.org>
Subject: [PATCH v2 4/8] 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:

I2C_M_IGNORE_NAK:
    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 <noralf@...nnes.org>
---
 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 370a322..4e08add 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -203,10 +203,6 @@ 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_err_ratelimited(i2c_dev->dev, "i2c transfer failed: %x\n",
 			    i2c_dev->msg_err);
 
-- 
2.8.2