linux-kernel - [PATCH v2 1/5] mfd: cros-ec: Fix host command buffer size

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Date:   Mon,  3 Apr 2017 18:35:32 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Jonathan Cameron <jic23@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Olof Johansson <olof@...om.net>, bleung@...omium.org
Cc:     martinez.javier@...il.com, Guenter Roeck <groeck@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        rtc-linux@...glegroups.com, Vic Yang <victoryang@...gle.com>
Subject: [PATCH v2 1/5] mfd: cros-ec: Fix host command buffer size

From: Vic Yang <victoryang@...gle.com>

For SPI, we can get up to 32 additional bytes for response preamble.
The current overhead (2 bytes) may cause problems when we try to receive
a big response. Update it to 32 bytes.

Without this fix we could see a kernel BUG when we receive a big response
from the Chrome EC when is connected via SPI.

Signed-off-by: Vic Yang <victoryang@...gle.com>
Tested-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
---

  This patch is a FIX, and I think that would be interesting see it merged
in this release cycle. This should go through the MFD tree and can be picked
independently of the other patches. Lee Jones I think this is for you.

Changes since v1:
 - None

 include/linux/mfd/cros_ec.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index b3e812f..3b16c90 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -35,10 +35,11 @@
  * Max bus-specific overhead incurred by request/responses.
  * I2C requires 1 additional byte for requests.
  * I2C requires 2 additional bytes for responses.
+ * SPI requires up to 32 additional bytes for responses.
  * */
 #define EC_PROTO_VERSION_UNKNOWN	0
 #define EC_MAX_REQUEST_OVERHEAD		1
-#define EC_MAX_RESPONSE_OVERHEAD	2
+#define EC_MAX_RESPONSE_OVERHEAD	32
 
 /*
  * Command interface between EC and AP, for LPC, I2C and SPI interfaces.
-- 
2.9.3