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Date:   Sat, 29 Aug 2020 23:59:37 -0700
From:   Gwendal Grignou <>
        Gwendal Grignou <>
Subject: [PATCH v3] platform: cros_ec: Reduce ligthbar get version command

By default, the lightbar commands are set to the
biggest lightbar command and response. That length is greater than 128
bytes and may not work on all machines.
But all EC are probed for lightbar by sending a get version request.
Set that request size precisely.

Before the command would be:
cros_ec_cmd: version: 0, command: EC_CMD_LIGHTBAR_CMD, outsize: 194, insize: 128, result: 0
cros_ec_cmd: version: 0, command: EC_CMD_LIGHTBAR_CMD, outsize: 1, insize: 8, result: 0

Fixes: a841178445bb7 ("mfd: cros_ec: Use a zero-length array for command data")
Signed-off-by: Gwendal Grignou <>
Changes since v2:
- Add fix field where the inefficiency was present.

Changes since v1:
- Remove BUG and TEST fields.

 drivers/platform/chrome/cros_ec_lightbar.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c
index b59180bff5a3e..ef61298c30bdd 100644
--- a/drivers/platform/chrome/cros_ec_lightbar.c
+++ b/drivers/platform/chrome/cros_ec_lightbar.c
@@ -116,6 +116,8 @@ static int get_lightbar_version(struct cros_ec_dev *ec,
 	param = (struct ec_params_lightbar *)msg->data;
 	param->cmd = LIGHTBAR_CMD_VERSION;
+	msg->outsize = sizeof(param->cmd);
+	msg->result = sizeof(resp->version);
 	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
 	if (ret < 0) {
 		ret = 0;

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