linux-kernel - [PATCH v2] platform: cros_ec_debugfs: control uptime information request

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Date:   Tue, 26 May 2020 11:53:28 -0700
From:   Gwendal Grignou <gwendal@...omium.org>
To:     groeck@...omium.org, bleung@...omium.org,
        enric.balletbo@...labora.com, twawrzynczak@...omium.org
Cc:     linux-kernel@...r.kernel.org,
        Gwendal Grignou <gwendal@...omium.org>
Subject: [PATCH v2] platform: cros_ec_debugfs: control uptime information request

When EC does not support uptime command (EC_CMD_GET_UPTIME_INFO),
do not create the uptime sysfs entry point.
User space application will not probe the file needlessly.

The EC console log will not contain EC_CMD_GET_UPTIME_INFO anymore.

Signed-off-by: Gwendal Grignou <gwendal@...omium.org>
---
 drivers/platform/chrome/cros_ec_debugfs.c | 24 +++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
index 6ae484989d1f5..303a8c4686f89 100644
--- a/drivers/platform/chrome/cros_ec_debugfs.c
+++ b/drivers/platform/chrome/cros_ec_debugfs.c
@@ -243,6 +243,25 @@ static ssize_t cros_ec_pdinfo_read(struct file *file,
 				       read_buf, p - read_buf);
 }
 
+static bool cros_ec_uptime_is_supported(struct cros_ec_device *ec_dev)
+{
+	struct {
+		struct cros_ec_command cmd;
+		struct ec_response_uptime_info resp;
+	} __packed msg = {};
+	int ret;
+
+	msg.cmd.command = EC_CMD_GET_UPTIME_INFO;
+	msg.cmd.insize = sizeof(msg.resp);
+
+	ret = cros_ec_cmd_xfer_status(ec_dev, &msg.cmd);
+	if (ret == -EPROTO && msg.cmd.result == EC_RES_INVALID_COMMAND)
+		return false;
+
+	/* Other errors maybe a transient error, do not rule about support. */
+	return true;
+}
+
 static ssize_t cros_ec_uptime_read(struct file *file, char __user *user_buf,
 				   size_t count, loff_t *ppos)
 {
@@ -445,8 +464,9 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
 	debugfs_create_file("pdinfo", 0444, debug_info->dir, debug_info,
 			    &cros_ec_pdinfo_fops);
 
-	debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
-			    &cros_ec_uptime_fops);
+	if (cros_ec_uptime_is_supported(ec->ec_dev))
+		debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
+				    &cros_ec_uptime_fops);
 
 	debugfs_create_x32("last_resume_result", 0444, debug_info->dir,
 			   &ec->ec_dev->last_resume_result);
-- 
2.27.0.rc0.183.gde8f92d652-goog