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From:   Eizan Miyamoto <eizan@chromium.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Eizan Miyamoto <eizan@chromium.org>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>
Subject: [PATCH v1] platform/chrome: cros_ec_debugfs: conditionally create uptime node
Date:   Wed,  8 Jul 2020 14:53:00 +1000
Message-Id: <20200708145215.v1.1.I9d49b374536424fcc98bc6bd935cdab8fac2ae71@changeid>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Before creating an 'uptime' node in debugfs, this change adds a check to
see if a EC_CMD_GET_UPTIME_INFO command can be successfully run.

If the uptime node is created, userspace programs may periodically poll
it (e.g., timberslide), causing commands to be sent to the EC each time.
If the EC doesn't support EC_CMD_GET_UPTIME_INFO, an error will be
emitted in the EC console, producing noise.

Signed-off-by: Eizan Miyamoto <eizan@chromium.org>
---

 drivers/platform/chrome/cros_ec_debugfs.c | 35 +++++++++++++++++------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
index ecfada00e6c51..8708fe12f8ca8 100644
--- a/drivers/platform/chrome/cros_ec_debugfs.c
+++ b/drivers/platform/chrome/cros_ec_debugfs.c
@@ -242,17 +242,14 @@ static ssize_t cros_ec_pdinfo_read(struct file *file,
 				       read_buf, p - read_buf);
 }
 
-static ssize_t cros_ec_uptime_read(struct file *file, char __user *user_buf,
-				   size_t count, loff_t *ppos)
+static int cros_ec_get_uptime(struct cros_ec_device *ec_dev,
+			      uint32_t *uptime)
 {
-	struct cros_ec_debugfs *debug_info = file->private_data;
-	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
 	struct {
 		struct cros_ec_command cmd;
 		struct ec_response_uptime_info resp;
 	} __packed msg = {};
 	struct ec_response_uptime_info *resp;
-	char read_buf[32];
 	int ret;
 
 	resp = (struct ec_response_uptime_info *)&msg.resp;
@@ -264,8 +261,24 @@ static ssize_t cros_ec_uptime_read(struct file *file, char __user *user_buf,
 	if (ret < 0)
 		return ret;
 
-	ret = scnprintf(read_buf, sizeof(read_buf), "%u\n",
-			resp->time_since_ec_boot_ms);
+	*uptime = resp->time_since_ec_boot_ms;
+	return 0;
+}
+
+static ssize_t cros_ec_uptime_read(struct file *file, char __user *user_buf,
+				   size_t count, loff_t *ppos)
+{
+	struct cros_ec_debugfs *debug_info = file->private_data;
+	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
+	char read_buf[32];
+	int ret;
+	uint32_t uptime;
+
+	ret = cros_ec_get_uptime(ec_dev, &uptime);
+	if (ret < 0)
+		return ret;
+
+	ret = scnprintf(read_buf, sizeof(read_buf), "%u\n", uptime);
 
 	return simple_read_from_buffer(user_buf, count, ppos, read_buf, ret);
 }
@@ -425,6 +438,7 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
 	const char *name = ec_platform->ec_name;
 	struct cros_ec_debugfs *debug_info;
 	int ret;
+	uint32_t uptime;
 
 	debug_info = devm_kzalloc(ec->dev, sizeof(*debug_info), GFP_KERNEL);
 	if (!debug_info)
@@ -444,8 +458,11 @@ 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_get_uptime(debug_info->ec->ec_dev, &uptime) >= 0)
+		debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
+				    &cros_ec_uptime_fops);
+	else
+		dev_dbg(ec->dev, "EC does not provide uptime");
 
 	debugfs_create_x32("last_resume_result", 0444, debug_info->dir,
 			   &ec->ec_dev->last_resume_result);
-- 
2.27.0.383.g050319c2ae-goog