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Date:   Thu,  7 Jul 2022 15:15:15 -0700
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Subject: [PATCH v3 2/3] Bluetooth: Add sysfs entry to enable/disable devcoredump
From:   Manish Mandlik <mmandlik@google.com>
To:     marcel@holtmann.org, luiz.dentz@gmail.com
Cc:     linux-bluetooth@vger.kernel.org,
        chromeos-bluetooth-upstreaming@chromium.org,
        Manish Mandlik <mmandlik@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Since device/firmware dump is a debugging feature, we may not need it
all the time. Add a sysfs attribute to enable/disable bluetooth
devcoredump capturing. The default state of this feature would be
disabled and it can be enabled by echoing 1 to enable_coredump sysfs
entry as follow:

$ echo 1 > /sys/class/bluetooth/<device>/enable_coredump

Signed-off-by: Manish Mandlik <mmandlik@google.com>
---

Changes in v3:
- New patch in the series to enable/disable feature via sysfs entry

 net/bluetooth/hci_sysfs.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c
index 4e3e0451b08c..df0d54a5ae3f 100644
--- a/net/bluetooth/hci_sysfs.c
+++ b/net/bluetooth/hci_sysfs.c
@@ -91,9 +91,45 @@ static void bt_host_release(struct device *dev)
 	module_put(THIS_MODULE);
 }
 
+#ifdef CONFIG_DEV_COREDUMP
+static ssize_t enable_coredump_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct hci_dev *hdev = to_hci_dev(dev);
+
+	return scnprintf(buf, 3, "%d\n", hdev->dump.enabled);
+}
+
+static ssize_t enable_coredump_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct hci_dev *hdev = to_hci_dev(dev);
+
+	/* Consider any non-zero value as true */
+	if (simple_strtol(buf, NULL, 10))
+		hdev->dump.enabled = true;
+	else
+		hdev->dump.enabled = false;
+
+	return count;
+}
+DEVICE_ATTR_RW(enable_coredump);
+#endif
+
+static struct attribute *bt_host_attrs[] = {
+#ifdef CONFIG_DEV_COREDUMP
+	&dev_attr_enable_coredump.attr,
+#endif
+	NULL,
+};
+ATTRIBUTE_GROUPS(bt_host);
+
 static const struct device_type bt_host = {
 	.name    = "host",
 	.release = bt_host_release,
+	.groups = bt_host_groups,
 };
 
 void hci_init_sysfs(struct hci_dev *hdev)
-- 
2.37.0.rc0.161.g10f37bed90-goog