linux-kernel - [RFC PATCH v3 12/18] ledtrig-blkdev: Add sysfs attributes to [dis]associate LEDs & devices

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Message-Id: <20210819025053.222710-13-arequipeno@gmail.com>
Date:   Wed, 18 Aug 2021 21:50:47 -0500
From:   Ian Pilcher <arequipeno@...il.com>
To:     linux-block@...r.kernel.org, linux-leds@...r.kernel.org
Cc:     axboe@...nel.dk, pavel@....cz, kabel@...nel.org,
        linux-kernel@...r.kernel.org, kernelnewbies@...nelnewbies.org
Subject: [RFC PATCH v3 12/18] ledtrig-blkdev: Add sysfs attributes to [dis]associate LEDs & devices

/sys/class/leds/<led>/add_blkdev - to create device/LED associations

/sys/class/leds/<led>/delete_blkdev to remove device/LED associations

For both attributes, accept multiple device names separated by whitespace

Signed-off-by: Ian Pilcher <arequipeno@...il.com>
---
 drivers/leds/trigger/ledtrig-blkdev.c | 48 +++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/drivers/leds/trigger/ledtrig-blkdev.c b/drivers/leds/trigger/ledtrig-blkdev.c
index a1646752b9a0..15b15aefdfd8 100644
--- a/drivers/leds/trigger/ledtrig-blkdev.c
+++ b/drivers/leds/trigger/ledtrig-blkdev.c
@@ -480,3 +480,51 @@ static int blkdev_disk_add(struct ledtrig_blkdev_led *const led,
 exit_return:
 	return ret;
 }
+
+
+/*
+ *
+ *	sysfs attributes to add & delete devices from LEDs
+ *
+ */
+
+static ssize_t blkdev_add_or_del(struct device *const dev,
+				 struct device_attribute *const attr,
+				 const char *const buf, const size_t count);
+
+static struct device_attribute ledtrig_blkdev_attr_add =
+	__ATTR(add_blkdev, 0200, NULL, blkdev_add_or_del);
+
+static struct device_attribute ledtrig_blkdev_attr_del =
+	__ATTR(delete_blkdev, 0200, NULL, blkdev_add_or_del);
+
+static ssize_t blkdev_add_or_del(struct device *const dev,
+				 struct device_attribute *const attr,
+				 const char *const buf, const size_t count)
+{
+	struct ledtrig_blkdev_led *const led = led_trigger_get_drvdata(dev);
+	const char *const disk_name = blkdev_skip_space(buf);
+	const char *const endp = blkdev_find_space(disk_name);
+	const ptrdiff_t name_len = endp - disk_name;	/* always >= 0 */
+	int ret;
+
+	if (name_len == 0) {
+		pr_info("blkdev LED: empty block device name\n");
+		return -EINVAL;
+	}
+
+	if (attr == &ledtrig_blkdev_attr_del) {
+		blkdev_disk_delete(led, disk_name, name_len);
+	} else {	/* attr == &ledtrig_blkdev_attr_add */
+		ret = blkdev_disk_add(led, disk_name, name_len);
+		if (ret != 0)
+			return ret;
+	}
+
+	/*
+	 * Consume everything up to the next non-whitespace token (or the end
+	 * of the input).  Avoids "empty block device name" error if there is
+	 * whitespace after the last token (e.g. a newline).
+	 */
+	return blkdev_skip_space(endp) - buf;
+}
-- 
2.31.1