[PATCH v15 09/13] counter: Implement signalZ_action_component_id sysfs attribute

[William Breathitt Gray]

The Generic Counter chrdev interface expects users to supply component
IDs in order to select Synapses for requests. In order for users to know
what component ID belongs to which Synapse this information must be
exposed. The signalZ_action_component_id attribute provides a way for
users to discover what component ID belongs to the respective Synapse.

Cc: Gwendal Grignou <gwendal at chromium.org>
Cc: Dan Carpenter <dan.carpenter at oracle.com>
Reviewed-by: David Lechner <david at lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray at gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-counter |  7 ++++
 drivers/counter/counter-sysfs.c             | 46 ++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index dee79b606847..9809d8a47431 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -203,6 +203,13 @@ Description:
 		both edges:
 			Any state transition.
 
+What:		/sys/bus/counter/devices/counterX/countY/signalZ_action_component_id
+KernelVersion:	5.15
+Contact:	linux-iio at vger.kernel.org
+Description:
+		Read-only attribute that indicates the component ID of the
+		respective Synapse of Count Y for Signal Z.
+
 What:		/sys/bus/counter/devices/counterX/countY/spike_filter_ns
 KernelVersion:	5.14
 Contact:	linux-iio at vger.kernel.org
diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
index dbb507c9da11..11bef9f8190f 100644
--- a/drivers/counter/counter-sysfs.c
+++ b/drivers/counter/counter-sysfs.c
@@ -393,7 +393,6 @@ static int counter_avail_attr_create(struct device *const dev,
 	struct counter_attribute *counter_attr;
 	struct device_attribute *dev_attr;
 
-	/* Allocate Counter attribute */
 	counter_attr = devm_kzalloc(dev, sizeof(*counter_attr), GFP_KERNEL);
 	if (!counter_attr)
 		return -ENOMEM;
@@ -535,6 +534,46 @@ static int counter_name_attr_create(struct device *const dev,
 	return 0;
 }
 
+static ssize_t counter_comp_id_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	const size_t id = (size_t)to_counter_attribute(attr)->comp.priv;
+
+	return sprintf(buf, "%zu\n", id);
+}
+
+static int counter_comp_id_attr_create(struct device *const dev,
+				       struct counter_attribute_group *const group,
+				       const char *name, const size_t id)
+{
+	struct counter_attribute *counter_attr;
+
+	/* Allocate Counter attribute */
+	counter_attr = devm_kzalloc(dev, sizeof(*counter_attr), GFP_KERNEL);
+	if (!counter_attr)
+		return -ENOMEM;
+
+	/* Generate component ID name */
+	name = devm_kasprintf(dev, GFP_KERNEL, "%s_component_id", name);
+	if (!name)
+		return -ENOMEM;
+
+	/* Configure Counter attribute */
+	counter_attr->comp.priv = (void *)id;
+
+	/* Configure device attribute */
+	sysfs_attr_init(&counter_attr->dev_attr.attr);
+	counter_attr->dev_attr.attr.name = name;
+	counter_attr->dev_attr.attr.mode = 0444;
+	counter_attr->dev_attr.show = counter_comp_id_show;
+
+	/* Store list node */
+	list_add(&counter_attr->l, &group->attr_list);
+	group->num_attr++;
+
+	return 0;
+}
+
 static struct counter_comp counter_signal_comp = {
 	.type = COUNTER_COMP_SIGNAL_LEVEL,
 	.name = "signal",
@@ -629,6 +668,11 @@ static int counter_sysfs_synapses_add(struct counter_device *const counter,
 					  COUNTER_SCOPE_COUNT, count);
 		if (err < 0)
 			return err;
+
+		/* Create Synapse component ID attribute */
+		err = counter_comp_id_attr_create(dev, group, comp.name, i);
+		if (err < 0)
+			return err;
 	}
 
 	return 0;
-- 
2.32.0