linux-kernel - [PATCH 3/3] Input: cros-ec-keyb - Expose function row physical map to userspace

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Date:   Mon, 21 Dec 2020 17:47:59 -0800
From:   Philip Chen <philipchen@...omium.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     dtor@...omium.org, swboyd@...omium.org, dianders@...omium.org,
        rajatja@...omium.org, Philip Chen <philipchen@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        Lee Jones <lee.jones@...aro.org>,
        Rajat Jain <rajatja@...gle.com>, linux-input@...r.kernel.org
Subject: [PATCH 3/3] Input: cros-ec-keyb - Expose function row physical map to userspace

The top-row keys in a keyboard usually have dual functionalities.
E.g. A function key "F1" is also an action key "Browser back".

Therefore, when an application receives an action key code from
a top-row key press, the application needs to know how to correlate
the action key code with the function key code and do the conversion
whenever necessary.

Since the userpace already knows the key scanlines (row/column)
associated with a received key code. Essentially, the userspace only
needs a mapping between the key row/column and the matching physical
location in the top row.

This patch enhances the cros-ec-keyb driver to create such a mapping and
expose it to userspace in the form of a function-row-physmap attribute.
The attribute would be a space separated ordered list of row/column codes,
for the keys in the function row, in left-to-right order.

The attribute will only be present when cros-ec-keyb sends action key
codes for the top-row keys, otherwise the attribute shall not be
visible.

Signed-off-by: Philip Chen <philipchen@...omium.org>
---

 drivers/input/keyboard/cros_ec_keyb.c | 59 +++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
index c997ec5c5d469..4f2f98bb14663 100644
--- a/drivers/input/keyboard/cros_ec_keyb.c
+++ b/drivers/input/keyboard/cros_ec_keyb.c
@@ -658,6 +658,56 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
 	return 0;
 }
 
+static ssize_t function_row_physmap_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	ssize_t size = 0;
+	u8 i;
+	u16 code;
+	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
+
+	if (!ckdev->num_function_row_keys)
+		return 0;
+
+	for (i = 0; i < ckdev->num_function_row_keys; i++) {
+		code = MATRIX_SCAN_CODE(top_row_key_pos[i].row,
+					top_row_key_pos[i].col,
+					ckdev->row_shift);
+		size += scnprintf(buf + size, PAGE_SIZE - size, "%02X ", code);
+	}
+	size += scnprintf(buf + size, PAGE_SIZE - size, "\n");
+
+	return size;
+}
+
+static DEVICE_ATTR_RO(function_row_physmap);
+
+static struct attribute *cros_ec_keyb_attrs[] = {
+	&dev_attr_function_row_physmap.attr,
+	NULL,
+};
+
+static umode_t cros_ec_keyb_attr_is_visible(struct kobject *kobj,
+					    struct attribute *attr,
+					    int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
+
+	if (attr == &dev_attr_function_row_physmap.attr &&
+	    !ckdev->num_function_row_keys)
+		return 0;
+
+	return attr->mode;
+}
+
+static const struct attribute_group cros_ec_keyb_attr_group = {
+	.is_visible = cros_ec_keyb_attr_is_visible,
+	.attrs = cros_ec_keyb_attrs,
+};
+
+
 static int cros_ec_keyb_probe(struct platform_device *pdev)
 {
 	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
@@ -688,6 +738,12 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	err = sysfs_create_group(&dev->kobj, &cros_ec_keyb_attr_group);
+	if (err) {
+		dev_err(dev, "failed to create attributes. err=%d\n", err);
+		return err;
+	}
+
 	ckdev->notifier.notifier_call = cros_ec_keyb_work;
 	err = blocking_notifier_chain_register(&ckdev->ec->event_notifier,
 					       &ckdev->notifier);
@@ -703,6 +759,9 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
 static int cros_ec_keyb_remove(struct platform_device *pdev)
 {
 	struct cros_ec_keyb *ckdev = dev_get_drvdata(&pdev->dev);
+	struct device *dev = &pdev->dev;
+
+	sysfs_remove_group(&dev->kobj, &cros_ec_keyb_attr_group);
 
 	blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
 					   &ckdev->notifier);
-- 
2.26.2