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From:   Philip Chen <philipchen@chromium.org>
To:     LKML <linux-kernel@vger.kernel.org>, dmitry.torokhov@gmail.com
Cc:     dianders@chromium.org, swboyd@chromium.org,
        Philip Chen <philipchen@chromium.org>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>,
        Lee Jones <lee.jones@linaro.org>, linux-input@vger.kernel.org
Subject: [PATCH v2 2/2] Input: cros-ec-keyb - Expose function row physical map to userspace
Date:   Mon,  4 Jan 2021 14:55:32 -0800
Message-Id: <20210104145523.v2.2.Ibe7d7d53c5b4fe72c60de90111ff763b53f38dbb@changeid>
In-Reply-To: <20210104145523.v2.1.I025fb861cd5fa0ef5286b7dce514728e9df7ae74@changeid>
References: <20210104145523.v2.1.I025fb861cd5fa0ef5286b7dce514728e9df7ae74@changeid>
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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 a left-to-right
order.

The attribute will only be present when the device has a custom design
for the top-row keys.

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

Changes in v2:
- create function-row-physmap file in sysfs by parsing
  `function-row-physmap` property from DT
- assume the device already has a correct keymap to reflect the custom
  top-row keys (if they exist)

 drivers/input/keyboard/cros_ec_keyb.c | 72 +++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
index b379ed7628781..06642e4ce9c63 100644
--- a/drivers/input/keyboard/cros_ec_keyb.c
+++ b/drivers/input/keyboard/cros_ec_keyb.c
@@ -27,6 +27,8 @@
 
 #include <asm/unaligned.h>
 
+#define MAX_NUM_TOP_ROW_KEYS   15
+
 /**
  * struct cros_ec_keyb - Structure representing EC keyboard device
  *
@@ -35,6 +37,7 @@
  * @row_shift: log2 or number of rows, rounded up
  * @keymap_data: Matrix keymap data used to convert to keyscan values
  * @ghost_filter: true to enable the matrix key-ghosting filter
+ * @has_custom_top_row_keys: true if the keyboard has custom top row keys
  * @valid_keys: bitmap of existing keys for each matrix column
  * @old_kb_state: bitmap of keys pressed last scan
  * @dev: Device pointer
@@ -49,6 +52,7 @@ struct cros_ec_keyb {
 	int row_shift;
 	const struct matrix_keymap_data *keymap_data;
 	bool ghost_filter;
+	bool has_custom_top_row_keys;
 	uint8_t *valid_keys;
 	uint8_t *old_kb_state;
 
@@ -587,6 +591,65 @@ 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;
+	u32 top_row_key_code[MAX_NUM_TOP_ROW_KEYS] = {0};
+	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
+
+	if (of_property_read_variable_u32_array(dev->of_node,
+						"function-row-physmap",
+						top_row_key_code,
+						0,
+						MAX_NUM_TOP_ROW_KEYS) > 0)
+		return 0;
+
+	ckdev->has_custom_top_row_keys = true;
+
+	for (i = 0; i < MAX_NUM_TOP_ROW_KEYS; i++) {
+		if (!top_row_key_code[i])
+			break;
+		code = MATRIX_SCAN_CODE(KEY_ROW(top_row_key_code[i]),
+					KEY_COL(top_row_key_code[i]),
+					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->has_custom_top_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);
@@ -617,6 +680,12 @@ 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);
@@ -632,6 +701,9 @@ 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