[PATCH v2] Input: goodix-berlin - Add sysfs interface for reading and writing touch IC registers

[Charles Wang <charles.goodix@gmail.com>]

Export a sysfs interface that would allow reading and writing touchscreen
IC registers. With this interface many things can be done in usersapce
such as firmware updates. An example tool that utilizes this interface
for performing firmware updates can be found at [1].

[1] https://github.com/goodix/fwupdate_for_berlin_linux

Signed-off-by: Charles Wang <charles.goodix@gmail.com>
---
Changes in v2:
- use dev_groups to manager device attributes.
- use dev_get_regmap to make show/store functions generic.
- v1: https://lore.kernel.org/all/20240506114752.47204-1-charles.goodix@gmail.com/
---
 drivers/input/touchscreen/goodix_berlin.h     |  1 +
 .../input/touchscreen/goodix_berlin_core.c    | 42 +++++++++++++++++++
 drivers/input/touchscreen/goodix_berlin_i2c.c |  1 +
 drivers/input/touchscreen/goodix_berlin_spi.c |  1 +
 4 files changed, 45 insertions(+)

diff --git a/drivers/input/touchscreen/goodix_berlin.h b/drivers/input/touchscreen/goodix_berlin.h
index 1fd77eb69..38b6f9ddb 100644
--- a/drivers/input/touchscreen/goodix_berlin.h
+++ b/drivers/input/touchscreen/goodix_berlin.h
@@ -20,5 +20,6 @@ int goodix_berlin_probe(struct device *dev, int irq, const struct input_id *id,
 			struct regmap *regmap);
 
 extern const struct dev_pm_ops goodix_berlin_pm_ops;
+extern const struct attribute_group *goodix_berlin_groups[];
 
 #endif
diff --git a/drivers/input/touchscreen/goodix_berlin_core.c b/drivers/input/touchscreen/goodix_berlin_core.c
index e7b41a926..e90fccfc4 100644
--- a/drivers/input/touchscreen/goodix_berlin_core.c
+++ b/drivers/input/touchscreen/goodix_berlin_core.c
@@ -672,6 +672,48 @@ static void goodix_berlin_power_off_act(void *data)
 	goodix_berlin_power_off(cd);
 }
 
+static ssize_t registers_read(struct file *filp, struct kobject *kobj,
+	struct bin_attribute *bin_attr, char *buf, loff_t off, size_t count)
+{
+	struct regmap *regmap;
+	int error;
+
+	regmap = dev_get_regmap(kobj_to_dev(kobj), NULL);
+	error = regmap_raw_read(regmap, (unsigned int)off,
+				buf, count);
+
+	return error ? error : count;
+}
+
+static ssize_t registers_write(struct file *filp, struct kobject *kobj,
+	struct bin_attribute *bin_attr, char *buf, loff_t off, size_t count)
+{
+	struct regmap *regmap;
+	int error;
+
+	regmap = dev_get_regmap(kobj_to_dev(kobj), NULL);
+	error = regmap_raw_write(regmap, (unsigned int)off,
+				 buf, count);
+
+	return error ? error : count;
+}
+
+BIN_ATTR_RW(registers, 0);
+
+static struct bin_attribute *goodix_berlin_bin_attrs[] = {
+	&bin_attr_registers,
+	NULL,
+};
+
+static const struct attribute_group goodix_berlin_attr_group = {
+	.bin_attrs = goodix_berlin_bin_attrs,
+};
+
+const struct attribute_group *goodix_berlin_groups[] = {
+	&goodix_berlin_attr_group,
+	NULL,
+};
+
 int goodix_berlin_probe(struct device *dev, int irq, const struct input_id *id,
 			struct regmap *regmap)
 {
diff --git a/drivers/input/touchscreen/goodix_berlin_i2c.c b/drivers/input/touchscreen/goodix_berlin_i2c.c
index 6ed9aa808..b5f48315c 100644
--- a/drivers/input/touchscreen/goodix_berlin_i2c.c
+++ b/drivers/input/touchscreen/goodix_berlin_i2c.c
@@ -64,6 +64,7 @@ static struct i2c_driver goodix_berlin_i2c_driver = {
 		.name = "goodix-berlin-i2c",
 		.of_match_table = goodix_berlin_i2c_of_match,
 		.pm = pm_sleep_ptr(&goodix_berlin_pm_ops),
+		.dev_groups = goodix_berlin_groups,
 	},
 	.probe = goodix_berlin_i2c_probe,
 	.id_table = goodix_berlin_i2c_id,
diff --git a/drivers/input/touchscreen/goodix_berlin_spi.c b/drivers/input/touchscreen/goodix_berlin_spi.c
index 4cc557da0..fe5739097 100644
--- a/drivers/input/touchscreen/goodix_berlin_spi.c
+++ b/drivers/input/touchscreen/goodix_berlin_spi.c
@@ -167,6 +167,7 @@ static struct spi_driver goodix_berlin_spi_driver = {
 		.name = "goodix-berlin-spi",
 		.of_match_table = goodix_berlin_spi_of_match,
 		.pm = pm_sleep_ptr(&goodix_berlin_pm_ops),
+		.dev_groups = goodix_berlin_groups,
 	},
 	.probe = goodix_berlin_spi_probe,
 	.id_table = goodix_berlin_spi_ids,
-- 
2.43.0