[PATCH] i2c: i2c-gpio: add support for i2c-gpio,sda-output-only

[Alex Shumsky]

Some I2C slave devices are read-only and don't even answer with NACK.
For example FD65x segment LED controllers.
Make them usable with i2c-gpio,sda-output-only that are already supported
by Linux 6.3+.

Signed-off-by: Alex Shumsky <alexthreed at gmail.com>
---

 doc/device-tree-bindings/i2c/i2c-gpio.txt |  2 ++
 drivers/i2c/i2c-gpio.c                    | 10 ++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/doc/device-tree-bindings/i2c/i2c-gpio.txt b/doc/device-tree-bindings/i2c/i2c-gpio.txt
index b06b829933..bb00854f33 100644
--- a/doc/device-tree-bindings/i2c/i2c-gpio.txt
+++ b/doc/device-tree-bindings/i2c/i2c-gpio.txt
@@ -20,6 +20,8 @@ Optional:
    Run deblocking sequence when the driver gets probed.
 * i2c-gpio,scl-output-only;
    Set if SCL is an output only
+* i2c-gpio,sda-output-only;
+   Set if SDA is an output only
 
 Example:
 
diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c
index e0a575fb4a..00aef40e34 100644
--- a/drivers/i2c/i2c-gpio.c
+++ b/drivers/i2c/i2c-gpio.c
@@ -101,7 +101,7 @@ static int i2c_gpio_read_bit(struct i2c_gpio_bus *bus, int delay)
 
 	bus->set_scl(bus, 1);
 	udelay(delay);
-	value = bus->get_sda(bus);
+	value = bus->get_sda ? bus->get_sda(bus) : 0;
 	udelay(delay);
 	bus->set_scl(bus, 0);
 	udelay(2 * delay);
@@ -256,6 +256,9 @@ static int i2c_gpio_read_data(struct i2c_gpio_bus *bus, uchar chip,
 {
 	unsigned int delay = bus->udelay;
 
+	if (!bus->get_sda)
+		return -EOPNOTSUPP;
+
 	debug("%s: chip %x buffer: %p len %d\n", __func__, chip, buffer, len);
 
 	while (len-- > 0)
@@ -353,7 +356,10 @@ static int i2c_gpio_of_to_plat(struct udevice *dev)
 	bus->udelay = dev_read_u32_default(dev, "i2c-gpio,delay-us",
 					   DEFAULT_UDELAY);
 
-	bus->get_sda = i2c_gpio_sda_get;
+	if (dev_read_bool(dev, "i2c-gpio,sda-output-only"))
+		bus->get_sda = NULL;
+	else
+		bus->get_sda = i2c_gpio_sda_get;
 	bus->set_sda = i2c_gpio_sda_set;
 	if (dev_read_bool(dev, "i2c-gpio,scl-output-only"))
 		bus->set_scl = i2c_gpio_scl_set_output_only;
-- 
2.34.1