[PATCH 4/4] pinctrl: mcp23s08: work around GPIO line naming

[Jan Kundrát <jan.kundrat@xxxxxxxxx>]

This driver is a bit weird because it can hide several gpio_chip
instances underneath a single SPI slave. One cannot put the
gpio-line-names DT stanza directly to the SPI slave when the
spi-present-mask has more than one bit set.

I'm making up the `gpio-bank` DT child name as well as its `address`
property. We need something to match the DT entries with the SPI
address.

Signed-off-by: Jan Kundrát <jan.kundrat@xxxxxxxxx>
---
 .../bindings/pinctrl/pinctrl-mcp23s08.txt     | 35 +++++++++++++++++++
 drivers/pinctrl/pinctrl-mcp23s08.c            | 12 +++++++
 2 files changed, 47 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
index a5a8322a31bd..7573df69ccea 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
@@ -142,3 +142,38 @@ gpio21: gpio@21 {
 		bias-pull-up;
 	};
 };
+
+Line naming
+===========
+
+Because several gpio_chip instances are hidden below a single device tree
+node, it is necessary to split the names into several child nodes. Ensure
+that the configured addresses match those in the microchip,spi-present-mask:
+
+gpio@0 {
+        compatible = "microchip,mcp23s17";
+        gpio-controller;
+        #gpio-cells = <2>;
+	/* this bitmask has bits #0 (0x01) and #2 (0x04) set */
+        spi-present-mask = <0x05>;
+        reg = <0>;
+        spi-max-frequency = <1000000>;
+
+	gpio-bank@1 {
+		address = <0>;
+		gpio-line-names =
+			"GPA0",
+			"GPA1",
+			...
+			"GPA7",
+			"GPB0",
+			"GPB1",
+			...
+			"GPB7";
+	};
+
+	gpio-bank@2 {
+		address = <2>;
+		gpio-line-names = ...
+	};
+};
diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index bbef9833edb8..c4fac4e1de71 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -16,6 +16,7 @@
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinconf.h>
 #include <linux/pinctrl/pinconf-generic.h>
+#include "../gpio/gpiolib.h"
 
 /*
  * MCP types supported by driver
@@ -1086,6 +1087,7 @@ static int mcp23s08_probe(struct spi_device *spi)
 	int				status, type;
 	unsigned			ngpio = 0;
 	const struct			of_device_id *match;
+	struct device_node		*np;
 
 	match = of_match_device(of_match_ptr(mcp23s08_spi_of_match), &spi->dev);
 	if (match)
@@ -1148,6 +1150,16 @@ static int mcp23s08_probe(struct spi_device *spi)
 		if (pdata->base != -1)
 			pdata->base += data->mcp[addr]->chip.ngpio;
 		ngpio += data->mcp[addr]->chip.ngpio;
+
+		for_each_available_child_of_node(spi->dev.of_node, np) {
+			u32 chip_addr;
+			status = of_property_read_u32(np, "address", &chip_addr);
+			if (status)
+				continue;
+			if (chip_addr != addr)
+				continue;
+			devprop_gpiochip_set_names(&data->mcp[addr]->chip, of_fwnode_handle(np));
+		}
 	}
 	data->ngpio = ngpio;
 
-- 
2.17.1


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