[PATCH v3 2/2] Input: atmel_mxt_ts: Allow per-machine config via DT compatible

[Hendrik Noack]

The Atmel maXTouch config is machine-dependent, different panels and
layouts require different configs even when the same controller and
firmware is used.

Extend the driver to support per-machine config files keyed by the device
tree compatible prop. For DT-based systems, the driver now looks up the
primary compatible of the machine and searches for a config file named:

  atmel/maxtouch.<compatible>.cfg

If such a file exists, it is used as the machine-specific config. If the
system is not DT-based or if the per-machine file is not present, the
driver reverts to the original behaviour and searches for a config file
named:

  maxtouch.cfg

Signed-off-by: Hendrik Noack <hendrik-noack@xxxxxx>
---
Changes in v2:
- fix leak of fw_name (thanks sashiko.dev)
- adopt to added patch

---
Changes in v3:
- fix bypass of of_node_put (thanks sashiko.dev)

---
 drivers/input/touchscreen/atmel_mxt_ts.c | 69 +++++++++++++++++++++---
 1 file changed, 63 insertions(+), 6 deletions(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index a88dc7e6827c..0081fa5c7802 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -36,7 +36,9 @@
 
 /* Firmware files */
 #define MXT_FW_NAME		"maxtouch.fw"
-#define MXT_CFG_NAME		"maxtouch.cfg"
+#define MXT_CFG_FOLDER		"atmel"
+#define MXT_CFG_NAME		"maxtouch"
+#define MXT_CFG_EXTENSION	".cfg"
 #define MXT_CFG_MAGIC		"OBP_RAW V1"
 
 /* Registers */
@@ -2232,6 +2234,64 @@ static void mxt_config_cb(const struct firmware *cfg, void *ctx)
 	complete(&data->config_completion);
 }
 
+static int mxt_invoke_config_loader(struct mxt_data *data, bool device_specific);
+
+static void mxt_board_config_cb(const struct firmware *cfg, void *ctx)
+{
+	if (!cfg) {
+		struct mxt_data *data = ctx;
+		int error;
+
+		error = mxt_invoke_config_loader(data, false);
+		/* request_firmware_nowait() succeeded and mxt_config_cb() will be called at end */
+		if (!error)
+			return;
+
+		dev_err(&data->client->dev, "Failed to invoke general config loader: %d\n", error);
+	}
+
+	mxt_config_cb(cfg, ctx);
+}
+
+static int mxt_invoke_config_loader(struct mxt_data *data, bool device_specific)
+{
+	struct device_node *root;
+	char *board_type = NULL;
+	char *fw_name;
+	void (*cb)(const struct firmware *fw, void *context);
+	int error;
+
+	/* Get first string of the machine compatible prop */
+	root = of_find_node_by_path("/");
+	if (device_specific && root) {
+		const char *tmp;
+
+		if (!of_property_read_string_index(root, "compatible", 0, &tmp))
+			board_type = kstrdup(tmp, GFP_KERNEL);
+	}
+	of_node_put(root);
+
+	if (board_type) {
+		/* get rid of '/' in the compatible string to be able to find the FW */
+		strreplace(board_type, '/', '-');
+
+		fw_name = kasprintf(GFP_KERNEL, "%s/%s.%s%s", MXT_CFG_FOLDER, MXT_CFG_NAME,
+				    board_type, MXT_CFG_EXTENSION);
+		cb = mxt_board_config_cb;
+		kfree(board_type);
+	} else {
+		fw_name = kasprintf(GFP_KERNEL, "%s%s", MXT_CFG_NAME, MXT_CFG_EXTENSION);
+		cb = mxt_config_cb;
+	}
+	if (!fw_name)
+		return -ENOMEM;
+
+	error = request_firmware_nowait(THIS_MODULE, true, fw_name, &data->client->dev, GFP_KERNEL,
+					data, cb);
+	kfree(fw_name);
+	return error;
+}
+
 static int mxt_initialize(struct mxt_data *data)
 {
 	struct i2c_client *client = data->client;
@@ -2291,12 +2351,9 @@ static int mxt_initialize(struct mxt_data *data)
 		return -EBUSY;
 	}
 
-	error = request_firmware_nowait(THIS_MODULE, true, MXT_CFG_NAME,
-					&client->dev, GFP_KERNEL, data,
-					mxt_config_cb);
+	error = mxt_invoke_config_loader(data, true);
 	if (error) {
-		dev_err(&client->dev, "Failed to invoke firmware loader: %d\n",
-			error);
+		dev_err(&client->dev, "Failed to invoke config loader: %d\n", error);
 		complete(&data->config_completion);
 		return error;
 	}
-- 
2.43.0