Re: [PATCH 5/8] mfd: aaeon: Add SRG-IMX8PL MCU driver

On Fri, 12 Dec 2025, Thomas Perrot (Schneider Electric) wrote:

Add Multi-Function Device (MFD) driver for the Aaeon SRG-IMX8PL

Drop all mentions of MFD.  It's not a real thing - we made it up.

Is that an exhaustive list of sub-devices?

Not MFD - describe the actual device.

+ *
+ * Copyright (C) 2025 Bootlin

Has it been agreed that you would hold the copyright to this?

+ * Author: Jérémie Dautheribes [off-list ref]
+ * Author: Thomas Perrot [off-list ref]
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/aaeon-mcu.h>

Alphabetical.

+#define AAEON_MCU_GET_FW_VERSION 0x76

Is that what the register is called in the datasheet?

The GET part is odd.

+static struct mfd_cell aaeon_mcu_devs[] = {
+	{
+		.name = "aaeon-mcu-wdt",
+		.of_compatible = "aaeon,srg-imx8pl-wdt",
+	},
+	{
+		.name = "aaeon-mcu-gpio",
+		.of_compatible = "aaeon,srg-imx8pl-gpio",
+	},
+};
+
+static int aaeon_mcu_print_fw_version(struct i2c_client *client)
+{
+	u8 cmd[3], version[2];
+	int ret;
+
+	/* Major version number */
+	cmd[0] = AAEON_MCU_GET_FW_VERSION;
+	cmd[1] = 0x00;
+	cmd[2] = 0x00;
+
+	ret = aaeon_mcu_i2c_xfer(client, cmd, 3, &version[0], 1);
+	if (ret < 0)
+		return ret;
+
+	/* Minor version number */
+	cmd[0] = AAEON_MCU_GET_FW_VERSION;
+	cmd[1] = 0x01;
+	/* cmd[2] = 0x00; */
+
+	ret = aaeon_mcu_i2c_xfer(client, cmd, 3, &version[1], 1);
+	if (ret < 0)
+		return ret;
+
+	dev_info(&client->dev, "firmware version: v%d.%d\n",
+		 version[0], version[1]);

What do you expect a user to do with this information?

Let's cut the debug cruft - you can add it again locally if you need to debug.

+
+	return 0;
+}

Besides providing a questionable print, you don't seem to be doing
anything with this information - is it needed at all?

+static int aaeon_mcu_probe(struct i2c_client *client)
+{
+	struct aaeon_mcu_dev *mcu;
+	int ret;
+
+	mcu = devm_kzalloc(&client->dev, sizeof(*mcu), GFP_KERNEL);
+	if (!mcu)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, mcu);

+	mcu->dev = &client->dev;
+	mcu->i2c_client = client;

How do you expect to be able to 'get' this data back if you do not have
the 'dev' or the 'client'?

+	mutex_init(&mcu->i2c_lock);
+
+	ret = aaeon_mcu_print_fw_version(client);
+	if (ret) {
+		dev_err(&client->dev, "unable to read firmware version\n");
+		return ret;
+	}
+
+	return devm_mfd_add_devices(mcu->dev, PLATFORM_DEVID_NONE, aaeon_mcu_devs,
+				    ARRAY_SIZE(aaeon_mcu_devs), NULL, 0, NULL);
+}
+
+int aaeon_mcu_i2c_xfer(struct i2c_client *client,
+		       const u8 *cmd, int cmd_len,
+		       u8 *rsp, int rsp_len)
+{
+	struct aaeon_mcu_dev *mcu = i2c_get_clientdata(client);
+	int ret;
+
+	mutex_lock(&mcu->i2c_lock);
+
+	ret = i2c_master_send(client, cmd, cmd_len);
+	if (ret < 0)
+		goto unlock;
+
+	ret = i2c_master_recv(client, rsp, rsp_len);
+	if (ret < 0)
+		goto unlock;

Isn't this all very generic?

I wonder how many similar functions there are in the kernel.

Worth making this global?

+	if (ret != rsp_len) {
+		dev_err(&client->dev,
+			"i2c recv count error (expected: %d, actual: %d)\n",
+			rsp_len, ret);
+		ret = -EIO;
+		goto unlock;
+	}
+
+	ret = 0;
+
+unlock:
+	mutex_unlock(&mcu->i2c_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(aaeon_mcu_i2c_xfer);

This should be much further up.  At least above probe - perhaps higher.

+static const struct of_device_id aaeon_mcu_of_match[] = {
+	{ .compatible = "aaeon,srg-imx8pl-mcu" },
+	{},
+};
+

Remove this line.

+MODULE_DEVICE_TABLE(of, aaeon_mcu_of_match);
+
+static struct i2c_driver aaeon_mcu_driver = {
+	.driver = {
+		.name = "aaeon_mcu",
+		.of_match_table = aaeon_mcu_of_match,
+	},
+	.probe = aaeon_mcu_probe,
+};
+

And this one.

+module_i2c_driver(aaeon_mcu_driver);
+
+MODULE_DESCRIPTION("Aaeon MCU MFD Driver");

Not MFD.

+MODULE_AUTHOR("Jérémie Dautheribes");

Email?

-- 
Lee Jones [李琼斯]