platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

Unfortunately the SMOxxxx ACPI device does not contain the i2c-address
of the accelerometer. So a DMI product-name to address mapping table
is used.

Add support to have the kernel probe for the i2c-address for models
which are not on the list.

The new probing code sits behind a new probe_i2c_addr module parameter,
which is disabled by default because probing might be dangerous.

Link: https://lore.kernel.org/linux-i2c/4820e280-9ca4-4d97-9d21-059626161bfc@molgen.mpg.de/
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20250106123259.45970-1-hdegoede@redhat.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

1 files changed, 52 insertions, 4 deletions

diff --git a/drivers/platform/x86/dell/dell-lis3lv02d.c b/drivers/platform/x86/dell/dell-lis3lv02d.c
index d2b34e10c5eb..c1596858dda6 100644
--- a/drivers/platform/x86/dell/dell-lis3lv02d.c
+++ b/drivers/platform/x86/dell/dell-lis3lv02d.c
@@ -15,6 +15,8 @@
 #include <linux/workqueue.h>
 #include "dell-smo8800-ids.h"
 
+#define LIS3_WHO_AM_I 0x0f
+
 #define DELL_LIS3LV02D_DMI_ENTRY(product_name, i2c_addr)                 \
 	{                                                                \
 		.matches = {                                             \
@@ -57,6 +59,42 @@ static u8 i2c_addr;
 static struct i2c_client *i2c_dev;
 static bool notifier_registered;
 
+static bool probe_i2c_addr;
+module_param(probe_i2c_addr, bool, 0444);
+MODULE_PARM_DESC(probe_i2c_addr, "Probe the i801 I2C bus for the accelerometer on models where the address is unknown, this may be dangerous.");
+
+static int detect_lis3lv02d(struct i2c_adapter *adap, unsigned short addr)
+{
+	union i2c_smbus_data smbus_data;
+	int err;
+
+	dev_info(&adap->dev, "Probing for lis3lv02d on address 0x%02x\n", addr);
+
+	err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, LIS3_WHO_AM_I,
+			     I2C_SMBUS_BYTE_DATA, &smbus_data);
+	if (err < 0)
+		return 0; /* Not found */
+
+	/* valid who-am-i values are from drivers/misc/lis3lv02d/lis3lv02d.c */
+	switch (smbus_data.byte) {
+	case 0x32:
+	case 0x33:
+	case 0x3a:
+	case 0x3b:
+		break;
+	default:
+		dev_warn(&adap->dev, "Unknown who-am-i register value 0x%02x\n",
+			 smbus_data.byte);
+		return 0; /* Not found */
+	}
+
+	dev_info(&adap->dev,
+		 "Detected lis3lv02d on address 0x%02x, please report this upstream to platform-driver-x86@vger.kernel.org so that a quirk can be added\n",
+		 addr);
+
+	return 1; /* Found */
+}
+
 static bool i2c_adapter_is_main_i801(struct i2c_adapter *adap)
 {
 	/*
@@ -97,10 +135,18 @@ static void instantiate_i2c_client(struct work_struct *work)
 	if (!adap)
 		return;
 
-	info.addr = i2c_addr;
 	strscpy(info.type, "lis3lv02d", I2C_NAME_SIZE);
 
-	i2c_dev = i2c_new_client_device(adap, &info);
+	if (i2c_addr) {
+		info.addr = i2c_addr;
+		i2c_dev = i2c_new_client_device(adap, &info);
+	} else {
+		/* First try address 0x29 (most used) and then try 0x1d */
+		static const unsigned short addr_list[] = { 0x29, 0x1d, I2C_CLIENT_END };
+
+		i2c_dev = i2c_new_scanned_device(adap, &info, addr_list, detect_lis3lv02d);
+	}
+
 	if (IS_ERR(i2c_dev)) {
 		dev_err(&adap->dev, "error %ld registering i2c_client\n", PTR_ERR(i2c_dev));
 		i2c_dev = NULL;
@@ -169,12 +215,14 @@ static int __init dell_lis3lv02d_init(void)
 	put_device(dev);
 
 	lis3lv02d_dmi_id = dmi_first_match(lis3lv02d_devices);
-	if (!lis3lv02d_dmi_id) {
+	if (!lis3lv02d_dmi_id && !probe_i2c_addr) {
 		pr_warn("accelerometer is present on SMBus but its address is unknown, skipping registration\n");
+		pr_info("Pass dell_lis3lv02d.probe_i2c_addr=1 on the kernel command line to probe, this may be dangerous!\n");
 		return 0;
 	}
 
-	i2c_addr = (long)lis3lv02d_dmi_id->driver_data;
+	if (lis3lv02d_dmi_id)
+		i2c_addr = (long)lis3lv02d_dmi_id->driver_data;
 
 	/*
 	 * Register i2c-bus notifier + queue initial scan for lis3lv02d