[PATCH v7 6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

Hans de Goede
2024-08-05T13:38:58Z

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.

At support to have the kernel probe for the i2c-address for modesl
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>
---
Changes in v6:
- Use i2c_new_scanned_device() instead of re-inventing it

Changes in v5:
- Add "this may be dangerous warning" to MODULE_PARM_DESC(probe_i2c_addr)
---
drivers/platform/x86/dell/dell-lis3lv02d.c | 52 ++++++++++++++++++++--
1 file changed, 48 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-lis3lv02d.c b/drivers/platform/x86/dell/dell-lis3lv02d.c
index ab02ad93758a..21390e6302a0 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 +59,38 @@ 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;
+
+ pr_info("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:
+ pr_warn("Unknown who-am-i register value 0x%02x\n", smbus_data.byte);
+ return 0; /* Not found */
+ }
+
+ pr_debug("Detected lis3lv02d on address 0x%02x\n", addr);
+ return 1; /* Found */
+}
+
static bool i2c_adapter_is_main_i801(struct i2c_adapter *adap)
{
/*
@@ -93,10 +127,18 @@ 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)) {
pr_err("error %ld registering i2c_client\n", PTR_ERR(i2c_dev));
i2c_dev = NULL;
@@ -167,12 +209,14 @@ 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 commandline 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
--
2.45.2