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.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/platform/x86/dell/dell-smo8800.c | 152 ++++++++++++++++++++++-
1 file changed, 147 insertions(+), 5 deletions(-)
diff --git a/drivers/platform/x86/dell/dell-smo8800.c b/drivers/platform/x86/dell/dell-smo8800.c
index 4c79b2599d96..d64d200e927a 100644
--- a/drivers/platform/x86/dell/dell-smo8800.c
+++ b/drivers/platform/x86/dell/dell-smo8800.c
@@ -10,6 +10,7 @@
*/
#define DRIVER_NAME "smo8800"
+#define LIS3_WHO_AM_I 0x0f
#include <linux/device/bus.h>
#include <linux/dmi.h>
@@ -25,6 +26,10 @@
#include <linux/uaccess.h>
#include <linux/workqueue.h>
+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");
+
struct smo8800_device {
u32 irq; /* acpi device irq */
atomic_t counter; /* count after last read */
@@ -225,6 +230,130 @@ static const struct dmi_system_id smo8800_lis3lv02d_devices[] = {
{ }
};
+/*
+ * This is the kernel version of the single register device sanity checks from
+ * the i2c_safety_check function from lm_sensors sensor-detect script:
+ * This is meant to prevent access to 1-register-only devices,
+ * which are designed to be accessed with SMBus receive byte and SMBus send
+ * byte transactions (i.e. short reads and short writes) and treat SMBus
+ * read byte as a real write followed by a read. The device detection
+ * routines would write random values to the chip with possibly very nasty
+ * results for the hardware. Note that this function won't catch all such
+ * chips, as it assumes that reads and writes relate to the same register,
+ * but that's the best we can do.
+ */
+static int i2c_safety_check(struct device *dev, struct i2c_adapter *adap, u8 addr)
+{
+ union i2c_smbus_data smbus_data;
+ int err;
+ u8 data;
+
+ /*
+ * First receive a byte from the chip, and remember it. This
+ * also checks if there is a device at the address at all.
+ */
+ err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+ I2C_SMBUS_BYTE, &smbus_data);
+ if (err < 0)
+ return err;
+
+ data = smbus_data.byte;
+
+ /*
+ * Receive a byte again; very likely to be the same for
+ * 1-register-only devices.
+ */
+ err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+ I2C_SMBUS_BYTE, &smbus_data);
+ if (err < 0)
+ return err;
+
+ if (smbus_data.byte != data)
+ return 0; /* Not a 1-register-only device. */
+
+ /*
+ * Then try a standard byte read, with a register offset equal to
+ * the read byte; for 1-register-only device this should read
+ * the same byte value in return.
+ */
+ err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, data,
+ I2C_SMBUS_BYTE_DATA, &smbus_data);
+ if (err < 0)
+ return err;
+
+ if (smbus_data.byte != data)
+ return 0; /* Not a 1-register-only device. */
+
+ /*
+ * Then try a standard byte read, with a slightly different register
+ * offset; this should again read the register offset in return.
+ */
+ err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, data ^ 0x01,
+ I2C_SMBUS_BYTE_DATA, &smbus_data);
+ if (err < 0)
+ return err;
+
+ if (smbus_data.byte != (data ^ 0x01))
+ return 0; /* Not a 1-register-only device. */
+
+ /*
+ * Apparently this is a 1-register-only device, restore the original
+ * register value and leave it alone.
+ */
+ i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, data,
+ I2C_SMBUS_BYTE, NULL);
+ dev_warn(dev, "I2C safety check for address 0x%02x failed, skipping\n", addr);
+ return -ENODEV;
+}
+
+static int smo8800_detect_accel(struct smo8800_device *smo8800,
+ struct i2c_adapter *adap, u8 addr,
+ struct i2c_board_info *info, bool probe)
+{
+ union i2c_smbus_data smbus_data;
+ const char *type;
+ int err;
+
+ if (probe) {
+ dev_info(smo8800->dev, "Probing for accelerometer on address 0x%02x\n", addr);
+ err = i2c_safety_check(smo8800->dev, adap, addr);
+ if (err < 0)
+ return err;
+ }
+
+ err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, LIS3_WHO_AM_I,
+ I2C_SMBUS_BYTE_DATA, &smbus_data);
+ if (err < 0) {
+ dev_warn(smo8800->dev, "Failed to read who-am-i register: %d\n", err);
+ return err;
+ }
+
+ /* who-am-i register mappings from drivers/misc/lis3lv02d/lis3lv02d.c */
+ switch (smbus_data.byte) {
+ case 0x32:
+ type = "lis331dlh";
+ break;
+ case 0x33:
+ type = "lis2de12"; /* LIS3DC / HP3DC in drivers/misc/lis3lv02d/lis3lv02d.c */
+ break;
+ case 0x3a:
+ type = "lis3lv02dl_accel";
+ break;
+ case 0x3b:
+ type = "lis302dl";
+ break;
+ default:
+ dev_warn(smo8800->dev, "Unknown who-am-i register value 0x%02x\n",
+ smbus_data.byte);
+ return -ENODEV;
+ }
+
+ dev_dbg(smo8800->dev, "Detected %s accelerometer on address 0x%02x\n", type, addr);
+ strscpy(info->type, "lis3lv02d", I2C_NAME_SIZE);
+ info->addr = addr;
+ return 0;
+}
+
static int smo8800_find_i801(struct device *dev, void *data)
{
struct i2c_adapter *adap, **adap_ret = data;
@@ -247,6 +376,7 @@ static void smo8800_instantiate_i2c_client(struct work_struct *work)
const struct dmi_system_id *lis3lv02d_dmi_id;
struct i2c_board_info info = { };
struct i2c_adapter *adap = NULL;
+ int err;
if (smo8800->i2c_dev)
return;
@@ -256,11 +386,22 @@ static void smo8800_instantiate_i2c_client(struct work_struct *work)
return;
lis3lv02d_dmi_id = dmi_first_match(smo8800_lis3lv02d_devices);
- if (!lis3lv02d_dmi_id)
+ if (lis3lv02d_dmi_id) {
+ info.addr = (long)lis3lv02d_dmi_id->driver_data;
+ /* Always detect the accel-type, this also checks the accel is actually there */
+ err = smo8800_detect_accel(smo8800, adap, info.addr, &info, false);
+ if (err)
+ goto out_put_adapter;
+ } else if (probe_i2c_addr) {
+ /* First try address 0x29 (most used) and then try 0x1d */
+ if (smo8800_detect_accel(smo8800, adap, 0x29, &info, true) != 0 &&
+ smo8800_detect_accel(smo8800, adap, 0x1d, &info, true) != 0) {
+ dev_warn(smo8800->dev, "failed to probe for lis3lv02d I2C address\n");
+ goto out_put_adapter;
+ }
+ } else {
goto out_put_adapter;
-
- info.addr = (long)lis3lv02d_dmi_id->driver_data;
- strscpy(info.type, "lis3lv02d", I2C_NAME_SIZE);
+ }
smo8800->i2c_dev = i2c_new_client_device(adap, &info);
if (IS_ERR(smo8800->i2c_dev)) {
@@ -357,7 +498,7 @@ static int smo8800_probe(struct platform_device *device)
smo8800->irq);
}
- if (dmi_check_system(smo8800_lis3lv02d_devices)) {
+ if (dmi_check_system(smo8800_lis3lv02d_devices) || probe_i2c_addr) {
/*
* Register i2c-bus notifier + queue initial scan for lis3lv02d
* i2c_client instantiation.
@@ -370,6 +511,7 @@ static int smo8800_probe(struct platform_device *device)
} else {
dev_warn(&device->dev,
"lis3lv02d accelerometer is present on SMBus but its address is unknown, skipping registration\n");
+ dev_info(&device->dev, "Pass dell_smo8800.probe_i2c_addr=1 on the kernel commandline to probe, this may be dangerous!\n");
if (!smo8800->irq)
return -ENODEV;
}
--
2.45.1
