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@xxxxxxxxxxxxx/ Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/platform/x86/dell/dell-lis3lv02d.c | 133 ++++++++++++++++++++- 1 file changed, 131 insertions(+), 2 deletions(-) diff --git a/drivers/platform/x86/dell/dell-lis3lv02d.c b/drivers/platform/x86/dell/dell-lis3lv02d.c index a7409db0505b..173615fd2646 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 +59,121 @@ static const struct dmi_system_id *lis3lv02d_dmi_id; 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 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 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); + pr_warn("I2C safety check for address 0x%02x failed, skipping\n", addr); + return -ENODEV; +} + +static int detect_lis3lv02d(struct i2c_adapter *adap, u8 addr, + struct i2c_board_info *info) +{ + union i2c_smbus_data smbus_data; + int err; + + pr_info("Probing for lis3lv02d on address 0x%02x\n", addr); + err = i2c_safety_check(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) { + pr_warn("Failed to read who-am-i register: %d\n", err); + return err; + } + + /* 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 -ENODEV; + } + + pr_debug("Detected lis3lv02d on address 0x%02x\n", addr); + info->addr = addr; + return 0; +} + static bool i2c_adapter_is_main_i801(struct i2c_adapter *adap) { /* @@ -93,7 +210,17 @@ static void instantiate_i2c_client(struct work_struct *work) if (!adap) return; - info.addr = (long)lis3lv02d_dmi_id->driver_data; + if (lis3lv02d_dmi_id) { + info.addr = (long)lis3lv02d_dmi_id->driver_data; + } else { + /* First try address 0x29 (most used) and then try 0x1d */ + if (detect_lis3lv02d(adap, 0x29, &info) != 0 && + detect_lis3lv02d(adap, 0x1d, &info) != 0) { + pr_warn("failed to probe for lis3lv02d I2C address\n"); + goto out_put_adapter; + } + } + strscpy(info.type, "lis3lv02d", I2C_NAME_SIZE); i2c_dev = i2c_new_client_device(adap, &info); @@ -104,6 +231,7 @@ static void instantiate_i2c_client(struct work_struct *work) pr_debug("registered lis3lv02d on address 0x%02x\n", info.addr); } +out_put_adapter: i2c_put_adapter(adap); } static DECLARE_WORK(i2c_work, instantiate_i2c_client); @@ -166,8 +294,9 @@ 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; } -- 2.45.1
