Hi Pali, On 6/24/24 8:21 PM, Pali Rohár wrote: > On Monday 24 June 2024 13:15:18 Hans de Goede wrote: >> 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> > > My comments from the previous version still apply there. There is no > dangerous warning neither in parameter name and its description, there > is no warning once the parameter was specified. I have added the same "this may be dangerous" text from: pr_info("Pass dell_lis3lv02d.probe_i2c_addr=1 on the kernel commandline to probe, this may be dangerous!\n"); to the MODULE_PARM_DESC() now too (for v5). > And there is missing > information from Dell how it is going to be handled for new > machines. So first ask Dell about the current state and future. As mentioned before Dell is on the Cc. And I no longer have any direct contacts inside Dell. If you know anyone inside Dell feel free to email them about this. Regards, Hans >> --- >> 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 >> >
