From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 63E6482492; Sat, 22 Jun 2024 13:32:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719063161; cv=none; b=R9aV49SNEz0WVRx7y19NYAkOnWcl1+sejWdgLBONfuhQdasxsmHnhe2kIcIC5768o3XpjdHnD5bPncmPwrZ4pQThDjWNc95xjtBs34XYBjSWwVy8PAHIWnAckKghVGErd9tgx919gO8/FYkDr6dMbaNNJDJ4/UxdHFwOu8CjKG0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719063161; c=relaxed/simple; bh=UsI7DtPhAH24sCtEn38xtTefdjo8zVjhTDCD4JLAMLQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rTKju6lippak7qntQEYN2mD6m/zhP+/W51Vg4OqooE2df55btFxcKc7quC98zvtSyB3nzmqDS3fQjYNPqCHtG6OcEBZlhA83M5lNHZ4NVurgcAMhFqkcwmpDxq4mLsGFBb2PM1ZSngtD4Xho8xSlhZoCBOnJ5QobLg6gT6c6p2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PNOjjFli; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PNOjjFli" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79517C3277B; Sat, 22 Jun 2024 13:32:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719063160; bh=UsI7DtPhAH24sCtEn38xtTefdjo8zVjhTDCD4JLAMLQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PNOjjFli24Pm5DtTJEfxRy4uUfTfsg7cpPwzNh9VrSlwByi9NyYjhjwEvRKeuzC4W SeP1n3bckEx3tXgEv+9jCJ2XjLA3ZhR+ySV/l/Ely5UkWMAgrVQfBHC2qIYMqUeHYP DySESRpOliNcfWMilWZhz1tXsIoN3m3VEEMzpmo7Tdsr+g6B51lCE/UVmdeYB4FOM2 CWroS/9mlo8Jasi1VwZpw76uPXmRilGtZ3RPCe70m7gBOiWNpXS9LLMU0Ql0uxMmj7 CIIO/veYOnSE7Tde/RZV65Z95Zkiq0yh7GpaoApXP5CsK2E6LGNdViVYdBcjpmLNhe V+rjbvQ46+wyg== Received: by pali.im (Postfix) id AAAC464C; Sat, 22 Jun 2024 15:32:37 +0200 (CEST) Date: Sat, 22 Jun 2024 15:32:37 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Hans de Goede Cc: Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Andy Shevchenko , Paul Menzel , Wolfram Sang , eric.piel@tremplin-utc.net, Marius Hoch , Dell.Client.Kernel@dell.com, Kai Heng Feng , platform-driver-x86@vger.kernel.org, Jean Delvare , Andi Shyti , linux-i2c@vger.kernel.org Subject: Re: [PATCH v3 6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address Message-ID: <20240622133237.b5xsetcxnfu4vu6u@pali> References: <20240621122503.10034-1-hdegoede@redhat.com> <20240621122503.10034-7-hdegoede@redhat.com> Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240621122503.10034-7-hdegoede@redhat.com> User-Agent: NeoMutt/20180716 On Friday 21 June 2024 14:25:01 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. This is statement which I got from Dell for 10 years old Dell models. I have already stated that poking of address in kernel is a big risk specially for all current and any future dell hardware. Hiding it just under the kernel parameter is still a risk, specially as neither its name, nor description say that it is dangerous. But anyway, why this code is being introduced? Have you communicated with Dell about this problem? > 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 > --- > 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 > #include > @@ -25,6 +26,10 @@ > #include > #include > > +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 >