| Message ID | 20220728125435.3336618-3-potin.lai.pt@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | iio: humidity: hdc100x: add manufacturer and device ID check | expand |
On Thu, Jul 28, 2022 at 3:32 PM Potin Lai <potin.lai.pt@gmail.com> wrote: > > Add manufacturer and device ID checking during probe, and skip the > checking if chip model not supported. > > Supported: > - HDC1000 > - HDC1010 > - HDC1050 > - HDC1080 > > Not supported: > - HDC1008 This one is okay now, thanks! Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Signed-off-by: Potin Lai <potin.lai.pt@gmail.com> > --- > drivers/iio/humidity/hdc100x.c | 67 ++++++++++++++++++++++++++++------ > 1 file changed, 56 insertions(+), 11 deletions(-) > > diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c > index 0d514818635cb..31f18cc1cf63c 100644 > --- a/drivers/iio/humidity/hdc100x.c > +++ b/drivers/iio/humidity/hdc100x.c > @@ -34,6 +34,23 @@ > #define HDC100X_REG_CONFIG_ACQ_MODE BIT(12) > #define HDC100X_REG_CONFIG_HEATER_EN BIT(13) > > +#define HDC100X_REG_MFR_ID 0xFE > +#define HDC100X_REG_DEV_ID 0xFF > + > +#define HDC100X_MFR_ID 0x5449 > + > +struct hdc100x_chip_data { > + bool support_mfr_check; > +}; > + > +static const struct hdc100x_chip_data hdc100x_chip_data = { > + .support_mfr_check = true, > +}; > + > +static const struct hdc100x_chip_data hdc1008_chip_data = { > + .support_mfr_check = false, > +}; > + > struct hdc100x_data { > struct i2c_client *client; > struct mutex lock; > @@ -351,8 +368,32 @@ static const struct iio_info hdc100x_info = { > .attrs = &hdc100x_attribute_group, > }; > > +static int hdc100x_read_mfr_id(struct i2c_client *client) > +{ > + return i2c_smbus_read_word_swapped(client, HDC100X_REG_MFR_ID); > +} > + > +static int hdc100x_read_dev_id(struct i2c_client *client) > +{ > + return i2c_smbus_read_word_swapped(client, HDC100X_REG_DEV_ID); > +} > + > +static bool is_valid_hdc100x(struct i2c_client *client) > +{ > + int mfr_id, dev_id; > + > + mfr_id = hdc100x_read_mfr_id(client); > + dev_id = hdc100x_read_dev_id(client); > + if (mfr_id == HDC100X_MFR_ID && > + (dev_id == 0x1000 || dev_id == 0x1050)) > + return true; > + > + return false; > +} > + > static int hdc100x_probe(struct i2c_client *client) > { > + const struct hdc100x_chip_data *chip_data; > struct iio_dev *indio_dev; > struct hdc100x_data *data; > int ret; > @@ -361,6 +402,10 @@ static int hdc100x_probe(struct i2c_client *client) > I2C_FUNC_SMBUS_BYTE | I2C_FUNC_I2C)) > return -EOPNOTSUPP; > > + chip_data = device_get_match_data(&client->dev); > + if (chip_data->support_mfr_check && !is_valid_hdc100x(client)) > + return -EINVAL; > + > indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); > if (!indio_dev) > return -ENOMEM; > @@ -396,22 +441,22 @@ static int hdc100x_probe(struct i2c_client *client) > } > > static const struct i2c_device_id hdc100x_id[] = { > - { "hdc100x", 0 }, > - { "hdc1000", 0 }, > - { "hdc1008", 0 }, > - { "hdc1010", 0 }, > - { "hdc1050", 0 }, > - { "hdc1080", 0 }, > + { "hdc100X", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1000", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1008", (kernel_ulong_t)&hdc1008_chip_data }, > + { "hdc1010", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1050", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1080", (kernel_ulong_t)&hdc100x_chip_data }, > { } > }; > MODULE_DEVICE_TABLE(i2c, hdc100x_id); > > static const struct of_device_id hdc100x_dt_ids[] = { > - { .compatible = "ti,hdc1000" }, > - { .compatible = "ti,hdc1008" }, > - { .compatible = "ti,hdc1010" }, > - { .compatible = "ti,hdc1050" }, > - { .compatible = "ti,hdc1080" }, > + { .compatible = "ti,hdc1000", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1008", .data = &hdc1008_chip_data }, > + { .compatible = "ti,hdc1010", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1050", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1080", .data = &hdc100x_chip_data }, > { } > }; > MODULE_DEVICE_TABLE(of, hdc100x_dt_ids); > -- > 2.31.1 >
On Thu, 28 Jul 2022 12:54:35 +0000 Potin Lai <potin.lai.pt@gmail.com> wrote: > Add manufacturer and device ID checking during probe, and skip the > checking if chip model not supported. > > Supported: > - HDC1000 > - HDC1010 > - HDC1050 > - HDC1080 > > Not supported: > - HDC1008 > > Signed-off-by: Potin Lai <potin.lai.pt@gmail.com> I need some more information on the 'why' of this patch. There are a number of drivers that do a similar ID check but in recent times, that approach has been considered wrong because it breaks potential use of multiple compatible entries in device tree. If a new device comes along and is backwards compatible with an existing one (maybe has new features, but using them is optional) then we want to have an entry that looks like compatible = "ti,hdc1099", "ti,hdc1080" If the new ID is not supported by the kernel that is being used, we still want the driver to 'work' using the fallback compatible. As such, we no generally do the following. 1) If we have a match to a device we know about but it's not the one the firmware tells us to expect, print a warning but operate as if the firmware had been correct - particularly if we know the parts aren't compatible with each other. (this bit is optional as we should be able to assume firmware doesn't do stupid things :) 2) If we don't match at all, print a warning about an unknown device but carry on with assumption that the firmware is correct and this new device ID is backwards compatible with the provided fallback compatible. So if this is just a bit of defensive programming (rather than necessary for some reason not yet explained) then change from returning an error on probe() to printing an warning message but continuing anyway. (which is part (2) of the above) > --- > drivers/iio/humidity/hdc100x.c | 67 ++++++++++++++++++++++++++++------ > 1 file changed, 56 insertions(+), 11 deletions(-) > > diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c > index 0d514818635cb..31f18cc1cf63c 100644 > --- a/drivers/iio/humidity/hdc100x.c > +++ b/drivers/iio/humidity/hdc100x.c > @@ -34,6 +34,23 @@ > #define HDC100X_REG_CONFIG_ACQ_MODE BIT(12) > #define HDC100X_REG_CONFIG_HEATER_EN BIT(13) > > +#define HDC100X_REG_MFR_ID 0xFE > +#define HDC100X_REG_DEV_ID 0xFF > + > +#define HDC100X_MFR_ID 0x5449 > + > +struct hdc100x_chip_data { > + bool support_mfr_check; > +}; > + > +static const struct hdc100x_chip_data hdc100x_chip_data = { > + .support_mfr_check = true, > +}; > + > +static const struct hdc100x_chip_data hdc1008_chip_data = { > + .support_mfr_check = false, > +}; > + > struct hdc100x_data { > struct i2c_client *client; > struct mutex lock; > @@ -351,8 +368,32 @@ static const struct iio_info hdc100x_info = { > .attrs = &hdc100x_attribute_group, > }; > > +static int hdc100x_read_mfr_id(struct i2c_client *client) > +{ > + return i2c_smbus_read_word_swapped(client, HDC100X_REG_MFR_ID); > +} > + > +static int hdc100x_read_dev_id(struct i2c_client *client) > +{ > + return i2c_smbus_read_word_swapped(client, HDC100X_REG_DEV_ID); > +} > + > +static bool is_valid_hdc100x(struct i2c_client *client) > +{ > + int mfr_id, dev_id; > + > + mfr_id = hdc100x_read_mfr_id(client); > + dev_id = hdc100x_read_dev_id(client); > + if (mfr_id == HDC100X_MFR_ID && > + (dev_id == 0x1000 || dev_id == 0x1050)) > + return true; > + > + return false; > +} > + > static int hdc100x_probe(struct i2c_client *client) > { > + const struct hdc100x_chip_data *chip_data; > struct iio_dev *indio_dev; > struct hdc100x_data *data; > int ret; > @@ -361,6 +402,10 @@ static int hdc100x_probe(struct i2c_client *client) > I2C_FUNC_SMBUS_BYTE | I2C_FUNC_I2C)) > return -EOPNOTSUPP; > > + chip_data = device_get_match_data(&client->dev); > + if (chip_data->support_mfr_check && !is_valid_hdc100x(client)) > + return -EINVAL; > + > indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); > if (!indio_dev) > return -ENOMEM; > @@ -396,22 +441,22 @@ static int hdc100x_probe(struct i2c_client *client) > } > > static const struct i2c_device_id hdc100x_id[] = { > - { "hdc100x", 0 }, > - { "hdc1000", 0 }, > - { "hdc1008", 0 }, > - { "hdc1010", 0 }, > - { "hdc1050", 0 }, > - { "hdc1080", 0 }, > + { "hdc100X", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1000", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1008", (kernel_ulong_t)&hdc1008_chip_data }, > + { "hdc1010", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1050", (kernel_ulong_t)&hdc100x_chip_data }, > + { "hdc1080", (kernel_ulong_t)&hdc100x_chip_data }, > { } > }; > MODULE_DEVICE_TABLE(i2c, hdc100x_id); > > static const struct of_device_id hdc100x_dt_ids[] = { > - { .compatible = "ti,hdc1000" }, > - { .compatible = "ti,hdc1008" }, > - { .compatible = "ti,hdc1010" }, > - { .compatible = "ti,hdc1050" }, > - { .compatible = "ti,hdc1080" }, > + { .compatible = "ti,hdc1000", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1008", .data = &hdc1008_chip_data }, > + { .compatible = "ti,hdc1010", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1050", .data = &hdc100x_chip_data }, > + { .compatible = "ti,hdc1080", .data = &hdc100x_chip_data }, > { } > }; > MODULE_DEVICE_TABLE(of, hdc100x_dt_ids);
On 7/31/22 20:09, Jonathan Cameron wrote: > On Thu, 28 Jul 2022 12:54:35 +0000 > Potin Lai <potin.lai.pt@gmail.com> wrote: > >> Add manufacturer and device ID checking during probe, and skip the >> checking if chip model not supported. >> >> Supported: >> - HDC1000 >> - HDC1010 >> - HDC1050 >> - HDC1080 >> >> Not supported: >> - HDC1008 >> >> Signed-off-by: Potin Lai <potin.lai.pt@gmail.com> > I need some more information on the 'why' of this patch. There are a number > of drivers that do a similar ID check but in recent times, that approach has > been considered wrong because it breaks potential use of multiple compatible > entries in device tree. If a new device comes along and is backwards > compatible with an existing one (maybe has new features, but using them is > optional) then we want to have an entry that looks like > > compatible = "ti,hdc1099", "ti,hdc1080" > > If the new ID is not supported by the kernel that is being used, we still > want the driver to 'work' using the fallback compatible. > > As such, we no generally do the following. > > 1) If we have a match to a device we know about but it's not the one the > firmware tells us to expect, print a warning but operate as if the firmware > had been correct - particularly if we know the parts aren't compatible > with each other. (this bit is optional as we should be able to assume firmware > doesn't do stupid things :) > 2) If we don't match at all, print a warning about an unknown device but carry > on with assumption that the firmware is correct and this new device ID is > backwards compatible with the provided fallback compatible. > > So if this is just a bit of defensive programming (rather than necessary for some > reason not yet explained) then change from returning an error on probe() to > printing an warning message but continuing anyway. (which is part (2) of the > above) Hi Jonathan, In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" for 2nd source. This two chip are locate at same bus and same slave address, and we want to use multiple compatibles to support both chips with single device node in device tree. Ex: compatible = "ti,hdc1099", "silabs,si7020"; In order to support this, I need to add ID checking mechanism into the current hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver (because the ID checking is not failed), then success probe with si7020. Base on you explanation, it looks multiple compatibles is not suitable in this case? Would you mind advise us what would be the better approach for our case? Thanks, Potin
On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: > On 7/31/22 20:09, Jonathan Cameron wrote: ... > In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" > for 2nd source. This two chip are locate at same bus and same slave address, > and we want to use multiple compatibles to support both chips with single device > node in device tree. > > Ex: > compatible = "ti,hdc1099", "silabs,si7020"; This is simply broken DT, you must not put incompatible hardware on the same compatible string. DT is by definition the description of a certain platform. What you showed is a combination of incompatible chips in a single DT. > In order to support this, I need to add ID checking mechanism into the current > hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver > (because the ID checking is not failed), then success probe with si7020. > > Base on you explanation, it looks multiple compatibles is not suitable in this > case? Would you mind advise us what would be the better approach for our case? If I may advise... fix your DT by dropping the wrong compatible item.
On Mon, Aug 01, 2022 at 10:22:16AM +0200, Andy Shevchenko wrote: > On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: > > On 7/31/22 20:09, Jonathan Cameron wrote: > > In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" > > for 2nd source. This two chip are locate at same bus and same slave address, > > and we want to use multiple compatibles to support both chips with single device > > node in device tree. > > > > Ex: > > compatible = "ti,hdc1099", "silabs,si7020"; > > This is simply broken DT, you must not put incompatible hardware on > the same compatible string. DT is by definition the description of a > certain platform. What you showed is a combination of incompatible > chips in a single DT. We were mistaken that this is the appropriate way to specify this behavior, partially because it works as long as the probe functions return an error the next matching driver from the compatible will probe. It does seem that specifying two different compatibles like this would violate the intention of the DT spec: The property value consists of a concatenated list of null terminated strings, from most specific to most general. They allow a device to express its compatibility with a family of similar devices, potentially allowing a single device driver to match against several devices. > > > In order to support this, I need to add ID checking mechanism into the current > > hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver > > (because the ID checking is not failed), then success probe with si7020. > > > > Base on you explanation, it looks multiple compatibles is not suitable in this > > case? Would you mind advise us what would be the better approach for our case? > > If I may advise... fix your DT by dropping the wrong compatible item. This doesn't really give any helpful advice. The reality is that these two chips are pin compatible and function compatible but not driver compatible. Boards have been manufactured which are identical except for this chip replaced, due various to chip shortages. Making probe fail so that the next 'compatible' is chosen sounds like it isn't desired. I'm pretty sure you can't have two DT entries for the same i2c address, but with different 'compatible" properties, and even if we did you'd still need probe to fail on one of them. Are there any other suggestions for being able to inform the kernel that one of two chips might be present?
On Mon, Aug 1, 2022 at 6:12 PM Patrick Williams <patrick@stwcx.xyz> wrote: > > On Mon, Aug 01, 2022 at 10:22:16AM +0200, Andy Shevchenko wrote: > > On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: > > > On 7/31/22 20:09, Jonathan Cameron wrote: > > > In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" > > > for 2nd source. This two chip are locate at same bus and same slave address, > > > and we want to use multiple compatibles to support both chips with single device > > > node in device tree. > > > > > > Ex: > > > compatible = "ti,hdc1099", "silabs,si7020"; > > > > This is simply broken DT, you must not put incompatible hardware on > > the same compatible string. DT is by definition the description of a > > certain platform. What you showed is a combination of incompatible > > chips in a single DT. > > We were mistaken that this is the appropriate way to specify this > behavior, partially because it works as long as the probe functions > return an error the next matching driver from the compatible will probe. > It does seem that specifying two different compatibles like this would > violate the intention of the DT spec: > > The property value consists of a concatenated list of null terminated > strings, from most specific to most general. They allow a device to > express its compatibility with a family of similar devices, potentially > allowing a single device driver to match against several devices. > > > > > > In order to support this, I need to add ID checking mechanism into the current > > > hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver > > > (because the ID checking is not failed), then success probe with si7020. > > > > > > Base on you explanation, it looks multiple compatibles is not suitable in this > > > case? Would you mind advise us what would be the better approach for our case? > > > > If I may advise... fix your DT by dropping the wrong compatible item. > > This doesn't really give any helpful advice. Sorry to hear this, but it's the best and correct solution to your problem. Believe me, many Linux people will tell you the same. > The reality is that these two chips are pin compatible and function > compatible but not driver compatible. Boards have been manufactured > which are identical except for this chip replaced, due various to chip > shortages. > > Making probe fail so that the next 'compatible' is chosen sounds like it > isn't desired. I'm pretty sure you can't have two DT entries for the > same i2c address, but with different 'compatible" properties, and even > if we did you'd still need probe to fail on one of them. > > Are there any other suggestions for being able to inform the kernel that > one of two chips might be present? I guess there is a gap in understanding what DT is. DT is the description of the *platform*. Changing any discrete component on the platform is changing the platform.
On Mon, Aug 1, 2022 at 6:26 PM Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Mon, Aug 1, 2022 at 6:12 PM Patrick Williams <patrick@stwcx.xyz> wrote: > > On Mon, Aug 01, 2022 at 10:22:16AM +0200, Andy Shevchenko wrote: > > > On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: > > > > On 7/31/22 20:09, Jonathan Cameron wrote: > > > > In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" > > > > for 2nd source. This two chip are locate at same bus and same slave address, > > > > and we want to use multiple compatibles to support both chips with single device > > > > node in device tree. > > > > > > > > Ex: > > > > compatible = "ti,hdc1099", "silabs,si7020"; > > > > > > This is simply broken DT, you must not put incompatible hardware on > > > the same compatible string. DT is by definition the description of a > > > certain platform. What you showed is a combination of incompatible > > > chips in a single DT. > > > > We were mistaken that this is the appropriate way to specify this > > behavior, partially because it works as long as the probe functions > > return an error the next matching driver from the compatible will probe. > > It does seem that specifying two different compatibles like this would > > violate the intention of the DT spec: > > > > The property value consists of a concatenated list of null terminated > > strings, from most specific to most general. They allow a device to > > express its compatibility with a family of similar devices, potentially > > allowing a single device driver to match against several devices. > > > > > > > > > In order to support this, I need to add ID checking mechanism into the current > > > > hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver > > > > (because the ID checking is not failed), then success probe with si7020. > > > > > > > > Base on you explanation, it looks multiple compatibles is not suitable in this > > > > case? Would you mind advise us what would be the better approach for our case? > > > > > > If I may advise... fix your DT by dropping the wrong compatible item. > > > > This doesn't really give any helpful advice. > > Sorry to hear this, but it's the best and correct solution to your > problem. Believe me, many Linux people will tell you the same. > > > The reality is that these two chips are pin compatible and function > > compatible but not driver compatible. Boards have been manufactured > > which are identical except for this chip replaced, due various to chip > > shortages. > > > > Making probe fail so that the next 'compatible' is chosen sounds like it > > isn't desired. I'm pretty sure you can't have two DT entries for the > > same i2c address, but with different 'compatible" properties, and even > > if we did you'd still need probe to fail on one of them. > > > > Are there any other suggestions for being able to inform the kernel that > > one of two chips might be present? Btw, how would it be solved in ACPI is the playing status bits by firmware, depending on the run-time detected environment (straps, other means). So, you may fix it on bootloader / firmware level by patching DTB with status okay / disabled. I believe in DTB is the number, which can be easily binary patched. > I guess there is a gap in understanding what DT is. DT is the > description of the *platform*. Changing any discrete component on the > platform is changing the platform.
On Mon, 1 Aug 2022 18:30:16 +0200 Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Mon, Aug 1, 2022 at 6:26 PM Andy Shevchenko > <andy.shevchenko@gmail.com> wrote: > > On Mon, Aug 1, 2022 at 6:12 PM Patrick Williams <patrick@stwcx.xyz> wrote: > > > On Mon, Aug 01, 2022 at 10:22:16AM +0200, Andy Shevchenko wrote: > > > > On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: > > > > > On 7/31/22 20:09, Jonathan Cameron wrote: > > > > > In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" > > > > > for 2nd source. This two chip are locate at same bus and same slave address, > > > > > and we want to use multiple compatibles to support both chips with single device > > > > > node in device tree. > > > > > > > > > > Ex: > > > > > compatible = "ti,hdc1099", "silabs,si7020"; > > > > > > > > This is simply broken DT, you must not put incompatible hardware on > > > > the same compatible string. DT is by definition the description of a > > > > certain platform. What you showed is a combination of incompatible > > > > chips in a single DT. > > > > > > We were mistaken that this is the appropriate way to specify this > > > behavior, partially because it works as long as the probe functions > > > return an error the next matching driver from the compatible will probe. > > > It does seem that specifying two different compatibles like this would > > > violate the intention of the DT spec: > > > > > > The property value consists of a concatenated list of null terminated > > > strings, from most specific to most general. They allow a device to > > > express its compatibility with a family of similar devices, potentially > > > allowing a single device driver to match against several devices. > > > > > > > > > > > > In order to support this, I need to add ID checking mechanism into the current > > > > > hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver > > > > > (because the ID checking is not failed), then success probe with si7020. > > > > > > > > > > Base on you explanation, it looks multiple compatibles is not suitable in this > > > > > case? Would you mind advise us what would be the better approach for our case? > > > > > > > > If I may advise... fix your DT by dropping the wrong compatible item. > > > > > > This doesn't really give any helpful advice. > > > > Sorry to hear this, but it's the best and correct solution to your > > problem. Believe me, many Linux people will tell you the same. > > > > > The reality is that these two chips are pin compatible and function > > > compatible but not driver compatible. Boards have been manufactured > > > which are identical except for this chip replaced, due various to chip > > > shortages. > > > > > > Making probe fail so that the next 'compatible' is chosen sounds like it > > > isn't desired. I'm pretty sure you can't have two DT entries for the > > > same i2c address, but with different 'compatible" properties, and even > > > if we did you'd still need probe to fail on one of them. > > > > > > Are there any other suggestions for being able to inform the kernel that > > > one of two chips might be present? > > Btw, how would it be solved in ACPI is the playing status bits by > firmware, depending on the run-time detected environment (straps, > other means). So, you may fix it on bootloader / firmware level by > patching DTB with status okay / disabled. I believe in DTB is the > number, which can be easily binary patched. > Indeed, it's common to have boot firmware prelinux modify the DT. That firmware can do probing if necessary to find out which device is present and by the time Linux loads the DT should be correct for the particular hardware. Often this is done from a high level 'board ID' but nothing stops you doing it this case. I've cc'd the device tree binding maintainers and list, who may be able to give you some useful pointers to examples of people doing this in their boot loaders etc. Thanks, Jonathan > > I guess there is a gap in understanding what DT is. DT is the > > description of the *platform*. Changing any discrete component on the > > platform is changing the platform. > >
On 06/08/2022 20:12, Jonathan Cameron wrote: > On Mon, 1 Aug 2022 18:30:16 +0200 > Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > >> On Mon, Aug 1, 2022 at 6:26 PM Andy Shevchenko >> <andy.shevchenko@gmail.com> wrote: >>> On Mon, Aug 1, 2022 at 6:12 PM Patrick Williams <patrick@stwcx.xyz> wrote: >>>> On Mon, Aug 01, 2022 at 10:22:16AM +0200, Andy Shevchenko wrote: >>>>> On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@gmail.com> wrote: >>>>>> On 7/31/22 20:09, Jonathan Cameron wrote: >>>>>> In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020" >>>>>> for 2nd source. This two chip are locate at same bus and same slave address, >>>>>> and we want to use multiple compatibles to support both chips with single device >>>>>> node in device tree. >>>>>> >>>>>> Ex: >>>>>> compatible = "ti,hdc1099", "silabs,si7020"; >>>>> >>>>> This is simply broken DT, you must not put incompatible hardware on >>>>> the same compatible string. DT is by definition the description of a >>>>> certain platform. What you showed is a combination of incompatible >>>>> chips in a single DT. >>>> >>>> We were mistaken that this is the appropriate way to specify this >>>> behavior, partially because it works as long as the probe functions >>>> return an error the next matching driver from the compatible will probe. >>>> It does seem that specifying two different compatibles like this would >>>> violate the intention of the DT spec: >>>> >>>> The property value consists of a concatenated list of null terminated >>>> strings, from most specific to most general. They allow a device to >>>> express its compatibility with a family of similar devices, potentially >>>> allowing a single device driver to match against several devices. >>>> >>>>> >>>>>> In order to support this, I need to add ID checking mechanism into the current >>>>>> hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver >>>>>> (because the ID checking is not failed), then success probe with si7020. >>>>>> >>>>>> Base on you explanation, it looks multiple compatibles is not suitable in this >>>>>> case? Would you mind advise us what would be the better approach for our case? >>>>> >>>>> If I may advise... fix your DT by dropping the wrong compatible item. >>>> >>>> This doesn't really give any helpful advice. >>> >>> Sorry to hear this, but it's the best and correct solution to your >>> problem. Believe me, many Linux people will tell you the same. >>> >>>> The reality is that these two chips are pin compatible and function >>>> compatible but not driver compatible. There is no such thing as driver compatible, in the terms of Devicetree. Implementation does not matter. The compatibles and binding should reflect the hardware (and its programming model). > Boards have been manufactured >>>> which are identical except for this chip replaced, due various to chip >>>> shortages. The question is - whether the programming model (e.g. all I2C registers) are similar or exactly the same? >>>> >>>> Making probe fail so that the next 'compatible' is chosen sounds like it >>>> isn't desired. Yes, it is not desired because any probe failure is indication of test failures in automated systems, so you do not develop a system which in normal conditions has a failure. I don't understand why you cannot include in this driver support for second device? Or if second device is so different, why you want to support different hardware with the same device node. This contradicts the very basic of Devicetree - description of hardware. Best regards, Krzysztof
On Mon, Aug 8, 2022 at 11:40 AM Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote: > On 06/08/2022 20:12, Jonathan Cameron wrote: ... > >>>>>> compatible = "ti,hdc1099", "silabs,si7020"; ... > Or if second device is so different, why you want to support different > hardware with the same device node. This contradicts the very basic of > Devicetree - description of hardware. Briefly looking into the above mentioned drivers points to the above case, broken DT principles ==> broken DT ==> nothing to fix in the Linux kernel.
diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c index 0d514818635cb..31f18cc1cf63c 100644 --- a/drivers/iio/humidity/hdc100x.c +++ b/drivers/iio/humidity/hdc100x.c @@ -34,6 +34,23 @@ #define HDC100X_REG_CONFIG_ACQ_MODE BIT(12) #define HDC100X_REG_CONFIG_HEATER_EN BIT(13) +#define HDC100X_REG_MFR_ID 0xFE +#define HDC100X_REG_DEV_ID 0xFF + +#define HDC100X_MFR_ID 0x5449 + +struct hdc100x_chip_data { + bool support_mfr_check; +}; + +static const struct hdc100x_chip_data hdc100x_chip_data = { + .support_mfr_check = true, +}; + +static const struct hdc100x_chip_data hdc1008_chip_data = { + .support_mfr_check = false, +}; + struct hdc100x_data { struct i2c_client *client; struct mutex lock; @@ -351,8 +368,32 @@ static const struct iio_info hdc100x_info = { .attrs = &hdc100x_attribute_group, }; +static int hdc100x_read_mfr_id(struct i2c_client *client) +{ + return i2c_smbus_read_word_swapped(client, HDC100X_REG_MFR_ID); +} + +static int hdc100x_read_dev_id(struct i2c_client *client) +{ + return i2c_smbus_read_word_swapped(client, HDC100X_REG_DEV_ID); +} + +static bool is_valid_hdc100x(struct i2c_client *client) +{ + int mfr_id, dev_id; + + mfr_id = hdc100x_read_mfr_id(client); + dev_id = hdc100x_read_dev_id(client); + if (mfr_id == HDC100X_MFR_ID && + (dev_id == 0x1000 || dev_id == 0x1050)) + return true; + + return false; +} + static int hdc100x_probe(struct i2c_client *client) { + const struct hdc100x_chip_data *chip_data; struct iio_dev *indio_dev; struct hdc100x_data *data; int ret; @@ -361,6 +402,10 @@ static int hdc100x_probe(struct i2c_client *client) I2C_FUNC_SMBUS_BYTE | I2C_FUNC_I2C)) return -EOPNOTSUPP; + chip_data = device_get_match_data(&client->dev); + if (chip_data->support_mfr_check && !is_valid_hdc100x(client)) + return -EINVAL; + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); if (!indio_dev) return -ENOMEM; @@ -396,22 +441,22 @@ static int hdc100x_probe(struct i2c_client *client) } static const struct i2c_device_id hdc100x_id[] = { - { "hdc100x", 0 }, - { "hdc1000", 0 }, - { "hdc1008", 0 }, - { "hdc1010", 0 }, - { "hdc1050", 0 }, - { "hdc1080", 0 }, + { "hdc100X", (kernel_ulong_t)&hdc100x_chip_data }, + { "hdc1000", (kernel_ulong_t)&hdc100x_chip_data }, + { "hdc1008", (kernel_ulong_t)&hdc1008_chip_data }, + { "hdc1010", (kernel_ulong_t)&hdc100x_chip_data }, + { "hdc1050", (kernel_ulong_t)&hdc100x_chip_data }, + { "hdc1080", (kernel_ulong_t)&hdc100x_chip_data }, { } }; MODULE_DEVICE_TABLE(i2c, hdc100x_id); static const struct of_device_id hdc100x_dt_ids[] = { - { .compatible = "ti,hdc1000" }, - { .compatible = "ti,hdc1008" }, - { .compatible = "ti,hdc1010" }, - { .compatible = "ti,hdc1050" }, - { .compatible = "ti,hdc1080" }, + { .compatible = "ti,hdc1000", .data = &hdc100x_chip_data }, + { .compatible = "ti,hdc1008", .data = &hdc1008_chip_data }, + { .compatible = "ti,hdc1010", .data = &hdc100x_chip_data }, + { .compatible = "ti,hdc1050", .data = &hdc100x_chip_data }, + { .compatible = "ti,hdc1080", .data = &hdc100x_chip_data }, { } }; MODULE_DEVICE_TABLE(of, hdc100x_dt_ids);
Add manufacturer and device ID checking during probe, and skip the checking if chip model not supported. Supported: - HDC1000 - HDC1010 - HDC1050 - HDC1080 Not supported: - HDC1008 Signed-off-by: Potin Lai <potin.lai.pt@gmail.com> --- drivers/iio/humidity/hdc100x.c | 67 ++++++++++++++++++++++++++++------ 1 file changed, 56 insertions(+), 11 deletions(-)