| Message ID | 20200910134239.192030-1-jonathanh@nvidia.com |
|---|---|
| Headers | show |
| Series | Add support for custom names for AT24 EEPROMs | expand |
On Thu, Sep 10, 2020 at 3:43 PM Jon Hunter <jonathanh@nvidia.com> wrote: > > The AT24 EEPROM driver does not initialise the 'id' field of the > nvmem_config structure and because the entire structure is not > initialised, it ends up with a random value. This causes the NVMEM > driver to append the device 'devid' value to name of the NVMEM > device. Although this is not a problem per-se, for I2C devices such as > the AT24, that already have a device unique name, there does not seem > much value in appending an additional 0 to the I2C name. For example, > appending a 0 to an I2C device name such as 1-0050 does not seem > necessary and maybe even a bit confusing. Therefore, fix this by > setting the NVMEM config.id to NVMEM_DEVID_NONE for AT24 EEPROMs. > > Signed-off-by: Jon Hunter <jonathanh@nvidia.com> > --- > drivers/misc/eeprom/at24.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > index e9df1ca251df..3f7a3bb6a36c 100644 > --- a/drivers/misc/eeprom/at24.c > +++ b/drivers/misc/eeprom/at24.c > @@ -715,6 +715,7 @@ static int at24_probe(struct i2c_client *client) > > nvmem_config.name = dev_name(dev); > nvmem_config.dev = dev; > + nvmem_config.id = NVMEM_DEVID_NONE; > nvmem_config.read_only = !writable; > nvmem_config.root_only = !(flags & AT24_FLAG_IRUGO); > nvmem_config.owner = THIS_MODULE; > -- > 2.25.1 > This patch is correct and thanks for catching it. I vaguely recall wondering at some point why the appended 0 in the nvmem name for at24. Unfortunately this change would affect how the device is visible in user-space in /sys/bus/nvmem/devices/ and this could break existing users. Also: there are many in-kernel users that would need to be updated. I'm afraid we'll need some sort of backward compatibility. Bartosz
On 10/09/2020 16:35, Bartosz Golaszewski wrote: > On Thu, Sep 10, 2020 at 3:43 PM Jon Hunter <jonathanh@nvidia.com> wrote: >> >> The AT24 EEPROM driver does not initialise the 'id' field of the >> nvmem_config structure and because the entire structure is not >> initialised, it ends up with a random value. This causes the NVMEM >> driver to append the device 'devid' value to name of the NVMEM >> device. Although this is not a problem per-se, for I2C devices such as >> the AT24, that already have a device unique name, there does not seem >> much value in appending an additional 0 to the I2C name. For example, >> appending a 0 to an I2C device name such as 1-0050 does not seem >> necessary and maybe even a bit confusing. Therefore, fix this by >> setting the NVMEM config.id to NVMEM_DEVID_NONE for AT24 EEPROMs. >> >> Signed-off-by: Jon Hunter <jonathanh@nvidia.com> >> --- >> drivers/misc/eeprom/at24.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c >> index e9df1ca251df..3f7a3bb6a36c 100644 >> --- a/drivers/misc/eeprom/at24.c >> +++ b/drivers/misc/eeprom/at24.c >> @@ -715,6 +715,7 @@ static int at24_probe(struct i2c_client *client) >> >> nvmem_config.name = dev_name(dev); >> nvmem_config.dev = dev; >> + nvmem_config.id = NVMEM_DEVID_NONE; >> nvmem_config.read_only = !writable; >> nvmem_config.root_only = !(flags & AT24_FLAG_IRUGO); >> nvmem_config.owner = THIS_MODULE; >> -- >> 2.25.1 >> > > This patch is correct and thanks for catching it. I vaguely recall > wondering at some point why the appended 0 in the nvmem name for at24. > Unfortunately this change would affect how the device is visible in > user-space in /sys/bus/nvmem/devices/ and this could break existing > users. Also: there are many in-kernel users that would need to be > updated. I'm afraid we'll need some sort of backward compatibility. Thanks, yes that is a problem. I guess for now we could explicitly init to NVMEM_DEVID_AUTO or maybe just 0 so that it defaults to the same path in the NVMEM driver. However, I am not sure how we can make allow some devices to use NVMEM_DEVID_NONE and others use something else. This is not really something that we can describe in DT because it has nothing to do with h/w. Cheers Jon
On 10/09/2020 19:15, Jon Hunter wrote: > > On 10/09/2020 16:35, Bartosz Golaszewski wrote: >> On Thu, Sep 10, 2020 at 3:43 PM Jon Hunter <jonathanh@nvidia.com> wrote: >>> >>> The AT24 EEPROM driver does not initialise the 'id' field of the >>> nvmem_config structure and because the entire structure is not >>> initialised, it ends up with a random value. This causes the NVMEM >>> driver to append the device 'devid' value to name of the NVMEM >>> device. Although this is not a problem per-se, for I2C devices such as >>> the AT24, that already have a device unique name, there does not seem >>> much value in appending an additional 0 to the I2C name. For example, >>> appending a 0 to an I2C device name such as 1-0050 does not seem >>> necessary and maybe even a bit confusing. Therefore, fix this by >>> setting the NVMEM config.id to NVMEM_DEVID_NONE for AT24 EEPROMs. >>> >>> Signed-off-by: Jon Hunter <jonathanh@nvidia.com> >>> --- >>> drivers/misc/eeprom/at24.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c >>> index e9df1ca251df..3f7a3bb6a36c 100644 >>> --- a/drivers/misc/eeprom/at24.c >>> +++ b/drivers/misc/eeprom/at24.c >>> @@ -715,6 +715,7 @@ static int at24_probe(struct i2c_client *client) >>> >>> nvmem_config.name = dev_name(dev); >>> nvmem_config.dev = dev; >>> + nvmem_config.id = NVMEM_DEVID_NONE; >>> nvmem_config.read_only = !writable; >>> nvmem_config.root_only = !(flags & AT24_FLAG_IRUGO); >>> nvmem_config.owner = THIS_MODULE; >>> -- >>> 2.25.1 >>> >> >> This patch is correct and thanks for catching it. I vaguely recall >> wondering at some point why the appended 0 in the nvmem name for at24. >> Unfortunately this change would affect how the device is visible in >> user-space in /sys/bus/nvmem/devices/ and this could break existing >> users. Also: there are many in-kernel users that would need to be >> updated. I'm afraid we'll need some sort of backward compatibility. > > > Thanks, yes that is a problem. I guess for now we could explicitly init > to NVMEM_DEVID_AUTO or maybe just 0 so that it defaults to the same path > in the NVMEM driver. However, I am not sure how we can make allow some > devices to use NVMEM_DEVID_NONE and others use something else. This is > not really something that we can describe in DT because it has nothing > to do with h/w. Unless we make the configuration of the 'id' dependent on the 'label' property so something like ... if (device_property_present(dev, "label")) { nvmem_config.id = NVMEM_DEVID_NONE; err = device_property_read_string(dev, "label", &nvmem_config.name); if (err) return err; } else { nvmem_config.id = NVMEM_DEVID_AUTO; nvmem_config.name = dev_name(dev); } Cheers Jon
On Thu, Sep 10, 2020 at 8:19 PM Jon Hunter <jonathanh@nvidia.com> wrote: > > > On 10/09/2020 19:15, Jon Hunter wrote: > > > > On 10/09/2020 16:35, Bartosz Golaszewski wrote: > >> On Thu, Sep 10, 2020 at 3:43 PM Jon Hunter <jonathanh@nvidia.com> wrote: > >>> > >>> The AT24 EEPROM driver does not initialise the 'id' field of the > >>> nvmem_config structure and because the entire structure is not > >>> initialised, it ends up with a random value. This causes the NVMEM > >>> driver to append the device 'devid' value to name of the NVMEM > >>> device. Although this is not a problem per-se, for I2C devices such as > >>> the AT24, that already have a device unique name, there does not seem > >>> much value in appending an additional 0 to the I2C name. For example, > >>> appending a 0 to an I2C device name such as 1-0050 does not seem > >>> necessary and maybe even a bit confusing. Therefore, fix this by > >>> setting the NVMEM config.id to NVMEM_DEVID_NONE for AT24 EEPROMs. > >>> > >>> Signed-off-by: Jon Hunter <jonathanh@nvidia.com> > >>> --- > >>> drivers/misc/eeprom/at24.c | 1 + > >>> 1 file changed, 1 insertion(+) > >>> > >>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > >>> index e9df1ca251df..3f7a3bb6a36c 100644 > >>> --- a/drivers/misc/eeprom/at24.c > >>> +++ b/drivers/misc/eeprom/at24.c > >>> @@ -715,6 +715,7 @@ static int at24_probe(struct i2c_client *client) > >>> > >>> nvmem_config.name = dev_name(dev); > >>> nvmem_config.dev = dev; > >>> + nvmem_config.id = NVMEM_DEVID_NONE; > >>> nvmem_config.read_only = !writable; > >>> nvmem_config.root_only = !(flags & AT24_FLAG_IRUGO); > >>> nvmem_config.owner = THIS_MODULE; > >>> -- > >>> 2.25.1 > >>> > >> > >> This patch is correct and thanks for catching it. I vaguely recall > >> wondering at some point why the appended 0 in the nvmem name for at24. > >> Unfortunately this change would affect how the device is visible in > >> user-space in /sys/bus/nvmem/devices/ and this could break existing > >> users. Also: there are many in-kernel users that would need to be > >> updated. I'm afraid we'll need some sort of backward compatibility. > > > > > > Thanks, yes that is a problem. I guess for now we could explicitly init > > to NVMEM_DEVID_AUTO or maybe just 0 so that it defaults to the same path > > in the NVMEM driver. However, I am not sure how we can make allow some > > devices to use NVMEM_DEVID_NONE and others use something else. This is > > not really something that we can describe in DT because it has nothing > > to do with h/w. > > > Unless we make the configuration of the 'id' dependent on the 'label' > property so something like ... > > if (device_property_present(dev, "label")) { > nvmem_config.id = NVMEM_DEVID_NONE; > err = device_property_read_string(dev, "label", > &nvmem_config.name); > if (err) > return err; > } else { > nvmem_config.id = NVMEM_DEVID_AUTO; > nvmem_config.name = dev_name(dev); > } > > Cheers > Jon > > -- > nvpublic Yes, this looks like the best compromise we can get for now. Please make sure to document why we do this in the code. Bartosz