Re: [PATCH v3] dt-bindings: iio: dac: Change the I2C slave address for ds4422/4424 to its correct value

Re: [PATCH v3] dt-bindings: iio: dac: Change the I2C slave address for ds4422/4424 to its correct value

[Krzysztof Kozlowski]

On 24/10/2022 13:50, Rajat Khandelwal wrote:
> The datasheet states that the slave address for the device is 0x20
> when the pins A0 and A1 are ground. The DT binding has been using
> 0x10 as the value and I think it should be 0x20 as per datasheet.
> 
> Signed-off-by: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
> ---


Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

[PATCH v3] dt-bindings: iio: dac: Change the I2C slave address for ds4422/4424 to its correct value

[Rajat Khandelwal]

The datasheet states that the slave address for the device is 0x20
when the pins A0 and A1 are ground. The DT binding has been using
0x10 as the value and I think it should be 0x20 as per datasheet.

Signed-off-by: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
---

v3:
1. Subject prefix added
2. Improvised 'examples:'

 Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
index 264fa7c5fe3a..e7c7c103d1dd 100644
--- a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
+++ b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
@@ -36,9 +36,9 @@ examples:
         #address-cells = <1>;
         #size-cells = <0>;
 
-        dac@10 {
+        dac@20 {
             compatible = "maxim,ds4424";
-            reg = <0x10>; /* When A0, A1 pins are ground */
+            reg = <0x20>; /* When A0, A1 pins are ground */
             vcc-supply = <&vcc_3v3>;
         };
     };
-- 
2.34.1

Re: [PATCH v3] dt-bindings: iio: dac: Change the I2C slave address for ds4422/4424 to its correct value

[Jonathan Cameron]

On Sun, 23 Oct 2022 19:23:09 -0400
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> On 24/10/2022 13:50, Rajat Khandelwal wrote:
> > The datasheet states that the slave address for the device is 0x20
> > when the pins A0 and A1 are ground. The DT binding has been using
> > 0x10 as the value and I think it should be 0x20 as per datasheet.
> > 
> > Signed-off-by: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
> > ---  
> 
> 
> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> 

hmm. This is curious. So the datasheet indeed provides a table saying
grounding both pins sets the address to 0x20, however take a look at
Figure 2 which says the address is
A1 | A0 | 1 | 0 | 0 | 0 | 0

or 0x10 as per the example.  My guess is someone forgot that i2c addresses
are 7 bits and the lowest bit of the first byte is used for R/W control.

So unless we have this verified on hardware (implying that the address table
is correct in this sense) I'm not keen to take this.
I doubt that is the case given it has 8 bit addresses (0xe0) and i2c addresses
are 7 bits.

Jonathan


> Best regards,
> Krzysztof
>