trivial-devices with vdd-supply: true

trivial-devices with vdd-supply: true

[Javier Carrasco]

Hi,

I am trying to figure out the current policy to add trivial devices
(I2C/SPI devices with at most one interrupt) to trivial-devices.yaml or
include a dedicated file.

Apparently, bindings for the same sort of devices where "vdd-supply" is
provided require their own file, and I wonder why there is no
"vdd/supplied/whatever-trivial-devices.yaml".

Instead, files with trivial bindings + "vdd-supply: true" are added on a
regular basis. That property is not saying anything specific about the
device beyond that it needs a supply, which is very common. Is that
intended and no more generic bindings are desired?

On the other hand, trivial-devices.yaml includes several devices that do
require a single supply (e.g. several sensors), but it is not explicitly
documented. Did the requirement of providing vdd-supply arise after
those devices were added to trivial-devices? I think that some devices
that were added to trivial-devices in the last months could have also
had a vdd-supply property, so I am not sure about the rules to choose
one way or another.

Thanks and best regards,
Javier Carrasco

Re: trivial-devices with vdd-supply: true

[Krzysztof Kozlowski]

On 09/03/2024 13:22, Javier Carrasco wrote:
> Hi,
> 
> I am trying to figure out the current policy to add trivial devices
> (I2C/SPI devices with at most one interrupt) to trivial-devices.yaml or
> include a dedicated file.
> 
> Apparently, bindings for the same sort of devices where "vdd-supply" is
> provided require their own file, and I wonder why there is no
> "vdd/supplied/whatever-trivial-devices.yaml".
> 
> Instead, files with trivial bindings + "vdd-supply: true" are added on a
> regular basis. That property is not saying anything specific about the

Anything needing supply is not really trivial anymore, because we want
the supply name to match more or less what's in datasheet.

Solution is sometimes to allow generic "power-supply", like panels have,
AFAIR. If you have new device, just add new binding for it or add the
device to existing binding with very, very similar device.

See also:
https://lore.kernel.org/all/YUz+psAILnF5L5GH@robh.at.kernel.org/
https://lore.kernel.org/all/20210921131804.GC1864238@roeck-us.net/
https://lore.kernel.org/all/CAL_JsqKJgvK8g+zbzLCBxnKbgAioBcdHWNAvqe4Z9BzkNMwPpA@mail.gmail.com/


> device beyond that it needs a supply, which is very common. Is that
> intended and no more generic bindings are desired?
> 
> On the other hand, trivial-devices.yaml includes several devices that do
> require a single supply (e.g. several sensors), but it is not explicitly
> documented. Did the requirement of providing vdd-supply arise after
> those devices were added to trivial-devices? I think that some devices

You would need to analyze the history... requirement of providing
supplies was kind of always. Just like trivial devices were.

> that were added to trivial-devices in the last months could have also
> had a vdd-supply property, so I am not sure about the rules to choose
> one way or another.

https://lore.kernel.org/all/20230505204810.GB3506915-robh@kernel.org/

Best regards,
Krzysztof

Re: trivial-devices with vdd-supply: true

[Javier Carrasco]

On 09.03.24 16:00, Krzysztof Kozlowski wrote:
> On 09/03/2024 13:22, Javier Carrasco wrote:
>> Hi,
>>
>> I am trying to figure out the current policy to add trivial devices
>> (I2C/SPI devices with at most one interrupt) to trivial-devices.yaml or
>> include a dedicated file.
>>
>> Apparently, bindings for the same sort of devices where "vdd-supply" is
>> provided require their own file, and I wonder why there is no
>> "vdd/supplied/whatever-trivial-devices.yaml".
>>
>> Instead, files with trivial bindings + "vdd-supply: true" are added on a
>> regular basis. That property is not saying anything specific about the
> 
> Anything needing supply is not really trivial anymore, because we want
> the supply name to match more or less what's in datasheet.
> 

That seems to be the case for devices with multiple supplies, but for a
single supply "vdd" seems to be preferred over any name in the datasheet
like "vcc", probably due to a copy+paste effect?

> Solution is sometimes to allow generic "power-supply", like panels have,
> AFAIR. If you have new device, just add new binding for it or add the
> device to existing binding with very, very similar device.
> 
> See also:
> https://lore.kernel.org/all/YUz+psAILnF5L5GH@robh.at.kernel.org/
> https://lore.kernel.org/all/20210921131804.GC1864238@roeck-us.net/
> https://lore.kernel.org/all/CAL_JsqKJgvK8g+zbzLCBxnKbgAioBcdHWNAvqe4Z9BzkNMwPpA@mail.gmail.com/
> 
> 
>> device beyond that it needs a supply, which is very common. Is that
>> intended and no more generic bindings are desired?
>>
>> On the other hand, trivial-devices.yaml includes several devices that do
>> require a single supply (e.g. several sensors), but it is not explicitly
>> documented. Did the requirement of providing vdd-supply arise after
>> those devices were added to trivial-devices? I think that some devices
> 
> You would need to analyze the history... requirement of providing
> supplies was kind of always. Just like trivial devices were.
> 
>> that were added to trivial-devices in the last months could have also
>> had a vdd-supply property, so I am not sure about the rules to choose
>> one way or another.
> 
> https://lore.kernel.org/all/20230505204810.GB3506915-robh@kernel.org/
> 
> Best regards,
> Krzysztof
> 

Thank you for the references. In that case a device in
trivial-devices.yaml is better than no bindings at all, but if a supply
is required (which is often the case), dedicated bindings or addition to
existing bindings from a very, very similar device is better.

Best regards,
Javier Carrasco