linux-kernel - Re: [PATCH v3 2/4] dt-bindings: can: fixed-transceiver: Add new CAN fixed transceiver bindings

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Date:   Wed, 9 Aug 2017 20:00:11 -0500
From:   Franklin S Cooper Jr <fcooper@...com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-can@...r.kernel.org>,
        <wg@...ndegger.com>, <mkl@...gutronix.de>, <robh+dt@...nel.org>,
        <quentin.schulz@...e-electrons.com>,
        <dev.kurt@...dijck-laurijssen.be>, <andrew@...n.ch>,
        <socketcan@...tkopp.net>
Subject: Re: [PATCH v3 2/4] dt-bindings: can: fixed-transceiver: Add new CAN
 fixed transceiver bindings

Hi Sergei,

On 08/03/2017 10:38 AM, Franklin S Cooper Jr wrote:
> 
> 
> On 08/03/2017 07:22 AM, Sergei Shtylyov wrote:
>> On 08/03/2017 12:48 PM, Franklin S Cooper Jr wrote:
>>
>>>>> Add documentation to describe usage of the new fixed transceiver
>>>>> binding.
>>>>> This new binding is applicable for any CAN device therefore it
>>>>> exists as
>>>>> its own document.
>>>>>
>>>>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
>>>>> ---
>>>>>    .../bindings/net/can/fixed-transceiver.txt         | 24
>>>>> ++++++++++++++++++++++
>>>>>    1 file changed, 24 insertions(+)
>>>>>    create mode 100644
>>>>> Documentation/devicetree/bindings/net/can/fixed-transceiver.txt
>>>>>
>>>>> diff --git
>>>>> a/Documentation/devicetree/bindings/net/can/fixed-transceiver.txt
>>>>> b/Documentation/devicetree/bindings/net/can/fixed-transceiver.txt
>>>>> new file mode 100644
>>>>> index 0000000..2f58838b
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/net/can/fixed-transceiver.txt
>>>>> @@ -0,0 +1,24 @@
>>>>> +Fixed transceiver Device Tree binding
>>>>> +------------------------------
>>>>> +
>>>>> +CAN transceiver typically limits the max speed in standard CAN and
>>>>> CAN FD
>>>>> +modes. Typically these limitations are static and the transceivers
>>>>> themselves
>>>>> +provide no way to detect this limitation at runtime. For this
>>>>> situation,
>>>>> +the "fixed-transceiver" node can be used.
>>>>> +
>>>>> +Required Properties:
>>>>> + max-bitrate:    a positive non 0 value that determines the max
>>>>> +        speed that CAN/CAN-FD can run. Any other value
>>>>> +        will be ignored.
>>>>> +
>>>>> +Examples:
>>>>> +
>>>>> +Based on Texas Instrument's TCAN1042HGV CAN Transceiver
>>>>> +
>>>>> +m_can0 {
>>>>> +    ....
>>>>> +    fixed-transceiver@0 {
>>>>
>>>>     The <unit-address> (after @) must only be specified if there's "reg"
>>>
>>> Sorry. Fixed this in my v2 and some how it came back. Will fix.
>>>
>>>> prop in the device node. Also, please name the node "can-transceiver@"
>>>> to be more in line with the DT spec. which requires generic node names.
>>>
>>> Its possible for future can transceivers drivers to be created. So I
>>
>>    So what? Ah, you are using the node name to match in the CAN drivers...
>>
>>> thought including fixed was important to indicate that this is a "dumb"
>>> transceiver similar to "fixed-link".
>>
>>    I'm not sure the "fixed-link" MAC subnode assumed any transceiver at
>> all...
> 
> Your right. I wasn't trying to imply that it does. What I meant was that
> having a node named "can-transceiver" may be a bit confusing in the
> future if can transceiver drivers are created. Prefix of "fixed" atleast
> to me makes it clear that this is something unique or a generic
> transceiver with limitations. Similar to "fixed-link" which is for MACs
> not connected to MDIO managed phy. Calling this subnode
> "can-transceiver" to me would be like renaming "fixed-link" to "phy".
> 
>>
>>> So would "fixed-can-transceiver" be
>>> ok or do you want to go with can-transceiver?
>>
>>    I'm somewhat perplexed at this point...
> 
> If my reasoning still didn't change your views then I'll make the switch.

I went ahead and made your suggested switch in my v4. Thanks for taking
the time to review this series.
>>
>> MBR, Sergei