Re: [PATCH v3 1/8] dt-bindings: misc: Add mikrobus-connector

["Russell King (Oracle)" <linux@xxxxxxxxxxxxxxx>]

On Fri, Mar 15, 2024 at 09:09:11PM +0100, Krzysztof Kozlowski wrote:
> > +properties:
> > +  compatible:
> > +    const: mikrobus-connector
> 
> Hm, why do you create binding for the connector, not for some sort of
> controller? Please provide some rationale for this in commit msg.

I think you have a distorted view. I refer you to the Mikroe mikroBUS
specification - it's _just_ a connector which provides a fairly
standardised purpose for each pin and the electrical specifications.
For example of the pins: power, UART, SPIs, I2C, PWM, and analogue
pins.

> > +  pinctrl-names:
> > +    items:
> > +      - const: default
> > +      - const: pwm_default
> > +      - const: pwm_gpio
> > +      - const: uart_default
> > +      - const: uart_gpio
> > +      - const: i2c_default
> > +      - const: i2c_gpio
> > +      - const: spi_default
> > +      - const: spi_gpio
> 
> I fail to see why such choice is related to the connector itself.

This isn't a choice at all. Here's the list of pins:

Analog - AN
Reset - RST
SPI Chip Select - CS
SPI Clock - SCK
SPI Master Input Slave Output - MISO
SPI Master Output Slave Input - MOSI
VCC-3.3V power - +3.3V
Reference Ground - GND
PWM - PWM output
INT - Hardware Interrupt
RX - UART Receive
TX - UART Transmit
SCL - I2C Clock
SDA - I2C Data
+5V - VCC-5V power
GND - Reference Ground

Any data pin can be a GPIO if e.g. a relay board is plugged in, even
if some of the other pins are used for e.g. UART purposes. For example,
a GPS board that provides the GPS data over the UART pins, and the
PPS signal through a different pin.

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