Re: [PATCH v2 00/14] Add Microchip ZL3073x support (part 1)

Michal Schmidt
2025-04-11T14:27:22Z

On Fri, Apr 11, 2025 at 9:26 AM Lee Jones <lee@kernel.org> wrote:
> On Wed, 09 Apr 2025, Ivan Vecera wrote:
> > Add support for Microchip Azurite DPLL/PTP/SyncE chip family that
> > provides DPLL and PTP functionality. This series bring first part
> > that adds the common MFD driver that provides an access to the bus
> > that can be either I2C or SPI.
> > [...]
>
> Not only are all of the added abstractions and ugly MACROs hard to read
> and troublesome to maintain, they're also completely unnecessary at this
> (driver) level. Nicely authored, easy to read / maintain code wins over
> clever code 95% of the time.

Hello Lee,

IMHO defining the registers with the ZL3073X_REG*_DEF macros is both
clever and easy to read / maintain. On one line I can see the register
name, size and address. For the indexed registers also their count and
the stride. It's almost like looking at a datasheet. And the
type-checking for accessing the registers using the correct size is
nice. I even liked the paranoid WARN_ON for checking the index
overflows.

The weak point is the non-obvious usage in call sites. Seeing:
rc = zl3073x_read_id(zldev, &id);
can be confusing. One will not find the function with cscope or grep.
Nothing immediately suggests that there's macro magic behind it.
What if usage had to be just slightly more explicit?:
rc = ZL3073X_READ(id, zldev, &id);

I could immediately see that ZL3073X_READ is a macro. Its definition
would be near the definitions of the ZL3073X_REG*_DEF macros, so I
could correctly guess these things are related.
The 1st argument of the ZL3073X_READ macro is the register name.
(There would be a ZL3073X_READ_IDX with one more argument for indexed
registers.)
In vim, having the cursor on the 1st argument (id) and pressing gD
takes me to the corresponding ZL3073X_REG16_DEF line.

Would it still be too ugly in your view?

Michal