On Wed, 10 Jun 2020, Michael Walle wrote:
> Am 2020-06-09 21:45, schrieb Lee Jones:
> > On Tue, 09 Jun 2020, Michael Walle wrote:
> > > > We do not need a 'simple-regmap' solution for your use-case.
> > > >
> > > > Since your device's registers are segregated, just split up the
> > > > register map and allocate each sub-device with it's own slice.
> > >
> > > I don't get it, could you make a device tree example for my
> > > use-case? (see also above)
> >
> > &i2cbus {
> > mfd-device@10 {
> > compatible = "simple-mfd";
> > reg = <10>;
> >
> > sub-device@10 {
> > compatible = "vendor,sub-device";
> > reg = <10>;
> > };
> > };
> >
> > The Regmap config would be present in each of the child devices.
> >
> > Each child device would call devm_regmap_init_i2c() in .probe().
>
> Ah, I see. If I'm not wrong, this still means to create an i2c
> device driver with the name "simple-mfd".
Yes, it does.
> Besides that, I don't like this, because:
> - Rob already expressed its concerns with "simple-mfd" and so on.
Where did this take place? I'd like to read up on this.
> - you need to duplicate the config in each sub device
You can have a share a single config.
> - which also means you are restricting the sub devices to be
> i2c only (unless you implement and duplicate other regmap configs,
> too). For this driver, SPI and MMIO may be viable options.
You could also have a shared implementation to choose between different
busses.
> Thus, I'd rather implement a simple-mfd.c which implement a common
> I2C driver for now and populate its children using
> devm_of_platform_populate(). This could be extended to support other
> type of regmaps like SPI in the future.
>
> Also some MFD drivers could be moved to this, a likely candidate is
> the smsc-ece1099.c. Although I don't really understand its purpose,
> if don't have CONFIG_OF.
>
> Judging from the existing code, this simple-mfd.c wouldn't just be
> "a list of compatible" strings but also additional quirks and tweaks
> for particular devices in this list.
Hold off on the simple-mfd.c idea, as I'm not taken by it yet and
wouldn't want you to waste your time. I have another idea which would
help. Give me a few days to put something together.
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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