[RFC 0/9] Regmap over USB for Multifunction USB Device (gpio, display, ...)

[Andy Shevchenko]

On Sun, Feb 16, 2020 at 7:30 PM Noralf Trønnes <noralf at tronnes.org> wrote:
>
> Hi,
>
> A while back I had the idea to turn a Raspberry Pi Zero into a $5
> USB to HDMI/SDTV/DSI/DPI display adapter.
>
> Thinking about how to represent the display to the driver I realised
> that hardware use registers as API. And Linux does have a generic
> register abstraction: regmap. Furthermore this means that if I can do a
> regmap over USB implementation, it will be easy to do other functions
> like gpio, adc and others. After a few iterations trying to understand
> the USB subsystem and satisfying driver requirements, I now have
> something that looks promising.
>
> I'm sending out an early version hoping to get feedback especially on
> the core parts that handles regmap and interrupts.
>
> Overview:
>
>           USB Host          :         USB Device
>                             :
>             --------------  :  ------------------
> ----------  | mfd: mud   |  :  | f_mud          |  ----------
> | Driver |  --------------  :  |                |  | Driver |
> ----------  | regmap-usb |  :  | (mud_regmap)   |  ----------
>             --------------  :  ------------------
>
>
> I've attached 2 drivers:
> - gpio/pinctrl: is more or less finished
> - display: needs a lot more work

Can regmap-usb be used for drivers/mfd/dln2.c for example?

-- 
With Best Regards,
Andy Shevchenko