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
USB3 device I've only tested this with usb2 devices (Pi, BBB) so I should get myself a usb3 gadget capable board. My searching didn't turn up much, so this seems to be quite rare. ROCK960 has USB 3.0 type C OTG but the price is $139 which is a bit expensive for this hobby project. Does anyone know of a cheap board?
Noralf.
Noralf Trønnes (9): regmap: Add USB support mfd: Add driver for Multifunction USB Device usb: gadget: function: Add Multifunction USB Device support pinctrl: Add Multifunction USB Device pinctrl driver usb: gadget: function: mud: Add gpio support regmap: Speed up _regmap_raw_write_impl() for large buffers drm: Add Multifunction USB Device display driver drm/client: Add drm_client_init_from_id() and drm_client_modeset_set() usb: gadget: function: mud: Add display support
drivers/base/regmap/Kconfig | 8 +- drivers/base/regmap/Makefile | 1 + drivers/base/regmap/regmap-usb.c | 1026 ++++++++++++++++++ drivers/base/regmap/regmap.c | 10 +- drivers/gpu/drm/Kconfig | 2 + drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_client.c | 37 + drivers/gpu/drm/drm_client_modeset.c | 52 + drivers/gpu/drm/mud/Kconfig | 18 + drivers/gpu/drm/mud/Makefile | 4 + drivers/gpu/drm/mud/mud_drm.c | 1198 ++++++++++++++++++++++ drivers/gpu/drm/mud/mud_drm.h | 137 +++ drivers/gpu/drm/mud/mud_drm_gadget.c | 889 ++++++++++++++++ drivers/mfd/Kconfig | 8 + drivers/mfd/Makefile | 1 + drivers/mfd/mud.c | 580 +++++++++++ drivers/pinctrl/Kconfig | 9 + drivers/pinctrl/Makefile | 1 + drivers/pinctrl/pinctrl-mud.c | 657 ++++++++++++ drivers/pinctrl/pinctrl-mud.h | 89 ++ drivers/usb/gadget/Kconfig | 36 + drivers/usb/gadget/function/Makefile | 6 + drivers/usb/gadget/function/f_mud.c | 913 +++++++++++++++++ drivers/usb/gadget/function/f_mud.h | 210 ++++ drivers/usb/gadget/function/f_mud_drm.c | 181 ++++ drivers/usb/gadget/function/f_mud_pins.c | 962 +++++++++++++++++ drivers/usb/gadget/function/mud_regmap.c | 936 +++++++++++++++++ include/drm/drm_client.h | 4 + include/linux/mfd/mud.h | 16 + include/linux/regmap.h | 23 + include/linux/regmap_usb.h | 97 ++ 31 files changed, 8107 insertions(+), 5 deletions(-) create mode 100644 drivers/base/regmap/regmap-usb.c create mode 100644 drivers/gpu/drm/mud/Kconfig create mode 100644 drivers/gpu/drm/mud/Makefile create mode 100644 drivers/gpu/drm/mud/mud_drm.c create mode 100644 drivers/gpu/drm/mud/mud_drm.h create mode 100644 drivers/gpu/drm/mud/mud_drm_gadget.c create mode 100644 drivers/mfd/mud.c create mode 100644 drivers/pinctrl/pinctrl-mud.c create mode 100644 drivers/pinctrl/pinctrl-mud.h create mode 100644 drivers/usb/gadget/function/f_mud.c create mode 100644 drivers/usb/gadget/function/f_mud.h create mode 100644 drivers/usb/gadget/function/f_mud_drm.c create mode 100644 drivers/usb/gadget/function/f_mud_pins.c create mode 100644 drivers/usb/gadget/function/mud_regmap.c create mode 100644 include/linux/mfd/mud.h create mode 100644 include/linux/regmap_usb.h