On 3/20/24 01:02, Andrew Lunn wrote:
Yes, after discussion with Vaishnav and trying to brainstorm some way to do
the same thing with dt overlays, it seems that trying to use dt overlays
will mean need to have completely separate implementation of mikroBUS for
local ports and mikroBUS over greybus.
Could you explain why please?
Are greybus I2C bus masters different from physical I2C bus masters?
Are greybus SPI bus masters different from physical SPI bus masters?
Well, they are virtual, so they are not declared in the device tree. I
have linked the greybus i2c implementation. It basically allocates an
i2c_adpater and then adds it using `i2c_add_adapter` method. This
adapter can then be passed to say mikroBUS driver where it can be used
as a normal i2c_adapter, and we can register the device to it.
Additionally, trying to put dt overlays in EEPROM would mean they
will be incompatible with use in local ports and vice versa.
I don't think you need to put the DT overlay in the EEPROM. All you
need to do is translate the manifest into DT for those simple devices
which can be described by the limited manifest format. For more
complex devices, you use the ID to go find a DT fragment which
describes the board, and skip the manifest to DT transformation.
Andrew
I am not familiar enough to know if the device tree can work with
virtual devices created by greybus subsystem.
Maybe the problem stems from the fact that mikroBUS does not have a
physical controller (and my inability to explain the patch properly).
However, the purpose of this patchset is to in fact provide a virtual
mikroBUS controller to allow us to register a mikroBUS addon board
described by board_info struct similar to how it is possible to create
and register an i2c device on an i2c adapter using
`i2c_new_client_device` or spi device using `spi_new_device`. The
manifest is used to populate this board_info struct, but it will be
possible to use something other than mikroBUS manifest if someone wants
to. I can make the necessary adjustments by moving manifest support to
its own config option.
Link:
https://elixir.bootlin.com/linux/latest/source/drivers/staging/greybus/i2c.c#L230
Greybus i2c
Ayush Singh
