Re: Linux gnss driver SPI support?

[Johan Hovold <johan@kernel.org>]

On Wed, Jan 06, 2021 at 12:17:01PM -0800, Tim Harvey wrote:
> On Wed, Jan 6, 2021 at 3:21 AM Johan Hovold <johan@kernel.org> wrote:

> > Correct, there are currently no drivers supporting SPI and hence no
> > shared implementation either like there is for UART interfaces.
> >
> > The driver for your device would need to handle the SPI bits itself for
> > now. What kind of device is it?

> It is the u-blox ZOE-M8Q which has a UART as well as SPI/I2C/SQI
> interface. The particular board design we are working on is
> unfortunately out of UART's which is why we were looking at connecting
> it via SPI.

So we'd need to add support for the SPI interface to the ublox driver,
which is currently UART only.

> I did come across a posting about this [1] which uses a userspace app
> that creates a spy to pty bridge but it seems like they ran into some
> performance/latency issues.

Yeah, that is one of the problems that the gnss subsystem is meant to
solve; to handle the transport interface in the kernel and provide a
generic interface to user space.

Johan