Re: Using SPI devices from userspace on the RPI, or from anything NetBSD for that matter?

[Brad Spencer <brad%anduin.eldar.org@localhost>]

Brian Buhrow <buhrow%nfbcal.org@localhost> writes:

> 	hello.  I'm working on a project where I think I'll be wanting to talk
> to an SPI connected LCD or LED display on an Rasberry Pi.  What I envision
> doing with it shouldn't require a kernel level driver given the fact that
> we already have the SPI(4) framework.  My question is, how can a user-space
> program  read from or write to  a SPI connected peripheral?  I've found the
> gpioctl(8) program and gpio( devices for talking to GPIO connected devices,
> but I don't see how to speak to SPI connected things.  Can anyone enlighten
> me?  I realize I may be asking a very elementary question, but my
> documentation searches haven't revealed what I want for NetBSD.  I've found
> such documents for Linux, but I'd really like to use NetBSD for this
> project.
>
> Any thoughts would be greatly appreciated.
> -thanks
> -Brian


Hello...

As a general statement, I don't think that the SPI bus is exposed to
userland in the manor you desire.  SPI and IIC, I think, are both kernel
level interfaces at this point and if you need to use them, I believe
you are looking at a kernel driver of some sort.  Even if it is just a
simple one that lets you poke the bus and/or device.

Also note that gpioctl really does not allow arbitrary access to the
gpio pins.  You can configure the direction, read and write to them, and
you can attach a driver but you can't really talk to the gpio bus
directly from userland except as a ioctl end point to do the
configuration, reading and writing.

The exception to this may be spiflash which appears to present a device
for working with those sorts of things, but that isn't a general SPI bus
device.



-- 
Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS
http://anduin.eldar.org  - & -  http://anduin.ipv6.eldar.org [IPv6 only]