[OpenWrt-Devel] [PATCH] [kernel] cp201x: Add GPIO ioctl commands (from Silicon Labs)

Ted Hess thess at kitschensync.net
Fri Aug 7 21:53:12 EDT 2015

Thanks for the info and explanation. No need for the pointers.

I'd already decided on dropping this request 'cause it did seem a bit hacky and was looking at a better solution. Your suggestion to 
take a look at libusb seems like a good thing to do for this app.


-----Original Message----- 
From: Karl Palsson
Sent: Friday, August 07, 2015 9:14 PM
To: Ted Hess
Cc: Felix Fietkau ; OpenWrt developers
Subject: Re: Re: [OpenWrt-Devel] [PATCH] [kernel] cp201x: Add GPIO ioctl commands (from Silicon Labs)

Hash: SHA1

"Ted Hess" <thess at kitschensync.net> wrote:
> After a bit more research - This is what I know:
> The upstream cp210x driver is not completely up-to-date with the driver
> silabs maintains on
> their site. In their own words: "... unfortunately GPIO is not something
> that has been
> committed to the Linux kernel yet for community maintenance. We leave
> the drivers on our
> website, even though they are a bit behind the curve of the maintained
> kernels, to
> demonstrate how to do this quickly using an ioctl() call."
> I also noted that the patch I submitted is not up-to-date with their
> latest devices which are
> supported in their driver - whoops.
> I could try to submit this upstream even if it was snatched from their
> driver. Is this OK?

There 's two people working on this on the linux-usb mailing list "right
now"  (I'm on apalling internet right now, so I can't find links for you
to the archives)  The ioctl approach has been totally vetoed, any ioctl
for gpios on this chips will never merge upstream, the silabs driver is
for people who don't care about those sorts of things.  gpios for ftdi
is also landing, and it's finally being accepted that all of these
things are actually, you know, important, so it's finally getting there,
but the ioctl approach is out.  I wouldn't personally be a fan of
openwrt putting in ioctls even for "just for now" as it's something you
can maintain in your own tree if you really need this sort of

> There is a small relay controller package (crelay) that I am going to
> submit to the packages
> repo it this patch gets accepted. It uses the cp210x ioctl interface.

What's happening is it's getting the whole gpiolib interface.  so this
app will only ever work with people using the vendor driver.... _if_ you
need to do it in the kernel.  You can always use libusb to make the same
control requests if you like, and if you're only poking a relay, I'd
imagine it's more than sufficient.  (of course depending on what you
want to be doing at the same time and all that)

Karl P

> -----Original Message----- 
> From: Felix Fietkau
> Sent: Monday, August 03, 2015 2:33 PM
> To: Ted Hess ; OpenWrt developers
> Subject: Re: [OpenWrt-Devel] [PATCH] [kernel] cp201x: Add GPIO ioctl
> commands (from Silicon Labs)
> On 2015-08-03 20:17, Ted Hess wrote:
> > It would probably make sense to do it that way however, there are apps which already use the ioctl interface on this device and
> > this
> > code came directly from the the manufacturer's linux driver.
> >
> > I'm not sure how to add general GPIO support for a specific USB device? Things to research...
> Did the manufacturer submit this upstream already, or is somebody else
> (maybe you) going to do so?
> - Felix
> _______________________________________________
> openwrt-devel mailing list
> openwrt-devel at lists.openwrt.org
> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel

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