[PATCH 1/6] bcm2835-gpio-exp: Driver for GPIO expander via mailbox service

[Michael Zoran]

On Thu, 2017-03-23 at 20:45 +0100, Stefan Wahren wrote:
> Hi Dave,
> 
> > Dave Stevenson <dave.stevenson at raspberrypi.org> hat am 23. März
> > 2017 um 18:08 geschrieben:
> > 
> > 
> > On 21 March 2017 at 20:58, Michael Zoran <mzoran at crowfest.net>
> > wrote:
> > > On Tue, 2017-03-21 at 23:30 +0300, Dan Carpenter wrote:
> > > > I've read Stefan's review comments and intervened where I
> > > > didn't
> > > > understand them.  The recent ones are very specific and
> > > > reasonable...
> > > > 
> > > > Just send a v2.  I don't get what the deal is...
> > > 
> > > Partly because Eric and Stefan have publically annouced all over
> > > the
> > > who knows where that they don't want this in staging.  They say
> > > it
> > > needs to go to the general tree.  So I'm not 100% sure a V2 makes
> > > sense
> > > when people aren't even agreeing if this is the correct place for
> > > this
> > > to be.
> > > 
> > > I did not write the driver myself, I've simply been burdened
> > > myself
> > > that VC4 doesn't really work that good on the RPI 3 so I was
> > > hoping it
> > > would unblock people after finding it on the web.
> > > 
> > > If people want a V2, then they are going to have to be very
> > > specific
> > > about what needs to change and exactly how it to change. Not just
> > > say
> > > they don't like it.
> > > 
> > > If it's suddenly so important, why can't someone else add in
> > > their
> > > corrections after my Signed-off-by: and add their own Signed-off-
> > > by:.
> > > Or better yet submit the original driver themselves.
> > 
> > Michael: I know the original request to upstream this came from
> > Phil /
> > myself, and thank you for your efforts. However if you want to
> > offload
> > this then I will find some time to go through a couple of
> > revisions.
> > It would be Tuesday or Wednesday next week all being well.
> > This is a pretty trivial driver so there's only limited scope for
> > me
> > messing it up (hopefully), and the lack of HDMI HPD is a stumbling
> > block for Pi3/CM3.
> > 
> > Can I get a couple of answers from others as to preferences first?
> > 
> > Sorry Eric, I wasn't aware you had previously sent a patch
> > implementing any of this otherwise I would have taken it as a base.
> > I'd seen a comment that you were thinking about it but that was
> > all.
> > So which patch is preferred as the base? Eric's or mine?
> > 
> > Eric's patch had the driver in the main tree vs Michael putting it
> > in
> > staging. Where do we really want this going?
> > Linus Walleij as one of the GPIO maintainers had reviewed Eric's
> > patch
> > and not totally dismissed it, so are we better off picking up on
> > the
> > comments from both review threads and aiming to merge directly to
> > drivers/gpio?
> > 
> > Linus' review comments preferred hard coding "ngpios" and
> > "firmware-gpio-offset" in the driver. Eric and Michael both pushed
> > them into DT. Stephan made a comment of setting rpi->gc.base
> > explicitly in the driver. I know I was focussed on the task of
> > getting
> > it working, hence the hardcoded gc.base=128 and then using gc.base
> > as
> > the firmware offset.
> > I can see cases for numerous options:
> > 1) Any expanders controlled through the firmware will start with an
> > offset of 128. Within the firmware GPIOs 0-127 map onto the
> > standard
> > GPIO block, but why would you bother to use this driver when you
> > can
> > go direct and avoid an IPC overhead? Hard coding that offset to 128
> > seems reasonable.
> 
> i think there is a big misunderstanding. There is no standard GPIO
> block. The base in mainline pinctrl-bcm2835 is -1, which means Linux
> is free to choose the base.
> 
> Btw userspace shouldn't rely on those GPIO numbers.
> 
> Stefan


Hay Guys,

You people have really done something with the bcm2835 platform that I
never, never thought would be possible.  Sometimes people say bad
things.  I'm still learning.

I had no idea you guys would be able to do with the platform what you
have been able to do. I'm very impressed, and yes I'm the one that
lacked the ability to think about side box here.

Someone once said a master processor would have to run at 1GHz to even
be competitive. Well, that has certainly been acomplished.