[PATCH v4 2/6] Add GPIO ioctl decoding

[Kent Gibson]

On Mon, Jan 25, 2021 at 10:59:18AM +0800, Kent Gibson wrote:
> On Mon, Jan 25, 2021 at 05:44:50AM +0300, Dmitry V. Levin wrote:
> > On Mon, Jan 25, 2021 at 09:48:38AM +0800, Kent Gibson wrote:
> > [...]
> > > What I'm suggesting is keeping a copy of the current linux/gpio.h in the
> > > strace tree so we always build against that - even when building on old
> > > kernels.  The decoder and tests would match that specific header, but
> > > build on any kernel.
> > > 
> > > Granted this doesn't work for any headers that may have ABI issues, but
> > > that isn't the case for gpio.h - all the types have remained ABI
> > > compatible since inception.  And that is why we needed to do a v2 as
> > > those types were unable to be extended.
> > > 
> > > The biggest problem I have is where to put it, as the types directory
> > > serves a different purpose.
> > 
> > Yes, this is technically possible to place it into "linux/gpio.h".
> > The license of this header is "GPL-2.0 WITH Linux-syscall-note" which
> > means that it "can be included into non GPL compliant user space
> > application code", so I don't see any license issues here. 
> > 
> > This was not always the case, before commit v4.14-rc8~25^2 the license of
> > linux/gpio.h was GPL-2.0-only (i.e. without Linux-syscall-note exception)
> > which meant it couldn't be included without making the whole project
> > GPL-2.0-only.
> 
> Hmmm, I thought API headers were open for copying either way.
> 
> > 
> > Maybe it's time to reconsider our policy of not copying Linux header
> > files.
> > 
> 
> I'm was playing with your ldv/gpio branch, and have added the linux
> gpio.h into types/linux/gpio.h, switched gpio_ioctl.c and ioctl_gpio.c
> over to use those standard types, and removed types/gpio.h and
> xlat/gpio_ioctl_cmds.in.
> 
> The result seems a whole lot simpler to me.
> 
> Btw, I went with types/linux/gpio.h to make the distinction between the
> <linux/gpio.h> and "linux/gpio.h> clearer, but can easily relocate that.
> 
> I'll push a copy to my github later if you want to take a closer look
> - other things have priority at the moment.
> 

I've pushed my latest changes to the ldv/gpio branch in my github strace
fork [1].  Obviously not intending you to pull that - just for
comparision.

I've also popped of a mail on the licencing issue to the GPIO mailing
list, as libgpiod recently switched to including the latest header in
its source tree to ease build issues, and it is also LGPL 2.1 so the
same issue applies there.

Cheers,
Kent.

[1] https://github.com/warthog618/strace/tree/ldv/gpio