linux-kernel - Re: [PATCH v7 1/5] staging: vc04_services: vchiq

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Date:   Tue, 20 Jun 2023 21:20:54 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Umang Jain <umang.jain@...asonboard.com>,
        linux-staging@...ts.linux.dev,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefan.wahren@...e.com,
        f.fainelli@...il.com, athierry@...hat.com, error27@...il.com,
        dave.stevenson@...pberrypi.com, kieran.bingham@...asonboard.com
Subject: Re: [PATCH v7 1/5] staging: vc04_services: vchiq_arm: Add new bus
 type and device type

On Tue, Jun 20, 2023 at 04:17:05PM +0200, Greg KH wrote:
> On Tue, Jun 20, 2023 at 07:11:48PM +0530, Umang Jain wrote:
> > The devices that the vchiq interface registers (bcm2835-audio,
> > bcm2835-camera) are implemented and exposed by the VC04 firmware.
> > The device tree describes the VC04 itself with the resources required
> > to communicate with it through a mailbox interface. However, the
> > vchiq interface registers these devices as platform devices. This
> > also means the specific drivers for these devices are getting
> > registered as platform drivers. This is not correct and a blatant
> > abuse of platform device/driver.
> > 
> > Add a new bus type, vchiq_bus_type and device type (struct vchiq_device)
> > which will be used to migrate child devices that the vchiq interfaces
> > creates/registers from the platform device/driver.
> > 
> > Signed-off-by: Umang Jain <umang.jain@...asonboard.com>
> > ---
> >  drivers/staging/vc04_services/Makefile        |  1 +
> >  .../interface/vchiq_arm/vchiq_device.c        | 78 +++++++++++++++++++
> >  .../interface/vchiq_arm/vchiq_device.h        | 43 ++++++++++
> >  3 files changed, 122 insertions(+)
> >  create mode 100644 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> >  create mode 100644 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> > 
> > diff --git a/drivers/staging/vc04_services/Makefile b/drivers/staging/vc04_services/Makefile
> > index 44794bdf6173..2d071e55e175 100644
> > --- a/drivers/staging/vc04_services/Makefile
> > +++ b/drivers/staging/vc04_services/Makefile
> > @@ -5,6 +5,7 @@ vchiq-objs := \
> >     interface/vchiq_arm/vchiq_core.o  \
> >     interface/vchiq_arm/vchiq_arm.o \
> >     interface/vchiq_arm/vchiq_debugfs.o \
> > +   interface/vchiq_arm/vchiq_device.o \
> >     interface/vchiq_arm/vchiq_connected.o \
> >  
> >  ifdef CONFIG_VCHIQ_CDEV
> > diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> > new file mode 100644
> > index 000000000000..e16279a25126
> > --- /dev/null
> > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> > @@ -0,0 +1,78 @@
> > +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
> 
> Code that directly interacts with the driver core can, for obvious
> reasons, not be BSD-3 licensed, sorry.
> 
> Also, why is any of this dual licensed?  What good is any of that?  In
> order for me to accept new dual-licensed code, it needs to be documented
> in the changelog very very well as to exactly why this is required, as
> the legal issues involved in maintaining dual-licensed code like this is
> tricky and easy to get wrong (as proven here already in this patch...)

The whole vchiq_arm layer is dual licensed GPL-2.0 + BSD-3. I assume
this is why Umang used the same licensing terms. We can use GPL-2.0 only
if this patch qualifies as original work and not derived work of the
existing code.

This being said, I have no objection changing the license of the whole
vchiq_arm layer to GPL-2.0 only. Dave, any opinion on this ?

-- 
Regards,

Laurent Pinchart