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From:   Min Li <min.li.xe@renesas.com>
To:     Greg KH <gregkh@linuxfoundation.org>
CC:     "arnd@arndb.de" <arnd@arndb.de>,
        "derek.kiernan@xilinx.com" <derek.kiernan@xilinx.com>,
        "dragan.cvetic@xilinx.com" <dragan.cvetic@xilinx.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "lee.jones@linaro.or" <lee.jones@linaro.or>
Subject: RE: [PATCH misc v2 2/2] misc: Add Renesas Synchronization Management
 Unit (SMU) support
Thread-Topic: [PATCH misc v2 2/2] misc: Add Renesas Synchronization Management
 Unit (SMU) support
Thread-Index: AQHXqmIqGzfEPA/ASUKU/78egiaTO6umId8AgACkSYCAAAc7gIAAAX9ggAAFoACAAA5yMA==
Date:   Thu, 16 Sep 2021 17:01:10 +0000
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> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: September 16, 2021 12:05 PM
> To: Min Li <min.li.xe@renesas.com>
> Cc: arnd@arndb.de; derek.kiernan@xilinx.com; dragan.cvetic@xilinx.com;
> linux-kernel@vger.kernel.org; lee.jones@linaro.or
> Subject: Re: [PATCH misc v2 2/2] misc: Add Renesas Synchronization
> Management Unit (SMU) support
>=20
> On Thu, Sep 16, 2021 at 03:54:52PM +0000, Min Li wrote:
> > >
> > > Please put that link in the changelog comment and in the .c code as
> > > well so that people know where to find it.
> > >
> > > > >
> > > > > Why is this new api not a standard one?
> > > > >
> > > >
> > > > There is no actual standard for the GNSS assisted partial timing
> > > > support (APTS) In terms of Linux kernel API
> > >
> > > Then make one!  :)
> >
> > Yes it is on our roadmap to do that for next release
>=20
> Please do it for this kernel api, otherwise you have to support this for =
the
> next 20+ years as-is :(
>=20

In that case, I would have to get back to you in a few months. If you are r=
ejecting this
change due to this reason. Please tell me explicitly so that I can copy pas=
te to my manager
and that would be it. Thanks=20

> > > Why not just do this all from userspace then?  You can have spi/i2c
> > > userspace code, right?  Why does this have to be a kernel driver?
> > >
> > We used to do everything in userspace. But since PHC (ptp hardware
> > clock) came along, we decided to move the driver part to kernel. Please
> take a look at drivers/ptp/ptp_clockmatrix.c for reference.
> > Recently, we have some functions like APTS that doesn't belong to PTP
> > or anything else so we have to split those functions to RSMU misc drive=
r
> and i2c/spi bus accesses to RSMU MFD driver.
>=20
> I still do not understand why this has to be a kernel driver, sorry.
> What exactly forces it to be that way?
>=20
That is our management decision since everyone is trying to move their driv=
er to Linux kernel
to contribute so that we don't have to release the driver to each customer =
separately. The customer
can just grab the driver from linux