linux-kernel - Re: [RFC PATCH] Add bridge driver to connect sensors to CIO2 device via software nodes on ACPI platforms

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Date:   Thu, 17 Sep 2020 17:14:00 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Dan Scally <djrscally@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Yong Zhi <yong.zhi@...el.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tian Shu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        "open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
        jorhand@...ux.microsoft.com, Tsuchiya Yuto <kitakar@...il.com>,
        kieran.bingham@...asonboard.com
Subject: Re: [RFC PATCH] Add bridge driver to connect sensors to CIO2 device
 via software nodes on ACPI platforms

On Thu, Sep 17, 2020 at 4:53 PM Dan Scally <djrscally@...il.com> wrote:
>
> Hi Andy, thanks for input (as always)

You're welcome! I'm really impressed by your activity in this area.

> On 17/09/2020 13:45, Andy Shevchenko wrote:
> > On Thu, Sep 17, 2020 at 11:52:28AM +0100, Dan Scally wrote:
> >> On 17/09/2020 11:33, Sakari Ailus wrote:

To the point of placement, I think this should go under
drivers/platform/x86 (Adding Hans and Mark, who can express their
opinions).

...

> > Ah, I think you misinterpreted the meaning of above. The above is a switch how
> > camera device appears either as PCI or an ACPI. So, it effectively means you
> > should *not* have any relation for this HID until you find a platform where the
> > device is for real enumerated via ACPI.
> >
> Ah, ok. So that was never going to work. Thanks. That does raise another
> question; we have had some testers report failure, which turns out to be
> because on their platforms the definition of their cameras in ACPI is
> never translated into an i2c_client so the cio2-bridge doesn't bind.
> Those have a similar conditional in the _STA method, see CAM1 in this
> DSDT for example:
> https://raw.githubusercontent.com/linux-surface/acpidumps/master/surface_go/dsdt.dsl.
> Is there anything we can do to enable those cameras to be discovered too?

It means that this

...

> >>>> +#define PROPERTY_ENTRY_NULL                       \
> >>>> +((const struct property_entry) { })
> >>> Alignment. Same appears to apply to other macros (please indent).
> >> Yep
> >>>> +#define SOFTWARE_NODE_NULL                        \
> >>>> +((const struct software_node) { })
> > Why?!
> >
> It felt ugly to have the other definitions be macros and not this one,
> but I can change it.

My point is that those macros are simply redundant. The point is to
have a terminator record (all 0:s in the last entry of an array) which
is usually being achieved by allocating memory with kcalloc() which
does implicitly this for you.

-- 
With Best Regards,
Andy Shevchenko