linux-kernel - Re: [PATCH v2 5/6] ACPI: scan: Extract MIPI DiSco for Imaging data into swnodes

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Message-ID: <ZUEIb81Bbzgvf2Uf@kekkonen.localdomain>
Date:   Tue, 31 Oct 2023 14:00:15 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/6] ACPI: scan: Extract MIPI DiSco for Imaging data
 into swnodes

Hi Rafael,

On Tue, Oct 31, 2023 at 02:46:51PM +0100, Rafael J. Wysocki wrote:
> Hi Sakari,
> 
> On Tue, Oct 31, 2023 at 11:33 AM Sakari Ailus
> <sakari.ailus@...ux.intel.com> wrote:
> >
> > Hi Rafael,
> >
> > On subject:
> >
> > s/DiSco/DisCo/
> 
> Huh
> 
> Thanks for catching this!
> 
> > On Fri, Oct 20, 2023 at 04:39:27PM +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >
> > > Add information extracted from the MIPI DiSco for Imaging device
> >
> > Ditto.
> >
> > > properties to software nodes created during the CSI-2 connection graph
> > > discovery.
> > >
> > > Link: https://www.mipi.org/specifications/mipi-di
> >
> > This URL is broken. The correct URL is:
> >
> >         https://www.mipi.org/specifications/mipi-disco-imaging
> 
> OK
> 
> > > Co-developed-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > > Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > ---
> > >  drivers/acpi/internal.h |    1
> > >  drivers/acpi/mipi-di.c  |  240 +++++++++++++++++++++++++++++++++++++++++++++++-
> >
> > How about mipi-disco.c? I wouldn't mind having mipi-disco-imaging.c either.
> 
> Well, mipi-disco-imaging is a bit too long and the meaning of
> mipi-disco would not be clear IMO.
> 
> What about mipi-disco-img?

Seems fine to me.

> 
> [cut]
> 
> > > +     ret = fwnode_property_count_u8(port_fwnode, "mipi-img-lane-polarities");
> > > +     if (ret > 0) {
> > > +             unsigned long mask;
> > > +             unsigned int i;
> > > +
> > > +             /*
> > > +              * Total number of lanes here is clock lane + data lanes.
> > > +              * Require that number to be low enough so they all can be
> > > +              * covered by the bits in one byte.
> > > +              */
> > > +             BUILD_BUG_ON(BITS_PER_TYPE(u8) <= ARRAY_SIZE(port->data_lanes));
> > > +
> > > +             fwnode_property_read_u8_array(port_fwnode,
> > > +                                           "mipi-img-lane-polarities",
> > > +                                           val, 1);
> > > +
> > > +             for (mask = val[0], i = 0; i < num_lanes + 1; i++)
> > > +                     port->lane_polarities[i] = test_bit(i, &mask);
> >
> > This works only up to seven lanes.
> 
> True, but then ACPI_DEVICE_CSI2_DATA_LANES is defined as 4.

The spec has no limit and in practice 4 is relatively common while 8 exists
(but is somewhat rare). I actually think it'd be a good idea to bump this
to 8 already.

-- 
Regards,

Sakari Ailus