linux-kernel - Re: [PATCH v4 6/6] drm/komeda: Expose side_by_side by sysfs/config

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Date:   Fri, 22 Nov 2019 05:16:29 +1000
From:   Dave Airlie <airlied@...il.com>
To:     "james qian wang (Arm Technology China)" <james.qian.wang@....com>
Cc:     Liviu Dudau <Liviu.Dudau@....com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        Brian Starkey <Brian.Starkey@....com>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>,
        Mihail Atanassov <Mihail.Atanassov@....com>, nd <nd@....com>,
        "Oscar Zhang (Arm Technology China)" <Oscar.Zhang@....com>,
        "Tiannan Zhu (Arm Technology China)" <Tiannan.Zhu@....com>,
        "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Julien Yin (Arm Technology China)" <Julien.Yin@....com>,
        "Channing Chen (Arm Technology China)" <Channing.Chen@....com>,
        "Thomas Sun (Arm Technology China)" <thomas.Sun@....com>,
        "Lowry Li (Arm Technology China)" <Lowry.Li@....com>,
        Ben Davis <Ben.Davis@....com>
Subject: Re: [PATCH v4 6/6] drm/komeda: Expose side_by_side by sysfs/config_id

On Thu, 21 Nov 2019 at 20:21, james qian wang (Arm Technology China)
<james.qian.wang@....com> wrote:
>
> On Thu, Nov 21, 2019 at 10:49:26AM +0100, Daniel Vetter wrote:
> > On Thu, Nov 21, 2019 at 07:12:55AM +0000, james qian wang (Arm Technology China) wrote:
> > > There are some restrictions if HW works on side_by_side, expose it via
> > > config_id to user.
> > >
> > > Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@....com>
> > > ---
> > >  drivers/gpu/drm/arm/display/include/malidp_product.h | 3 ++-
> > >  drivers/gpu/drm/arm/display/komeda/komeda_dev.c      | 1 +
> > >  2 files changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/arm/display/include/malidp_product.h b/drivers/gpu/drm/arm/display/include/malidp_product.h
> > > index 1053b11352eb..96e2e4016250 100644
> > > --- a/drivers/gpu/drm/arm/display/include/malidp_product.h
> > > +++ b/drivers/gpu/drm/arm/display/include/malidp_product.h
> > > @@ -27,7 +27,8 @@ union komeda_config_id {
> > >                     n_scalers:2, /* number of scalers per pipeline */
> > >                     n_layers:3, /* number of layers per pipeline */
> > >                     n_richs:3, /* number of rich layers per pipeline */
> > > -                   reserved_bits:6;
> > > +                   side_by_side:1, /* if HW works on side_by_side mode */
> > > +                   reserved_bits:5;
> > >     };
> > >     __u32 value;
> > >  };
> > > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> > > index c3fa4835cb8d..4dd4699d4e3d 100644
> > > --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> > > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> > > @@ -83,6 +83,7 @@ config_id_show(struct device *dev, struct device_attribute *attr, char *buf)
> >
> > Uh, this sysfs file here looks a lot like uapi for some compositor to
> > decide what to do. Do you have the userspace for this?
>
> Yes, our HWC driver uses this config_id and product_id for identifying the
> HW caps.
>

This seems like it should be done more in the kernel, why does
userspace needs all that info, to make more informed decisions?

How would drm_hwcomposer get the same result?

I'd prefer we just remove the sysfs nodes from upstream unless we have
an upstream user for them.

Dave.