Re: [PATCH v4 6/6] drm/komeda: Expose side_by_side by sysfs/config_id

From: Dave Airlie <airlied@gmail.com>
To: "james qian wang (Arm Technology China)" <james.qian.wang@arm.com>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>,
	"airlied@linux.ie" <airlied@linux.ie>,
	Brian Starkey <Brian.Starkey@arm.com>,
	"maarten.lankhorst@linux.intel.com" 
	<maarten.lankhorst@linux.intel.com>,
	Mihail Atanassov <Mihail.Atanassov@arm.com>, nd <nd@arm.com>,
	"Oscar Zhang (Arm Technology China)" <Oscar.Zhang@arm.com>,
	"Tiannan Zhu (Arm Technology China)" <Tiannan.Zhu@arm.com>,
	"Jonathan Chai (Arm Technology China)" <Jonathan.Chai@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"Julien Yin (Arm Technology China)" <Julien.Yin@arm.com>,
	"Channing Chen (Arm Technology China)" <Channing.Chen@arm.com>,
	"Thomas Sun (Arm Technology China)" <thomas.Sun@arm.com>,
	"Lowry Li (Arm Technology China)" <Lowry.Li@arm.com>,
	Ben Davis <Ben.Davis@arm.com>
Subject: Re: [PATCH v4 6/6] drm/komeda: Expose side_by_side by sysfs/config_id
Date: Fri, 22 Nov 2019 05:16:29 +1000	[thread overview]
Message-ID: <CAPM=9tw8KDh1bkErYXGsc1Yvc0H9NEEUJ3eA0BSqgGOWDaPhxg@mail.gmail.com> (raw)
In-Reply-To: <20191121102101.GA32514@jamwan02-TSP300>

On Thu, 21 Nov 2019 at 20:21, james qian wang (Arm Technology China)
<james.qian.wang@arm.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@arm.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.