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

From: Daniel Vetter <daniel@ffwll.ch>
To: "james qian wang (Arm Technology China)"
	<james.qian.wang@arm.com>, Dave Airlie <airlied@gmail.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: Thu, 21 Nov 2019 10:49:26 +0100	[thread overview]
Message-ID: <20191121094926.GC6236@phenom.ffwll.local> (raw)
In-Reply-To: <20191121071205.27511-7-james.qian.wang@arm.com>

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?

Also a few more thoughts on this:
- You can't just add more fields to uapi structs.
- This doesn't really feel like it was ever reviewed to fit into atomic.
- sysfs should be one value per file, not a smorgasbrod of things stuffed
  into a binary structure.
-Daniel

>  	memset(&config_id, 0, sizeof(config_id));
>  
>  	config_id.max_line_sz = pipe->layers[0]->hsize_in.end;
> +	config_id.side_by_side = mdev->side_by_side;
>  	config_id.n_pipelines = mdev->n_pipelines;
>  	config_id.n_scalers = pipe->n_scalers;
>  	config_id.n_layers = pipe->n_layers;
> -- 
> 2.20.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch