Re: [PATCH V7 1/4] drm: of: Add drm_of_get_dsi_bus helper function

From: Maxime Ripard <maxime@cerno.tech>
To: Chris Morgan <macroalpha82@gmail.com>
Cc: dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
	linux-rockchip@lists.infradead.org, maccraft123mc@gmail.com,
	tzimmermann@suse.de, maarten.lankhorst@linux.intel.com,
	heiko@sntech.de, krzysztof.kozlowski+dt@linaro.org,
	robh+dt@kernel.org, daniel@ffwll.ch, airlied@gmail.com,
	sam@ravnborg.org, thierry.reding@gmail.com,
	linus.walleij@linaro.org, Chris Morgan <macromorgan@hotmail.com>
Subject: Re: [PATCH V7 1/4] drm: of: Add drm_of_get_dsi_bus helper function
Date: Wed, 4 Jan 2023 13:40:10 +0100	[thread overview]
Message-ID: <20230104124010.6rambtw7mzg7sycv@houat> (raw)
In-Reply-To: <20230103190707.104595-2-macroalpha82@gmail.com>

Hi,

On Tue, Jan 03, 2023 at 01:07:04PM -0600, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add helper function to find DSI host for devices where DSI panel is not
> a minor of a DSI bus (such as the Samsung AMS495QA01 panel or the
> official Raspberry Pi touchscreen display).
> 
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/gpu/drm/drm_of.c | 62 ++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_of.h     | 11 +++++++
>  2 files changed, 73 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 7bbcb999bb75..7d89ac164069 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -10,6 +10,7 @@
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_encoder.h>
> +#include <drm/drm_mipi_dsi.h>
>  #include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  
> @@ -493,3 +494,64 @@ int drm_of_get_data_lanes_count_ep(const struct device_node *port,
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(drm_of_get_data_lanes_count_ep);
> +
> +/**
> + * drm_of_get_dsi_bus - find the DSI bus for a given device
> + * @dev: parent device of display (SPI, I2C)
> + * @dsi_host: DSI host to be populated
> + * @info: DSI device info to be updated with correct DSI node

Why aren't we returning the dsi_host through an ERR_PTR? All the DRM
accessors with get return the pointer directly, I'd rather stick to
that.

> + * Given a panel device parented to a non-DSI device, follow the
> + * devicetree to find the correct DSI host node and populate the
> + * dsi_host with the correct host and info with the correct node.

I think we could make that a bit clearer using something like:

Gets parent DSI bus for a DSI device controlled through a bus other than
MIPI-DCS (SPI, I2C, etc.) using the Device Tree.

> + * Returns zero if successful, -EPROBE_DEFER if the DSI host is
> + * found but not available, or -ENODEV otherwise.
> + */

> +int drm_of_get_dsi_bus(struct device *dev,
> +			      struct mipi_dsi_host **dsi_host,
> +			      struct mipi_dsi_device_info *info)

The arguments are not aligned.

Maxime

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