linux-kernel - Re: [PATCH v4 2/6] drm/dsi: Refactor device creation

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Message-ID: <20160121154605.GB647@ulmo.nvidia.com>
Date:	Thu, 21 Jan 2016 16:46:07 +0100
From:	Thierry Reding <treding@...dia.com>
To:	Archit Taneja <architt@...eaurora.org>
CC:	<dri-devel@...ts.freedesktop.org>, <a.hajda@...sung.com>,
	<jani.nikula@...ux.intel.com>, <linux-kernel@...r.kernel.org>,
	<airlied@...ux.ie>, <daniel@...ll.ch>, <l.stach@...gutronix.de>,
	<robh@...nel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v4 2/6] drm/dsi: Refactor device creation

On Thu, Dec 10, 2015 at 06:11:36PM +0530, Archit Taneja wrote:
> Simplify the mipi dsi device creation process. device_initialize and

"MIPI" and "DSI", please.

> device_add don't need to be called separately when creating
> mipi_dsi_device's. Use device_register instead to simplify things.
> 
> Create a helper function mipi_dsi_device_new which takes in struct
> mipi_dsi_device_info and mipi_dsi_host. It clubs the functions
> mipi_dsi_device_alloc and mipi_dsi_device_add into one.
> 
> mipi_dsi_device_info acts as a template to populate the dsi device
> information. This is populated by of_mipi_dsi_device_add and passed to
> mipi_dsi_device_new.
> 
> Later on, we'll provide mipi_dsi_device_new as a standalone way to create
> a dsi device not available via DT.
> 
> The new device creation process tries to closely follow what's been done
> in i2c_new_device in i2c-core.
> 
> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> Signed-off-by: Archit Taneja <architt@...eaurora.org>
> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 61 +++++++++++++++++-------------------------
>  include/drm/drm_mipi_dsi.h     | 15 +++++++++++
>  2 files changed, 40 insertions(+), 36 deletions(-)

To be honest, I'm not sure I like this. If you want to have a simpler
helper, why not implement it using the lower-level helpers. Really the
only thing you're doing here is add a high-level helper that takes an
info struct, whereas previously the same would be done by storing the
info directly in the structure between allocation and addition of the
device.

Initially the implementation was following that of platform devices, I
see no reason to deviate from that. What you want here can easily be
done by something like:

	struct mipi_dsi_device *
	mipi_dsi_device_register_full(struct mipi_dsi_host *host,
				      const struct mipi_dsi_device_info *info)
	{
		struct mipi_dsi_device *dsi;

		dsi = mipi_dsi_device_alloc(host);
		if (IS_ERR(dsi))
			return dsi;

		dsi->dev.of_node = info->node;
		dsi->channel = info->channel;

		err = mipi_dsi_device_add(dsi);
		if (err < 0) {
			...
		}

		return dsi;
	}

Thierry

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