Message-ID: <610f6023-04ea-0209-0038-05ae9b9ea58e@linaro.org>
Date:   Mon, 22 May 2023 10:55:00 +0200
From:   neil.armstrong@...aro.org
To:     Paulo Pavacic <pavacic.p@...il.com>, sam@...nborg.org,
        airlied@...il.com, daniel@...ll.ch, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/panel-fannal-c3004: Add fannal c3004 DSI panel

Hi,

On 19/05/2023 16:24, Paulo Pavacic wrote:
> 
> Fannal C3004 is a 480x800 display made by fannal that requires
> DCS initialization sequences.
> 
> Signed-off-by: Paulo Pavacic <pavacic.p@...il.com>
> ---
> v2 changelog:
>   - renamed from panel-mipi-dsi-bringup
>   - only one MAINTAINER e-mail
> ---
>   MAINTAINERS                                |   1 +
>   drivers/gpu/drm/panel/Kconfig              |  11 +
>   drivers/gpu/drm/panel/Makefile             |   1 +
>   drivers/gpu/drm/panel/panel-fannal-c3004.c | 405 +++++++++++++++++++++
>   4 files changed, 418 insertions(+)
>   create mode 100644 drivers/gpu/drm/panel/panel-fannal-c3004.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 62374c8424b9..93fc1ae6832f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6432,6 +6432,7 @@ M:	Paulo Pavacic <pavacic.p@...il.com>
>   S:	Maintained
>   C:	matrix:r/mipi-dsi-bringup:matrix.org
>   F:	Documentation/devicetree/bindings/display/panel/panel-fannal,c3004.yaml
> +F:	drivers/gpu/drm/panel/panel-fannal-c3004.c
>   
>   DRM DRIVER FOR FARADAY TVE200 TV ENCODER
>   M:	Linus Walleij <linus.walleij@...aro.org>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 2b9d6db7860b..a1041c1e6bf6 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -144,6 +144,17 @@ config DRM_PANEL_ELIDA_KD35T133
>   	  KD35T133 controller for 320x480 LCD panels with MIPI-DSI
>   	  system interfaces.
>   
> +config DRM_PANEL_FANNAL_C3004
> +	tristate "Fannal C3004 panel"
> +	depends on OF
> +	depends on DRM_MIPI_DSI
> +	help
> +	  Say Y here if you want to enable support for the Fannal C3004
> +	  2-lane 480x800 MIPI DSI panel which requires initialization
> +	  sequence.
> +
> +	  If M is selected the module will be called panel-fannal-c3004.
> +
>   config DRM_PANEL_FEIXIN_K101_IM2BA02
>   	tristate "Feixin K101 IM2BA02 panel"
>   	depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index ff169781e82d..13c0f00038b5 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
>   obj-$(CONFIG_DRM_PANEL_EDP) += panel-edp.o
>   obj-$(CONFIG_DRM_PANEL_EBBG_FT8719) += panel-ebbg-ft8719.o
>   obj-$(CONFIG_DRM_PANEL_ELIDA_KD35T133) += panel-elida-kd35t133.o
> +obj-$(CONFIG_DRM_PANEL_FANNAL_C3004) += panel-fannal-c3004.o
>   obj-$(CONFIG_DRM_PANEL_FEIXIN_K101_IM2BA02) += panel-feixin-k101-im2ba02.o
>   obj-$(CONFIG_DRM_PANEL_FEIYANG_FY07024DI26A30D) += panel-feiyang-fy07024di26a30d.o
>   obj-$(CONFIG_DRM_PANEL_HIMAX_HX8394) += panel-himax-hx8394.o
> diff --git a/drivers/gpu/drm/panel/panel-fannal-c3004.c b/drivers/gpu/drm/panel/panel-fannal-c3004.c
> new file mode 100644
> index 000000000000..decbd0c59093
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-fannal-c3004.c
> @@ -0,0 +1,405 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * MIPI DSI driver for Fannal C3004.
> + * Copyright (C) 2023, Zenitel
> + * Author: Paulo Pavacic <pavacic.p@...il.com>
> + */
> +
> +// ↓ include headers, static values, static functions ↓

This comment is unneeded, please remove it

> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/media-bus-format.h>
> +
> +#include <video/mipi_display.h>
> +#include <video/of_videomode.h>
> +#include <video/videomode.h>
> +
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_panel.h>
> +
> +static const struct fann_panel_info fann_c3004_panel_info;

Please use fannal everywhere instead of fann

> +
> +struct fann_panel_info {
> +	const struct drm_display_mode *display_mode;
> +	u32 num_of_dsi_lanes;
> +	u32 mipi_dsi_format;
> +	u32 mipi_dsi_mode_flags;
> +	u32 bus_flags;
> +	u32 video_mode;
> +	void (*panel_enable_function)(struct mipi_dsi_device *dsi);
> +};
> +
> +struct fann_panel_data {
> +	const struct fann_panel_info *panel_info;
> +	struct drm_panel panel;
> +	struct gpio_desc *reset;
> +};
> +
> +static struct fann_panel_data *
> +get_fann_panel_data_from_panel(struct drm_panel *panel)
> +{
> +	return container_of(panel, struct fann_panel_data, panel);
> +}
> +
> +static const struct fann_panel_info *
> +get_fann_panel_info_from_panel(struct drm_panel *panel)
> +{
> +	return get_fann_panel_data_from_panel(panel)->panel_info;
> +}
> +
> +enum FANN_VIDEO_MODES_ENUM {
> +	FANN_BURST,
> +	FANN_SYNC_EVENT,
> +	FANN_SYNC_PULSE,
> +	FANN_COMMAND,
> +};
> +
> +static const u32 FANN_VIDEO_MODES[] = {
> +	MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_VIDEO, //BURST
> +	MIPI_DSI_MODE_VIDEO, //SYNC_EVENT
> +	MIPI_DSI_MODE_VIDEO_SYNC_PULSE | MIPI_DSI_MODE_VIDEO, //SYNC_PULSE
> +	MIPI_DSI_CLOCK_NON_CONTINUOUS | MIPI_DSI_MODE_VSYNC_FLUSH //COMMAND MODE
> +};

Do not use this, please use "MIPI_DSI_MODE_VIDEO_SYNC_PULSE | MIPI_DSI_MODE_VIDEO" directly instead
of this table and enums.

> +
> +//macro for writing to DSI
> +#define WRITE_DSI(dsi, seq...)                                                   \
> +	{                                                                        \
> +		const u8 d[] = { seq };                                          \
> +		int ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d));         \
> +		if (ret < 0) {                                                   \
> +			dev_err(&dsi->dev,                                       \
> +				"Error (%d) occurred while trying to"            \
> +				" write MIPI DSI command: %s (decimal value)\n", \
> +				ret, d);                                         \
> +		}                                                                \
> +	}

Please use mipi_dsi_generic_write_seq() instead of this macro.

> +
> +// ↑ include headers, static values, static functions ↑
> +// ↓ INTERACTION whole section: panel specific values, add panel as is shown ↓

Remove all those comments

> +
> +/**
> + * @brief Adding new panel
> + * Includes but isn't limited to following steps:
> + * 1. define new `fann__yourpanel_display_mode` with correct timings
> + * 2. define new `fann_panel_yourpanel_enable_function`
> + * 3. glue everything with fann_yourpanel_panel_info and set that srtucts values
> + * 4. add .compatible = "you,yourpanel", .data = &fann_yourpanel_panel_info }
> + */
> +
> +static const u32 fann_bus_formats[] = {
> +	MEDIA_BUS_FMT_RGB888_1X24,
> +};
> +
> +// resolution 480p x 800p, 56mmx93mm
> +static const struct drm_display_mode fann_c3004_display_mode = {
> +	.clock = 27000,
> +	.hdisplay = 480, // display height pixels
> +	.hsync_start = 480 + 30, // hdisplay + HBP
> +	.hsync_end = 480 + 30 + 8, // hdisplay + HBP + HSync
> +	.htotal = 480 + 30 + 8 + 30, // hdisplay + HBP + HSync + HFP
> +	.vdisplay = 800, // display width pixels
> +	.vsync_start = 800 + 20, // vdisplay + VBP
> +	.vsync_end = 800 + 20 + 8, // vdisplay + VBP + VSync
> +	.vtotal = 800 + 20 + 8 + 20, // vdisplay + VBP + VSync + VFP
> +	.width_mm = 93,
> +	.height_mm = 56,
> +	.flags = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED,
> +};
> +
> +static void fann_panel_fannal_c3004_enable_function(struct mipi_dsi_device *dsi)
> +{
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x13);
> +	WRITE_DSI(dsi, 0xEF, 0x08);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x10);
> +	WRITE_DSI(dsi, 0xC0, 0x63, 0x00);
> +	WRITE_DSI(dsi, 0xC1, 0x0A, 0x0C);
> +	WRITE_DSI(dsi, 0xC2, 0x31, 0x08);
> +	WRITE_DSI(dsi, 0xCC, 0x18);
> +
> +	WRITE_DSI(dsi, 0xB0, 0x00, 0x08, 0x10, 0x0E, 0x11, 0x07, 0x08, 0x08,
> +		  0x08, 0x25, 0x04, 0x12, 0x0F, 0x2C, 0x30, 0x1F);
> +	WRITE_DSI(dsi, 0xB1, 0x00, 0x11, 0x18, 0x0C, 0x10, 0x05, 0x07, 0x09,
> +		  0x08, 0x24, 0x04, 0x11, 0x10, 0x2B, 0x30, 0x1F);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x11);
> +	WRITE_DSI(dsi, 0xB0, 0x4D);
> +	WRITE_DSI(dsi, 0xB1, 0x39);
> +	WRITE_DSI(dsi, 0xB2, 0x87);
> +	WRITE_DSI(dsi, 0xB3, 0x80);
> +	WRITE_DSI(dsi, 0xB5, 0x47);
> +	WRITE_DSI(dsi, 0xB7, 0x8A);
> +	WRITE_DSI(dsi, 0xB8, 0x20);
> +	WRITE_DSI(dsi, 0xB9, 0x10, 0x13);
> +	WRITE_DSI(dsi, 0xC1, 0x78);
> +	WRITE_DSI(dsi, 0xC2, 0x78);
> +	WRITE_DSI(dsi, 0xD0, 0x88);
> +
> +	//PANEL
> +	WRITE_DSI(dsi, 0xE0, 0x00, 0x00, 0x02);
> +	WRITE_DSI(dsi, 0xE1, 0x04, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00,
> +		  0x00, 0x20, 0x20);
> +	WRITE_DSI(dsi, 0xE2, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
> +		  0x00, 0x00, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0xE3, 0x00, 0x00, 0x33, 0x00);
> +	WRITE_DSI(dsi, 0xE4, 0x22, 0x00);
> +	WRITE_DSI(dsi, 0xE5, 0x04, 0x34, 0xAA, 0xAA, 0x06, 0x34, 0xAA, 0xAA,
> +		  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0xE6, 0x00, 0x00, 0x33, 0x00);
> +	WRITE_DSI(dsi, 0xE7, 0x22, 0x00);
> +	WRITE_DSI(dsi, 0xE8, 0x05, 0x34, 0xAA, 0xAA, 0x07, 0x34, 0xAA, 0xAA,
> +		  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0xEB, 0x02, 0x00, 0x40, 0x40, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0xEC, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0xED, 0xFA, 0x45, 0x0B, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
> +		  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xB0, 0x54, 0xAF);
> +	WRITE_DSI(dsi, 0xEF, 0x10, 0x0D, 0x04, 0x08, 0x3F, 0x1F);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x13);
> +	WRITE_DSI(dsi, 0xE8, 0x00, 0x0E);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0x11); //MIPI_DCS_EXIT_SLEEP_MODE
> +
> +	msleep(600);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x13);
> +	WRITE_DSI(dsi, 0xE8, 0x00, 0x0C);
> +	msleep(50);
> +	WRITE_DSI(dsi, 0xE8, 0x00, 0x00);
> +
> +	WRITE_DSI(dsi, 0xFF, 0x77, 0x01, 0x00, 0x00, 0x00);
> +	WRITE_DSI(dsi, 0x29); //MIPI_DCS_SET_DISPLAY_ON
> +	msleep(100);
> +}
> +
> +static const struct fann_panel_info fann_c3004_panel_info = {
> +	.display_mode = &fann_c3004_display_mode,
> +	.num_of_dsi_lanes = 2, //how many wires are connected to the panel
> +	.video_mode = FANN_VIDEO_MODES[FANN_SYNC_PULSE],
> +	.mipi_dsi_format = MIPI_DSI_FMT_RGB888,
> +	.mipi_dsi_mode_flags =
> +		MIPI_DSI_CLOCK_NON_CONTINUOUS | MIPI_DSI_MODE_VSYNC_FLUSH |
> +		MIPI_DSI_MODE_VIDEO_HSE | MIPI_DSI_MODE_NO_EOT_PACKET,
> +	.bus_flags = DRM_BUS_FLAG_DE_LOW | DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
> +	.panel_enable_function = &fann_panel_fannal_c3004_enable_function
> +};

If you handle a single panel, this isn't necessary and you should set all those
values into probe and panel ops

> +
> +// ↑ INTERACTION: panel specific values, add panel as is show in the example ↑
> +// ↓ remove driver/cleanup ↓
> +static void fann_panel_remove(struct mipi_dsi_device *dsi)
> +{
> +	struct fann_panel_data *panel_data = mipi_dsi_get_drvdata(dsi);
> +	struct device *dev = &dsi->dev;
> +	int ret;
> +
> +	ret = mipi_dsi_detach(dsi);
> +	if (ret)
> +		dev_err(dev, "error: disable: mipi detach (%d)\n", ret);
> +
> +	drm_panel_remove(&panel_data->panel);
> +}
> +
> +static int fann_panel_disable(struct drm_panel *panel)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(panel->dev);
> +	struct device *dev = panel->dev;
> +	int ret;
> +
> +	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> +	ret = mipi_dsi_dcs_set_display_off(dsi);
> +	if (ret < 0) {
> +		dev_err(dev, "error: disable: turn display OFF (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	usleep_range(5000, 10000);
> +
> +	ret = mipi_dsi_dcs_enter_sleep_mode(dsi);
> +	if (ret < 0) {
> +		dev_err(dev, "error: disable: enter sleep mode (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fann_panel_unprepare(struct drm_panel *panel)
> +{
> +	struct fann_panel_data *panel_data =
> +		get_fann_panel_data_from_panel(panel);
> +
> +	if (panel_data->reset) {
> +		gpiod_set_value_cansleep(panel_data->reset, 1);
> +		usleep_range(15000, 17000);
> +		gpiod_set_value_cansleep(panel_data->reset, 0);
> +	}
> +
> +	return 0;
> +}
> +
> +static void fann_panel_shutdown(struct mipi_dsi_device *dsi)
> +{
> +	struct fann_panel_data *panel_data = mipi_dsi_get_drvdata(dsi);
> +
> +	fann_panel_disable(&panel_data->panel);
> +	fann_panel_unprepare(&panel_data->panel);
> +}
> +
> +// ↑ remove driver/cleanup ↑
> +// ↓ probe/create functions ↓
> +
> +static int fann_panel_get_modes(struct drm_panel *panel,
> +				struct drm_connector *connector)
> +{
> +	struct drm_display_mode *mode;
> +	const struct fann_panel_info *panel_info =
> +		get_fann_panel_info_from_panel(panel);
> +	const struct drm_display_mode *panel_display_mode =
> +		panel_info->display_mode;

Using this panel_display_mode makes it complex for nothing, please
directly use fann_c3004_display_mode here.

> +
> +	mode = drm_mode_duplicate(connector->dev, panel_display_mode);
> +	if (!mode) {
> +		dev_err(panel->dev, "error: get_modes: add drm mode %ux%u@%u\n",
> +			panel_display_mode->hdisplay,
> +			panel_display_mode->vdisplay,
> +			drm_mode_vrefresh(panel_display_mode));
> +		return -ENOMEM;
> +	}
> +
> +	drm_mode_set_name(mode);
> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +	drm_mode_probed_add(connector, mode);
> +
> +	connector->display_info.width_mm = mode->width_mm;
> +	connector->display_info.height_mm = mode->height_mm;
> +	connector->display_info.bus_flags = panel_info->bus_flags;

Set the bus flasg directly here

> +
> +	drm_display_info_set_bus_formats(&connector->display_info,
> +					 fann_bus_formats,
> +					 ARRAY_SIZE(fann_bus_formats)); > +	return 1;
> +}
> +
> +static const struct of_device_id fann_of_match[] = {
> +	{ .compatible = "fannal,c3004", .data = &fann_c3004_panel_info },

Please introduce such data when you'll need to handle multiple panels,
for now it's mostly unnecessary code.

> +	{ /* sentinel */ }
> +};
> +
> +static int fann_panel_enable(struct drm_panel *panel)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(panel->dev);
> +	const struct fann_panel_info *panel_info =
> +		get_fann_panel_info_from_panel(panel);
> +	panel_info->panel_enable_function(dsi);
> +
> +	return 0;
> +}
> +
> +static int fann_panel_prepare(struct drm_panel *panel)
> +{
> +	struct fann_panel_data *panel_data =
> +		get_fann_panel_data_from_panel(panel);
> +
> +	/* At lest 10ms needed between power-on and reset-out as RM specifies */
> +	usleep_range(10000, 12000);
> +
> +	if (panel_data->reset) {
> +		gpiod_set_value_cansleep(panel_data->reset, 0);
> +		/*
> +		 * 50ms delay after reset-out, as per manufacturer initalization
> +		 * sequence.
> +		 */
> +		msleep(50);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct drm_panel_funcs fann_panel_funcs = {
> +	.prepare = fann_panel_prepare,
> +	.unprepare = fann_panel_unprepare,
> +	.enable = fann_panel_enable,
> +	.disable = fann_panel_disable,
> +	.get_modes = fann_panel_get_modes,
> +};
> +
> +static int fann_panel_probe(struct mipi_dsi_device *dsi)
> +{
> +	struct device *dev = &dsi->dev;
> +	const struct of_device_id *of_id = of_match_device(fann_of_match, dev);
> +	const struct fann_panel_info *panel_info = of_id->data;
> +	struct fann_panel_data *panel_data;
> +	int ret;
> +
> +	dev_notice(dev, "probe driver called\n");

Drop those prints.

> +	if (!panel_info) {
> +		dev_err(dev, "error: probe: get panel_data!\n");
> +		return -ENODEV;
> +	}
> +
> +	panel_data = devm_kzalloc(&dsi->dev, sizeof(*panel_data), GFP_KERNEL);
> +
> +	if (!panel_data)
> +		return -ENOMEM;
> +
> +	panel_data->panel_info = panel_info;
> +	panel_data->reset = devm_gpiod_get_optional(
> +		dev, "reset", GPIOD_OUT_LOW | GPIOD_FLAGS_BIT_NONEXCLUSIVE);
> +
> +	if (IS_ERR(panel_data->reset)) {
> +		ret = PTR_ERR(panel_data->reset);
> +		dev_err(dev,
> +			"error: probe: get reset GPIO: (%d) Check the fdt\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	mipi_dsi_set_drvdata(dsi, panel_data);
> +
> +	dsi->format = panel_info->mipi_dsi_format;
> +	dsi->mode_flags = panel_info->mipi_dsi_mode_flags |
> +			  panel_info->video_mode;
> +	dsi->lanes = panel_info->num_of_dsi_lanes;
> +
> +	gpiod_set_value_cansleep(panel_data->reset, 1);
> +
> +	drm_panel_init(&panel_data->panel, dev, &fann_panel_funcs,
> +		       DRM_MODE_CONNECTOR_DSI);
> +	dev_set_drvdata(dev, panel_data);
> +
> +	drm_panel_add(&panel_data->panel);
> +
> +	ret = mipi_dsi_attach(dsi);
> +	if (ret) {
> +		drm_panel_remove(&panel_data->panel);
> +		dev_err(dev, "error: probe fail: can't attach mipi_dsi!\n");
> +	} else
> +		dev_notice(dev, "probe driver success. Good job!\n");
> +
> +	return ret;
> +}
> +
> +// ↑ probe/create functions ↑
> +// ↓ generic driver stuff ↓
> +
> +static struct mipi_dsi_driver fann_panel_driver = {
> +	.driver = {
> +		.name = "panel-fannal-c3004",
> +		.of_match_table = fann_of_match,
> +	},
> +	.probe = fann_panel_probe,
> +	.remove = fann_panel_remove,
> +	.shutdown = fann_panel_shutdown,
> +};
> +
> +module_mipi_dsi_driver(fann_panel_driver);
> +
> +MODULE_AUTHOR("Paulo Pavacic <pavacic.p@...il.com>");
> +MODULE_DESCRIPTION("Fannal C3004 panel driver");
> +MODULE_LICENSE("GPL");
> +MODULE_DEVICE_TABLE(of, fann_of_match);

I understand you want to write a clean panel driver for learning purposes,
but having unnecessary code isn't appreciated in the Linux codebase,
instead make a simple and readble driver with the state-of-the-art architecture
and helpers.


Thanks,
Neil

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