Re: [PATCH] backlight: Delete the OT200 backlight driver

On Fri, Jun 26, 2020 at 12:25:00PM +0200, Linus Walleij wrote:

This driver has no in-kernel users. The device can only be populated by board files since it does not support device tree nor ACPI, and nothing in the kernel creates a device named "ot200-backlight".

This driver has been in the kernel since 2012. If it is used by out-of-tree code that code should have been upstreamed by now, it's been 8 years.

It uses the idiomatic forked GPIO of the CS5535 which combines pin control and GPIO into its private custom interface, which causes me a headache because that is not how we do things these days: we creates separate pin control and GPIO drivers.

Delete this unused driver.

Cc: Christian Gmeiner christian.gmeiner@gmail.com Signed-off-by: Linus Walleij linus.walleij@linaro.org

I was curious about this if only because this a driver for an x86 system and I wondered how the platform device could ever have been registered.

However I drew a total blank... I can find some tweaks to coreboot that make this code work better[1] but even after a careful search of the coreboot code (just in case some driver I don't know about managed to fetch the "ot200-backlight" string from the firmware) but I can't find any code within reach of a search engine (out of tree of not) that could cause this driver to activate :-(

So, unless we get objections, I've reached the same view as Linus (and in this post have documented the effort involved): Reviewed-by: Daniel Thompson daniel.thompson@linaro.org

Daniel.

[1] https://review.coreboot.org/cgit/coreboot.git/commit/?id=4412bc4

---

drivers/video/backlight/Kconfig | 7 -- drivers/video/backlight/Makefile | 1 - drivers/video/backlight/ot200_bl.c | 162 ----------------------------- 3 files changed, 170 deletions(-) delete mode 100644 drivers/video/backlight/ot200_bl.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig index 7d22d7377606..95c546cc8774 100644 --- a/drivers/video/backlight/Kconfig +++ b/drivers/video/backlight/Kconfig @@ -386,13 +386,6 @@ config BACKLIGHT_LP8788 help This supports TI LP8788 backlight driver.

-config BACKLIGHT_OT200

• tristate "Backlight driver for ot200 visualisation device"
• depends on CS5535_MFGPT && GPIO_CS5535
• help

•  To compile this driver as a module, choose M here: the module will be
  

•  called ot200_bl.
  

config BACKLIGHT_PANDORA tristate "Backlight driver for Pandora console" depends on TWL4030_CORE diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile index 0c1a1524627a..2072d21b60f7 100644 --- a/drivers/video/backlight/Makefile +++ b/drivers/video/backlight/Makefile @@ -45,7 +45,6 @@ obj-$(CONFIG_BACKLIGHT_LP8788) += lp8788_bl.o obj-$(CONFIG_BACKLIGHT_LV5207LP) += lv5207lp.o obj-$(CONFIG_BACKLIGHT_MAX8925) += max8925_bl.o obj-$(CONFIG_BACKLIGHT_OMAP1) += omap1_bl.o -obj-$(CONFIG_BACKLIGHT_OT200) += ot200_bl.o obj-$(CONFIG_BACKLIGHT_PANDORA) += pandora_bl.o obj-$(CONFIG_BACKLIGHT_PCF50633) += pcf50633-backlight.o obj-$(CONFIG_BACKLIGHT_PWM) += pwm_bl.o diff --git a/drivers/video/backlight/ot200_bl.c b/drivers/video/backlight/ot200_bl.c deleted file mode 100644 index 23ee7106c72a..000000000000 --- a/drivers/video/backlight/ot200_bl.c +++ /dev/null @@ -1,162 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0-only -/*

• • Copyright (C) 2012 Bachmann electronic GmbH
• • Christian Gmeiner christian.gmeiner@gmail.com
• • Backlight driver for ot200 visualisation device from
• • Bachmann electronic GmbH.
• */

-#include <linux/module.h> -#include <linux/fb.h> -#include <linux/backlight.h> -#include <linux/gpio.h> -#include <linux/platform_device.h> -#include <linux/cs5535.h>

-static struct cs5535_mfgpt_timer *pwm_timer;

-/* this array defines the mapping of brightness in % to pwm frequency */ -static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,

• 		  2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
  

• 		  4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
  

• 		  10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
  

• 		  17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
  

• 		  30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
  

• 		  53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
  

• 		  93, 97, 103, 108, 114, 120, 126, 133, 140,
  

• 		  147, 155, 163};
  

-struct ot200_backlight_data {

• int current_brightness;

-};

-#define GPIO_DIMM 27 -#define SCALE 1 -#define CMP1MODE 0x2 /* compare on GE; output high on compare

• 		 * greater than or equal */
  

-#define PWM_SETUP (SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN) -#define MAX_COMP2 163

-static int ot200_backlight_update_status(struct backlight_device *bl) -{

• struct ot200_backlight_data *data = bl_get_data(bl);
• int brightness = bl->props.brightness;
• if (bl->props.state & BL_CORE_FBBLANK)

• brightness = 0;
  

• /* enable or disable PWM timer */
• if (brightness == 0)

• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
  

• else if (data->current_brightness == 0) {

• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
  

• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
  

• 	MFGPT_SETUP_CNTEN);
  

• }
• /* apply new brightness value */
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,

• MAX_COMP2 - dim_table[brightness]);
  

• data->current_brightness = brightness;
• return 0;

-}

-static int ot200_backlight_get_brightness(struct backlight_device *bl) -{

• struct ot200_backlight_data *data = bl_get_data(bl);
• return data->current_brightness;

-}

-static const struct backlight_ops ot200_backlight_ops = {

• .update_status = ot200_backlight_update_status,
• .get_brightness = ot200_backlight_get_brightness,

-};

-static int ot200_backlight_probe(struct platform_device *pdev) -{

• struct backlight_device *bl;
• struct ot200_backlight_data *data;
• struct backlight_properties props;
• int retval = 0;
• /* request gpio */
• if (devm_gpio_request(&pdev->dev, GPIO_DIMM,

• 		"ot200 backlight dimmer") < 0) {
  

• dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
  

• return -ENODEV;
  

• }
• /* request timer */
• pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
• if (!pwm_timer) {

• dev_err(&pdev->dev, "MFGPT 7 not available\n");
  

• return -ENODEV;
  

• }
• data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
• if (!data) {

• retval = -ENOMEM;
  

• goto error_devm_kzalloc;
  

• }
• /* setup gpio */
• cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
• cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);
• /* setup timer */
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);
• data->current_brightness = 100;
• props.max_brightness = 100;
• props.brightness = 100;
• props.type = BACKLIGHT_RAW;
• bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),

• 			&pdev->dev, data, &ot200_backlight_ops,
  

• 			&props);
  

• if (IS_ERR(bl)) {

• dev_err(&pdev->dev, "failed to register backlight\n");
  

• retval = PTR_ERR(bl);
  

• goto error_devm_kzalloc;
  

• }
• platform_set_drvdata(pdev, bl);
• return 0;

-error_devm_kzalloc:

• cs5535_mfgpt_free_timer(pwm_timer);
• return retval;

-}

-static int ot200_backlight_remove(struct platform_device *pdev) -{

• /* on module unload set brightness to 100% */
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
• cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,

• MAX_COMP2 - dim_table[100]);
  

• cs5535_mfgpt_free_timer(pwm_timer);
• return 0;

-}

-static struct platform_driver ot200_backlight_driver = {

• .driver = {

• .name	= "ot200-backlight",
  

• },
• .probe = ot200_backlight_probe,
• .remove = ot200_backlight_remove,

-};

-module_platform_driver(ot200_backlight_driver);

-MODULE_DESCRIPTION("backlight driver for ot200 visualisation device"); -MODULE_AUTHOR("Christian Gmeiner christian.gmeiner@gmail.com"); -MODULE_LICENSE("GPL");

-MODULE_ALIAS("platform:ot200-backlight");

2.25.4