Re: [PATCH v1 07/11] media: Add registration helpers for V4L2 flash sub-devices

[Sakari Ailus <sakari.ailus@iki.fi>]

Hi Jacek,

On Mon, Mar 23, 2015 at 04:08:10PM +0100, Jacek Anaszewski wrote:
> Hi Sakari,
> 
> Thanks for the review.
> 
> On 03/22/2015 01:22 AM, Sakari Ailus wrote:
> >Hi Jacek,
> >
> >Thanks for the updated set. Some comments below.
> >
> >On Fri, Mar 20, 2015 at 04:03:27PM +0100, Jacek Anaszewski wrote:
> >>This patch adds helper functions for registering/unregistering
> >>LED Flash class devices as V4L2 sub-devices. The functions should
> >>be called from the LED subsystem device driver. In case the
> >>support for V4L2 Flash sub-devices is disabled in the kernel
> >>config the functions' empty versions will be used.
> >>
> >>Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
> >>Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> >>Cc: Sakari Ailus <sakari.ailus@iki.fi>
> >>Cc: Hans Verkuil <hans.verkuil@cisco.com>
> >>---
> >>  drivers/media/v4l2-core/Kconfig      |   12 +
> >>  drivers/media/v4l2-core/Makefile     |    2 +
> >>  drivers/media/v4l2-core/v4l2-flash.c |  607 ++++++++++++++++++++++++++++++++++
> >>  include/media/v4l2-flash.h           |  145 ++++++++
> >>  4 files changed, 766 insertions(+)
> >>  create mode 100644 drivers/media/v4l2-core/v4l2-flash.c
> >>  create mode 100644 include/media/v4l2-flash.h
> >>
> >>diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
> >>index ba7e21a..0659598 100644
> >>--- a/drivers/media/v4l2-core/Kconfig
> >>+++ b/drivers/media/v4l2-core/Kconfig
> >>@@ -44,6 +44,18 @@ config V4L2_MEM2MEM_DEV
> >>          tristate
> >>          depends on VIDEOBUF2_CORE
> >>
> >>+# Used by LED subsystem flash drivers
> >>+config V4L2_FLASH_LED_CLASS
> >>+	tristate "Enable support for Flash sub-devices"
> >>+	depends on VIDEO_V4L2_SUBDEV_API
> >>+	depends on LEDS_CLASS_FLASH
> >>+	depends on OF
> >
> >I think you can drop OF dependency. A no-op implementation will be used if
> >it's disabled.
> 
> The sub-devices are matched by a sub-LED's device_node. This is the only
> way of matching the v4l2-flash sub-devs. Without OF a v4l2-flash
> sub-device will not get registered at all.

Not all systems use OF, and for those there are different async sub-device
matching options such as i2c or device name. A sub-device driver should not
mandate using a particular one.

> What do you mean by "no-op implementation"?

There are variants of most of_*() functions that do nothing. These variants
are used if CONFIG_OF is disabled, so the drivers won't need lots of ugly
#ifdefs.

> >>+	---help---
> >>+	  Say Y here to enable support for Flash sub-devices, which allow
> >>+	  to control LED class devices with use of V4L2 Flash controls.
> >>+
> >>+	  When in doubt, say N.
> >>+
> >>  # Used by drivers that need Videobuf modules
> >>  config VIDEOBUF_GEN
> >>  	tristate
> >>diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> >>index 63d29f2..44e858c 100644
> >>--- a/drivers/media/v4l2-core/Makefile
> >>+++ b/drivers/media/v4l2-core/Makefile
> >>@@ -22,6 +22,8 @@ obj-$(CONFIG_VIDEO_TUNER) += tuner.o
> >>
> >>  obj-$(CONFIG_V4L2_MEM2MEM_DEV) += v4l2-mem2mem.o
> >>
> >>+obj-$(CONFIG_V4L2_FLASH_LED_CLASS) += v4l2-flash.o
> >>+
> >>  obj-$(CONFIG_VIDEOBUF_GEN) += videobuf-core.o
> >>  obj-$(CONFIG_VIDEOBUF_DMA_SG) += videobuf-dma-sg.o
> >>  obj-$(CONFIG_VIDEOBUF_DMA_CONTIG) += videobuf-dma-contig.o
> >>diff --git a/drivers/media/v4l2-core/v4l2-flash.c b/drivers/media/v4l2-core/v4l2-flash.c
> >>new file mode 100644
> >>index 0000000..804c2e4
> >>--- /dev/null
> >>+++ b/drivers/media/v4l2-core/v4l2-flash.c
> >>@@ -0,0 +1,607 @@
> >>+/*
> >>+ * V4L2 Flash LED sub-device registration helpers.
> >>+ *
> >>+ *	Copyright (C) 2015 Samsung Electronics Co., Ltd
> >>+ *	Author: Jacek Anaszewski <j.anaszewski@samsung.com>
> >>+ *
> >>+ * This program is free software; you can redistribute it and/or modify
> >>+ * it under the terms of the GNU General Public License version 2 as
> >>+ * published by the Free Software Foundation.
> >>+ */
> >>+
> >>+#include <linux/led-class-flash.h>
> >>+#include <linux/module.h>
> >>+#include <linux/mutex.h>
> >>+#include <linux/of.h>
> >>+#include <linux/slab.h>
> >>+#include <linux/types.h>
> >>+#include <media/v4l2-flash.h>
> >>+#include "../../leds/leds.h"
> >
> >What do you need from leds.h? Shouldn't this be e.g. under include/linux
> >instead?
> >
> >>+#define has_flash_op(v4l2_flash, op)				\
> >>+	(v4l2_flash && v4l2_flash->ops->op)
> >>+
> >>+#define call_flash_op(v4l2_flash, op, arg)			\
> >>+		(has_flash_op(v4l2_flash, op) ?			\
> >>+			v4l2_flash->ops->op(v4l2_flash, arg) :	\
> >>+			-EINVAL)
> >>+
> >>+static enum led_brightness __intensity_to_led_brightness(
> >>+					struct v4l2_ctrl *ctrl,
> >>+					s32 intensity)
> >>+{
> >>+	s64 intensity64 = intensity - ctrl->minimum;
> >>+
> >>+	do_div(intensity64, ctrl->step);
> >>+
> >>+	/*
> >>+	 * Indicator LEDs, unlike torch LEDs, are turned on/off basing on
> >>+	 * the state of V4L2_CID_FLASH_INDICATOR_INTENSITY control only.
> >>+	 * Therefore it must be possible to set it to 0 level which in
> >>+	 * the LED subsystem reflects LED_OFF state.
> >>+	 */
> >>+	if (ctrl->id != V4L2_CID_FLASH_INDICATOR_INTENSITY)
> >>+		++intensity64;
> >>+
> >>+	return intensity64;
> >>+}
> >>+
> >>+static s32 __led_brightness_to_intensity(struct v4l2_ctrl *ctrl,
> >>+					 enum led_brightness brightness)
> >>+{
> >>+	/*
> >>+	 * Indicator LEDs, unlike torch LEDs, are turned on/off basing on
> >>+	 * the state of V4L2_CID_FLASH_INDICATOR_INTENSITY control only.
> >>+	 * Do not decrement brightness read from the LED subsystem for
> >>+	 * indicator LED as it may equal 0. For torch LEDs this function
> >>+	 * is called only when V4L2_FLASH_LED_MODE_TORCH is set and the
> >>+	 * brightness read is guaranteed to be greater than 0. In the mode
> >>+	 * V4L2_FLASH_LED_MODE_NONE the cached torch intensity value is used.
> >>+	 */
> >>+	if (ctrl->id != V4L2_CID_FLASH_INDICATOR_INTENSITY)
> >>+		--brightness;
> >>+
> >>+	return (brightness * ctrl->step) + ctrl->minimum;
> >>+}
> >>+
> >>+static void v4l2_flash_set_led_brightness(struct v4l2_flash *v4l2_flash,
> >>+					struct v4l2_ctrl *ctrl)
> >>+{
> >>+	struct v4l2_ctrl **ctrls = v4l2_flash->ctrls;
> >>+	enum led_brightness brightness;
> >>+
> >>+	if (has_flash_op(v4l2_flash, intensity_to_led_brightness))
> >>+		brightness = call_flash_op(v4l2_flash,
> >>+					intensity_to_led_brightness,
> >>+					ctrl->val);
> >>+	else
> >>+		brightness = __intensity_to_led_brightness(ctrl, ctrl->val);
> >>+	/*
> >>+	 * In case a LED Flash class driver provides ops for custom
> >>+	 * brightness <-> intensity conversion, it also must have defined
> >>+	 * related v4l2 control step == 1. In such a case a backward conversion
> >>+	 * from led brightness to v4l2 intensity is required to find out the
> >>+	 * the aligned intensity value.
> >>+	 */
> >>+	if (has_flash_op(v4l2_flash, led_brightness_to_intensity))
> >>+		ctrl->val = call_flash_op(v4l2_flash,
> >>+					led_brightness_to_intensity,
> >>+					brightness);
> >>+
> >>+	if (ctrl == ctrls[TORCH_INTENSITY] &&
> >>+	    ctrls[LED_MODE]->val != V4L2_FLASH_LED_MODE_TORCH)
> >>+		return;
> >>+
> >>+	led_set_brightness(&v4l2_flash->fled_cdev->led_cdev, brightness);
> >>+}
> >>+
> >>+static int v4l2_flash_update_led_brightness(struct v4l2_flash *v4l2_flash,
> >>+					struct v4l2_ctrl *ctrl)
> >>+{
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	struct v4l2_ctrl **ctrls = v4l2_flash->ctrls;
> >>+	int ret;
> >>+
> >>+	/*
> >>+	 * Update torch brightness only if in TORCH_MODE. In other modes torch
> >>+	 * led is turned off, which would spuriously inform the user space that
> >>+	 * V4L2_CID_FLASH_TORCH_INTENSITY control value has changed to 0.
> >>+	 */
> >>+	if (ctrl == ctrls[TORCH_INTENSITY] &&
> >>+	    ctrls[LED_MODE]->val != V4L2_FLASH_LED_MODE_TORCH)
> >>+		return 0;
> >>+
> >>+	ret = led_update_brightness(led_cdev);
> >>+	if (ret < 0)
> >>+		return ret;
> >>+
> >>+	if (has_flash_op(v4l2_flash, led_brightness_to_intensity))
> >>+		ctrl->val = call_flash_op(v4l2_flash,
> >>+						led_brightness_to_intensity,
> >>+						led_cdev->brightness);
> >>+	else
> >>+		ctrl->val = __led_brightness_to_intensity(ctrl,
> >>+						led_cdev->brightness);
> >>+
> >>+	return 0;
> >>+}
> >>+
> >>+static int v4l2_flash_g_volatile_ctrl(struct v4l2_ctrl *c)
> >>+{
> >>+	struct v4l2_flash *v4l2_flash = v4l2_ctrl_to_v4l2_flash(c);
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	bool is_strobing;
> >>+	int ret;
> >>+
> >>+	switch (c->id) {
> >>+	case V4L2_CID_FLASH_TORCH_INTENSITY:
> >>+	case V4L2_CID_FLASH_INDICATOR_INTENSITY:
> >>+		return v4l2_flash_update_led_brightness(v4l2_flash, c);
> >>+	case V4L2_CID_FLASH_INTENSITY:
> >>+		ret = led_update_flash_brightness(fled_cdev);
> >>+		if (ret < 0)
> >>+			return ret;
> >>+		/* no conversion is needed */
> >>+		c->val = fled_cdev->brightness.val;
> >>+		return 0;
> >>+	case V4L2_CID_FLASH_STROBE_STATUS:
> >>+		ret = led_get_flash_strobe(fled_cdev, &is_strobing);
> >>+		if (ret < 0)
> >>+			return ret;
> >>+		c->val = is_strobing;
> >>+		return 0;
> >>+	case V4L2_CID_FLASH_FAULT:
> >>+		/* LED faults map directly to V4L2 flash faults */
> >>+		return led_get_flash_fault(fled_cdev, &c->val);
> >>+	default:
> >>+		return -EINVAL;
> >>+	}
> >>+}
> >>+
> >>+static bool __software_strobe_mode_inactive(struct v4l2_ctrl **ctrls)
> >>+{
> >>+	return ((ctrls[LED_MODE]->val != V4L2_FLASH_LED_MODE_FLASH) ||
> >>+		(ctrls[STROBE_SOURCE] && (ctrls[STROBE_SOURCE]->val !=
> >>+				V4L2_FLASH_STROBE_SOURCE_SOFTWARE)));
> >>+}
> >>+
> >>+static int v4l2_flash_s_ctrl(struct v4l2_ctrl *c)
> >>+{
> >>+	struct v4l2_flash *v4l2_flash = v4l2_ctrl_to_v4l2_flash(c);
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	struct v4l2_ctrl **ctrls = v4l2_flash->ctrls;
> >>+	bool external_strobe;
> >>+	int ret = 0;
> >>+
> >>+	switch (c->id) {
> >>+	case V4L2_CID_FLASH_LED_MODE:
> >>+		switch (c->val) {
> >>+		case V4L2_FLASH_LED_MODE_NONE:
> >>+			led_set_brightness(led_cdev, LED_OFF);
> >>+			return led_set_flash_strobe(fled_cdev, false);
> >>+		case V4L2_FLASH_LED_MODE_FLASH:
> >>+			/* Turn the torch LED off */
> >>+			led_set_brightness(led_cdev, LED_OFF);
> >>+			if (ctrls[STROBE_SOURCE]) {
> >>+				external_strobe = (ctrls[STROBE_SOURCE]->val ==
> >>+					V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
> >>+
> >>+				ret = call_flash_op(v4l2_flash,
> >>+						external_strobe_set,
> >>+						external_strobe);
> >>+			}
> >>+			return ret;
> >>+		case V4L2_FLASH_LED_MODE_TORCH:
> >>+			if (ctrls[STROBE_SOURCE]) {
> >>+				ret = call_flash_op(v4l2_flash,
> >>+						external_strobe_set,
> >>+						false);
> >>+				if (ret < 0)
> >>+					return ret;
> >>+			}
> >>+			/* Stop flash strobing */
> >>+			ret = led_set_flash_strobe(fled_cdev, false);
> >>+			if (ret < 0)
> >>+				return ret;
> >>+
> >>+			v4l2_flash_set_led_brightness(v4l2_flash,
> >>+							ctrls[TORCH_INTENSITY]);
> >>+			return 0;
> >>+		}
> >>+		break;
> >>+	case V4L2_CID_FLASH_STROBE_SOURCE:
> >>+		external_strobe = (c->val == V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
> >>+		/*
> >>+		 * For some hardware arrangements setting strobe source may
> >>+		 * affect torch mode. Therefore, if not in the flash mode,
> >>+		 * cache only this setting. It will be applied upon switching
> >>+		 * to flash mode.
> >>+		 */
> >>+		if (ctrls[LED_MODE]->val != V4L2_FLASH_LED_MODE_FLASH)
> >>+			return 0;
> >>+
> >>+		return call_flash_op(v4l2_flash, external_strobe_set,
> >>+					external_strobe);
> >>+	case V4L2_CID_FLASH_STROBE:
> >>+		if (__software_strobe_mode_inactive(ctrls))
> >>+			return -EBUSY;
> >>+		return led_set_flash_strobe(fled_cdev, true);
> >>+	case V4L2_CID_FLASH_STROBE_STOP:
> >>+		if (__software_strobe_mode_inactive(ctrls))
> >>+			return -EBUSY;
> >>+		return led_set_flash_strobe(fled_cdev, false);
> >>+	case V4L2_CID_FLASH_TIMEOUT:
> >>+		/* no conversion is needed */
> >>+		return led_set_flash_timeout(fled_cdev, c->val);
> >>+	case V4L2_CID_FLASH_INTENSITY:
> >>+		/* no conversion is needed */
> >>+		return led_set_flash_brightness(fled_cdev, c->val);
> >>+	case V4L2_CID_FLASH_TORCH_INTENSITY:
> >>+	case V4L2_CID_FLASH_INDICATOR_INTENSITY:
> >>+		v4l2_flash_set_led_brightness(v4l2_flash, c);
> >>+		return 0;
> >>+	}
> >>+
> >>+	return -EINVAL;
> >>+}
> >>+
> >>+static const struct v4l2_ctrl_ops v4l2_flash_ctrl_ops = {
> >>+	.g_volatile_ctrl = v4l2_flash_g_volatile_ctrl,
> >>+	.s_ctrl = v4l2_flash_s_ctrl,
> >>+};
> >>+
> >>+static void fill_ctrl_init_data(struct v4l2_flash *v4l2_flash,
> >>+			  struct v4l2_flash_ctrl_config *flash_ctrl_cfg,
> >>+			  struct v4l2_flash_ctrl_data *ctrl_init_data)
> >>+{
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	const struct led_flash_ops *fled_cdev_ops = fled_cdev->ops;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	struct v4l2_ctrl_config *ctrl_cfg;
> >>+	u32 mask;
> >>+
> >>+	/* Init FLASH_FAULT ctrl data */
> >>+	if (flash_ctrl_cfg->flash_faults) {
> >>+		ctrl_init_data[FLASH_FAULT].cid = V4L2_CID_FLASH_FAULT;
> >>+		ctrl_cfg = &ctrl_init_data[FLASH_FAULT].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_FAULT;
> >>+		ctrl_cfg->max = flash_ctrl_cfg->flash_faults;
> >>+		ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE |
> >>+				  V4L2_CTRL_FLAG_READ_ONLY;
> >>+	}
> >>+
> >>+	/* Init INDICATOR_INTENSITY ctrl data */
> >>+	if (flash_ctrl_cfg->indicator_led) {
> >>+		ctrl_init_data[INDICATOR_INTENSITY].cid =
> >>+					V4L2_CID_FLASH_INDICATOR_INTENSITY;
> >>+		ctrl_init_data[INDICATOR_INTENSITY].config =
> >>+						flash_ctrl_cfg->intensity;
> >>+		ctrl_cfg = &ctrl_init_data[INDICATOR_INTENSITY].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_INDICATOR_INTENSITY;
> >>+		ctrl_cfg->min = 0;
> >>+		ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE;
> >>+
> >>+		/* Indicator LED can have only faults and intensity controls. */
> >>+		return;
> >>+	}
> >>+
> >>+	/* Init FLASH_LED_MODE ctrl data */
> >>+	mask = 1 << V4L2_FLASH_LED_MODE_NONE |
> >>+	       1 << V4L2_FLASH_LED_MODE_TORCH;
> >>+	if (led_cdev->flags & LED_DEV_CAP_FLASH)
> >>+		mask |= 1 << V4L2_FLASH_LED_MODE_FLASH;
> >>+
> >>+	ctrl_init_data[LED_MODE].cid = V4L2_CID_FLASH_LED_MODE;
> >>+	ctrl_cfg = &ctrl_init_data[LED_MODE].config;
> >>+	ctrl_cfg->id = V4L2_CID_FLASH_LED_MODE;
> >>+	ctrl_cfg->max = V4L2_FLASH_LED_MODE_TORCH;
> >>+	ctrl_cfg->menu_skip_mask = ~mask;
> >>+	ctrl_cfg->def = V4L2_FLASH_LED_MODE_NONE;
> >>+	ctrl_cfg->flags = 0;
> >>+
> >>+	/* Init TORCH_INTENSITY ctrl data */
> >>+	ctrl_init_data[TORCH_INTENSITY].cid = V4L2_CID_FLASH_TORCH_INTENSITY;
> >>+	ctrl_init_data[TORCH_INTENSITY].config = flash_ctrl_cfg->intensity;
> >>+	ctrl_cfg = &ctrl_init_data[TORCH_INTENSITY].config;
> >>+	ctrl_cfg->id = V4L2_CID_FLASH_TORCH_INTENSITY;
> >>+	ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE;
> >>+
> >>+	if (!(led_cdev->flags & LED_DEV_CAP_FLASH))
> >>+		return;
> >>+
> >>+	/* Init FLASH_STROBE ctrl data */
> >>+	ctrl_init_data[FLASH_STROBE].cid = V4L2_CID_FLASH_STROBE;
> >>+	ctrl_cfg = &ctrl_init_data[FLASH_STROBE].config;
> >>+	ctrl_cfg->id = V4L2_CID_FLASH_STROBE;
> >>+
> >>+	/* Init STROBE_STOP ctrl data */
> >>+	ctrl_init_data[STROBE_STOP].cid = V4L2_CID_FLASH_STROBE_STOP;
> >>+	ctrl_cfg = &ctrl_init_data[STROBE_STOP].config;
> >>+	ctrl_cfg->id = V4L2_CID_FLASH_STROBE_STOP;
> >>+
> >>+	/* Init FLASH_STROBE_SOURCE ctrl data */
> >>+	if (flash_ctrl_cfg->has_external_strobe) {
> >>+		mask = (1 << V4L2_FLASH_STROBE_SOURCE_SOFTWARE) |
> >>+		       (1 << V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
> >>+		ctrl_init_data[STROBE_SOURCE].cid =
> >>+					V4L2_CID_FLASH_STROBE_SOURCE;
> >>+		ctrl_cfg = &ctrl_init_data[STROBE_SOURCE].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_STROBE_SOURCE;
> >>+		ctrl_cfg->max = V4L2_FLASH_STROBE_SOURCE_EXTERNAL;
> >>+		ctrl_cfg->menu_skip_mask = ~mask;
> >>+		ctrl_cfg->def = V4L2_FLASH_STROBE_SOURCE_SOFTWARE;
> >>+	}
> >>+
> >>+	/* Init STROBE_STATUS ctrl data */
> >>+	if (fled_cdev_ops->strobe_get) {
> >>+		ctrl_init_data[STROBE_STATUS].cid =
> >>+					V4L2_CID_FLASH_STROBE_STATUS;
> >>+		ctrl_cfg = &ctrl_init_data[STROBE_STATUS].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_STROBE_STATUS;
> >>+		ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE |
> >>+				  V4L2_CTRL_FLAG_READ_ONLY;
> >>+	}
> >>+
> >>+	/* Init FLASH_TIMEOUT ctrl data */
> >>+	if (fled_cdev_ops->timeout_set) {
> >>+		ctrl_init_data[FLASH_TIMEOUT].cid = V4L2_CID_FLASH_TIMEOUT;
> >>+		ctrl_init_data[FLASH_TIMEOUT].config =
> >>+					flash_ctrl_cfg->flash_timeout;
> >>+		ctrl_cfg = &ctrl_init_data[FLASH_TIMEOUT].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_TIMEOUT;
> >>+	}
> >>+
> >>+	/* Init FLASH_INTENSITY ctrl data */
> >>+	if (fled_cdev_ops->flash_brightness_set) {
> >>+		ctrl_init_data[FLASH_INTENSITY].cid = V4L2_CID_FLASH_INTENSITY;
> >>+		ctrl_init_data[FLASH_INTENSITY].config =
> >>+					flash_ctrl_cfg->flash_intensity;
> >>+		ctrl_cfg = &ctrl_init_data[FLASH_INTENSITY].config;
> >>+		ctrl_cfg->id = V4L2_CID_FLASH_INTENSITY;
> >>+		ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE;
> >>+	}
> >>+}
> >>+
> >>+static int v4l2_flash_init_controls(struct v4l2_flash *v4l2_flash,
> >>+				struct v4l2_flash_ctrl_config *flash_ctrl_cfg)
> >>+
> >>+{
> >>+	struct v4l2_flash_ctrl_data *ctrl_init_data;
> >>+	struct v4l2_ctrl *ctrl;
> >>+	struct v4l2_ctrl_config *ctrl_cfg;
> >>+	int i, ret, num_ctrls = 0;
> >>+
> >>+	/* allocate memory dynamically so as not to exceed stack frame size */
> >>+	ctrl_init_data = kcalloc(NUM_FLASH_CTRLS, sizeof(*ctrl_init_data),
> >>+					GFP_KERNEL);
> >>+	if (!ctrl_init_data)
> >>+		return -ENOMEM;
> >>+
> >>+	fill_ctrl_init_data(v4l2_flash, flash_ctrl_cfg, ctrl_init_data);
> >>+
> >>+	for (i = 0; i < NUM_FLASH_CTRLS; ++i)
> >>+		if (ctrl_init_data[i].cid)
> >>+			++num_ctrls;
> >>+
> >>+	v4l2_ctrl_handler_init(&v4l2_flash->hdl, num_ctrls);
> >>+
> >>+	for (i = 0; i < NUM_FLASH_CTRLS; ++i) {
> >>+		ctrl_cfg = &ctrl_init_data[i].config;
> >>+		if (!ctrl_init_data[i].cid)
> >>+			continue;
> >>+
> >>+		if (ctrl_cfg->id == V4L2_CID_FLASH_LED_MODE ||
> >>+		    ctrl_cfg->id == V4L2_CID_FLASH_STROBE_SOURCE)
> >>+			ctrl = v4l2_ctrl_new_std_menu(&v4l2_flash->hdl,
> >>+						&v4l2_flash_ctrl_ops,
> >>+						ctrl_cfg->id,
> >>+						ctrl_cfg->max,
> >>+						ctrl_cfg->menu_skip_mask,
> >>+						ctrl_cfg->def);
> >>+		else
> >>+			ctrl = v4l2_ctrl_new_std(&v4l2_flash->hdl,
> >>+						&v4l2_flash_ctrl_ops,
> >>+						ctrl_cfg->id,
> >>+						ctrl_cfg->min,
> >>+						ctrl_cfg->max,
> >>+						ctrl_cfg->step,
> >>+						ctrl_cfg->def);
> >>+
> >>+		if (ctrl)
> >>+			ctrl->flags |= ctrl_cfg->flags;
> >>+
> >>+		if (i <= STROBE_SOURCE)
> >>+			v4l2_flash->ctrls[i] = ctrl;
> >>+	}
> >>+
> >>+	kfree(ctrl_init_data);
> >>+
> >>+	if (v4l2_flash->hdl.error) {
> >>+		ret = v4l2_flash->hdl.error;
> >>+		goto error_free_handler;
> >>+	}
> >>+
> >>+	v4l2_ctrl_handler_setup(&v4l2_flash->hdl);
> >>+
> >>+	v4l2_flash->sd.ctrl_handler = &v4l2_flash->hdl;
> >>+
> >>+	return 0;
> >>+
> >>+error_free_handler:
> >>+	v4l2_ctrl_handler_free(&v4l2_flash->hdl);
> >>+	return ret;
> >>+}
> >>+
> >>+static int __sync_device_with_v4l2_controls(struct v4l2_flash *v4l2_flash)
> >>+{
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	struct v4l2_ctrl **ctrls = v4l2_flash->ctrls;
> >>+	int ret = 0;
> >>+
> >>+	if (ctrls[FLASH_TIMEOUT]) {
> >>+		ret = led_set_flash_timeout(fled_cdev,
> >>+					ctrls[FLASH_TIMEOUT]->val);
> >>+		if (ret < 0)
> >>+			return ret;
> >>+	}
> >>+
> >>+	if (ctrls[FLASH_INTENSITY]) {
> >>+		ret = led_set_flash_brightness(fled_cdev,
> >>+					ctrls[FLASH_INTENSITY]->val);
> >>+		if (ret < 0)
> >>+			return ret;
> >>+	}
> >>+
> >>+	/*
> >>+	 * For some hardware arrangements setting strobe source may affect
> >>+	 * torch mode. Synchronize strobe source setting only if not in torch
> >>+	 * mode. For torch mode case it will get synchronized upon switching
> >>+	 * to flash mode.
> >>+	 */
> >>+	if (ctrls[STROBE_SOURCE] &&
> >>+	    ctrls[LED_MODE]->val != V4L2_FLASH_LED_MODE_TORCH)
> >>+		ret = call_flash_op(v4l2_flash, external_strobe_set,
> >>+					ctrls[STROBE_SOURCE]->val);
> >>+
> >>+	if (ctrls[INDICATOR_INTENSITY])
> >>+		v4l2_flash_set_led_brightness(v4l2_flash,
> >>+						ctrls[INDICATOR_INTENSITY]);
> >>+	else
> >>+		v4l2_flash_set_led_brightness(v4l2_flash,
> >>+						ctrls[TORCH_INTENSITY]);
> >>+
> >>+	return ret;
> >>+}
> >>+
> >>+/*
> >>+ * V4L2 subdev internal operations
> >>+ */
> >>+
> >>+static int v4l2_flash_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> >>+{
> >>+	struct v4l2_flash *v4l2_flash = v4l2_subdev_to_v4l2_flash(sd);
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	int ret = 0;
> >
> >No need to initialise ret.
> >
> >>+
> >>+	mutex_lock(&led_cdev->led_access);
> >>+
> >>+	if (!v4l2_fh_is_singular(&fh->vfh)) {
> >
> >I'm not sure about this --- no current flash driver AFAIK provides exclusive
> >access.
> 
> v4l2_flash_open has a side effect in the form of writing device
> registers with v4l2-flash controls state. Generally it should not
> affect e.g. the flash strobe if it took place in the same moment.
> 
> What should be added, if we are to allow multiple users, is the
> reference counter to be able to detect that last user is closing
> a sub-dev and only then set the strobe source to software.

You shouldn't need a counter, just use v4l2_if_is_singular() as you already
do. But instead of returning -EBUSY, return 0. :-)

> >>+		ret = -EBUSY;
> >>+		goto unlock;
> >>+	}
> >>+
> >>+	led_sysfs_disable(led_cdev);
> >>+	led_trigger_remove(led_cdev);
> >>+
> >>+	ret = __sync_device_with_v4l2_controls(v4l2_flash);
> >>+
> >>+unlock:
> >>+	mutex_unlock(&led_cdev->led_access);
> >>+	return ret;
> >>+}
> >>+
> >>+static int v4l2_flash_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> >>+{
> >>+	struct v4l2_flash *v4l2_flash = v4l2_subdev_to_v4l2_flash(sd);
> >>+	struct led_classdev_flash *fled_cdev = v4l2_flash->fled_cdev;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	int ret = 0;
> >
> >ret is redundant.
> 
> I think that I forgot to assign the v4l2_ctrl_s_ctrl result to it.
> 
> >>+
> >>+	mutex_lock(&led_cdev->led_access);
> >>+
> >>+	if (v4l2_flash->ctrls[STROBE_SOURCE])
> >>+		v4l2_ctrl_s_ctrl(v4l2_flash->ctrls[STROBE_SOURCE],
> >>+				V4L2_FLASH_STROBE_SOURCE_SOFTWARE);
> >>+
> >>+	led_sysfs_enable(led_cdev);
> >>+
> >>+	mutex_unlock(&led_cdev->led_access);
> >>+
> >>+	return ret;
> >>+}
> >>+
> >>+static const struct v4l2_subdev_internal_ops v4l2_flash_subdev_internal_ops = {
> >>+	.open = v4l2_flash_open,
> >>+	.close = v4l2_flash_close,
> >>+};
> >>+
> >>+static const struct v4l2_subdev_core_ops v4l2_flash_core_ops = {
> >>+	.queryctrl = v4l2_subdev_queryctrl,
> >>+	.querymenu = v4l2_subdev_querymenu,
> >>+};
> >>+
> >>+static const struct v4l2_subdev_ops v4l2_flash_subdev_ops = {
> >>+	.core = &v4l2_flash_core_ops,
> >>+};
> >>+
> >>+struct v4l2_flash *v4l2_flash_init(struct led_classdev_flash *fled_cdev,
> >>+				   const struct v4l2_flash_ops *ops,
> >>+				   struct v4l2_flash_ctrl_config *config)
> >>+{
> >>+	struct v4l2_flash *v4l2_flash;
> >>+	struct led_classdev *led_cdev = &fled_cdev->led_cdev;
> >>+	struct v4l2_subdev *sd;
> >>+	int ret;
> >>+
> >>+	if (!fled_cdev || !ops || !config)
> >>+		return ERR_PTR(-EINVAL);
> >>+
> >>+	v4l2_flash = devm_kzalloc(led_cdev->dev, sizeof(*v4l2_flash),
> >>+					GFP_KERNEL);
> >>+	if (!v4l2_flash)
> >>+		return ERR_PTR(-ENOMEM);
> >>+
> >>+	sd = &v4l2_flash->sd;
> >>+	v4l2_flash->fled_cdev = fled_cdev;
> >>+	v4l2_flash->ops = ops;
> >>+	sd->dev = led_cdev->dev;
> >>+	v4l2_subdev_init(sd, &v4l2_flash_subdev_ops);
> >>+	sd->internal_ops = &v4l2_flash_subdev_internal_ops;
> >>+	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> >>+	strlcpy(sd->name, config->dev_name, sizeof(sd->name));
> >>+
> >>+	ret = media_entity_init(&sd->entity, 0, NULL, 0);
> >>+	if (ret < 0)
> >>+		return ERR_PTR(ret);
> >>+
> >>+	sd->entity.type = MEDIA_ENT_T_V4L2_SUBDEV_FLASH;
> >>+
> >>+	ret = v4l2_flash_init_controls(v4l2_flash, config);
> >>+	if (ret < 0)
> >
> >You're missing media_entity_cleanup() here. How about adding a new label
> >below for that?
> 
> Right, thanks.
> 
> >>+		return ERR_PTR(ret);
> >>+
> >>+	of_node_get(led_cdev->dev->of_node);
> >>+
> >>+	ret = v4l2_async_register_subdev(sd);
> >>+	if (ret < 0)
> >>+		goto err_async_register_sd;
> >>+
> >>+	return v4l2_flash;
> >>+
> >>+err_async_register_sd:
> >>+	of_node_put(led_cdev->dev->of_node);
> >>+	v4l2_ctrl_handler_free(sd->ctrl_handler);
> >>+	media_entity_cleanup(&sd->entity);
> >>+
> >>+	return ERR_PTR(ret);
> >>+}
> >>+EXPORT_SYMBOL_GPL(v4l2_flash_init);
> >>+
> >>+void v4l2_flash_release(struct v4l2_flash *v4l2_flash)
> >>+{
> >>+	struct v4l2_subdev *sd = &v4l2_flash->sd;
> >>+	struct led_classdev *led_cdev = &v4l2_flash->fled_cdev->led_cdev;
> >>+
> >>+	v4l2_async_unregister_subdev(sd);
> >>+	of_node_put(led_cdev->dev->of_node);
> >>+	v4l2_ctrl_handler_free(sd->ctrl_handler);
> >>+	media_entity_cleanup(&sd->entity);
> >>+}
> >>+EXPORT_SYMBOL_GPL(v4l2_flash_release);
> >>+
> >>+MODULE_AUTHOR("Jacek Anaszewski <j.anaszewski@samsung.com>");
> >>+MODULE_DESCRIPTION("V4L2 Flash sub-device helpers");
> >>+MODULE_LICENSE("GPL v2");
> >>diff --git a/include/media/v4l2-flash.h b/include/media/v4l2-flash.h
> >>new file mode 100644
> >>index 0000000..cc0138d
> >>--- /dev/null
> >>+++ b/include/media/v4l2-flash.h
> >>@@ -0,0 +1,145 @@
> >>+/*
> >>+ * V4L2 Flash LED sub-device registration helpers.
> >>+ *
> >>+ *	Copyright (C) 2015 Samsung Electronics Co., Ltd
> >>+ *	Author: Jacek Anaszewski <j.anaszewski@samsung.com>
> >>+ *
> >>+ * This program is free software; you can redistribute it and/or modify
> >>+ * it under the terms of the GNU General Public License version 2 as
> >>+ * published by the Free Software Foundation.
> >>+ */
> >>+
> >>+#ifndef _V4L2_FLASH_H
> >>+#define _V4L2_FLASH_H
> >>+
> >>+#include <media/v4l2-ctrls.h>
> >>+#include <media/v4l2-subdev.h>
> >>+
> >>+struct led_classdev_flash;
> >>+struct led_classdev;
> >>+struct v4l2_flash;
> >>+enum led_brightness;
> >>+
> >>+enum ctrl_init_data_id {
> >>+	LED_MODE,
> >>+	TORCH_INTENSITY,
> >>+	FLASH_INTENSITY,
> >>+	INDICATOR_INTENSITY,
> >>+	FLASH_TIMEOUT,
> >>+	STROBE_SOURCE,
> >>+	/*
> >>+	 * Only above values are applicable to
> >>+	 * the 'ctrls' array in the struct v4l2_flash.
> >>+	 */
> >>+	FLASH_STROBE,
> >>+	STROBE_STOP,
> >>+	STROBE_STATUS,
> >>+	FLASH_FAULT,
> >>+	NUM_FLASH_CTRLS,
> >>+};
> >>+
> >>+/*
> >>+ * struct v4l2_flash_ctrl_data - flash control initialization data, filled
> >>+ *				basing on the features declared by the LED Flash
> >>+ *				class driver in the v4l2_flash_ctrl_config
> >>+ * @config:	initialization data for a control
> >>+ * @cid:	contains v4l2 flash control id if the config
> >>+ *		field was initialized, 0 otherwise
> >>+ */
> >>+struct v4l2_flash_ctrl_data {
> >>+	struct v4l2_ctrl_config config;
> >>+	u32 cid;
> >>+};
> >>+
> >>+struct v4l2_flash_ops {
> >>+	/* setup strobing the flash by hardware pin state assertion */
> >>+	int (*external_strobe_set)(struct v4l2_flash *v4l2_flash,
> >>+					bool enable);
> >>+	/* convert intensity to brightness in a device specific manner */
> >>+	enum led_brightness (*intensity_to_led_brightness)
> >>+		(struct v4l2_flash *v4l2_flash, s32 intensity);
> >>+	/* convert brightness to intensity in a device specific manner */
> >>+	s32 (*led_brightness_to_intensity)
> >>+		(struct v4l2_flash *v4l2_flash, enum led_brightness);
> >>+};
> >>+
> >>+/**
> >>+ * struct v4l2_flash_ctrl_config - V4L2 Flash controls initialization data
> >
> >This is a bit more than just about controls. How about dropping "_ctrl" from
> >the name?
> 
> Good point.
> 
> >>+ * @dev_name:			human readable device name
> >
> >Could you use "the name of the media entity, unique in the system" instead,
> >please?
> >
> >>+ * @intensity:			constraints for the led in a non-flash mode
> >>+ * @flash_intensity:		V4L2_CID_FLASH_INTENSITY constraints
> >>+ * @flash_timeout:		V4L2_CID_FLASH_TIMEOUT constraints
> >>+ * @flash_faults:		possible flash faults
> >
> >Please refer to documentation
> 
> Do you want to put here whole description from documentation?
> Or maybe only mention that faults can "prevent further use of some of
> the flash controls"?

No, just a pointer where the flash faults are defined, or which #defines
they use for example so the reader can find them easily.

> 
> >
> >>+ * @has_external_strobe:	external strobe capability
> >>+ * @indicator_led:		signifies that a led is of indicator type
> >>+ */
> >>+struct v4l2_flash_ctrl_config {
> >>+	char dev_name[32];
> >>+	struct v4l2_ctrl_config intensity;
> >>+	struct v4l2_ctrl_config flash_intensity;
> >>+	struct v4l2_ctrl_config flash_timeout;
> >
> >I think I may have suggested using v4l2_ctrl_config here, but currently the
> >drivers need to copy the values to v4l2_ctrl_config struct, instead of using
> >struct led_flash_setting which they have to use anyway.
> >
> >What would you think it'd be feasible to use led_flash_setting here as well?
> 
> I tried and it turned out that there was a room for even greater number
> of optimizations around flash settings and config initialization.

:-)

> 
> 
> >>+	u32 flash_faults;
> >>+	unsigned int has_external_strobe:1;
> >>+	unsigned int indicator_led:1;
> >>+};
> >>+
> >>+/**
> >>+ * struct v4l2_flash - Flash sub-device context
> >>+ * @fled_cdev:		LED Flash class device controlled by this sub-device
> >>+ * @ops:		V4L2 specific flash ops
> >>+ * @sd:			V4L2 sub-device
> >>+ * @hdl:		flash controls handler
> >>+ * @ctrls:		array of pointers to controls, whose values define
> >>+ *			the sub-device state
> >>+ */
> >>+struct v4l2_flash {
> >>+	struct led_classdev_flash *fled_cdev;
> >>+	const struct v4l2_flash_ops *ops;
> >>+
> >>+	struct v4l2_subdev sd;
> >>+	struct v4l2_ctrl_handler hdl;
> >>+	struct v4l2_ctrl *ctrls[STROBE_SOURCE + 1];
> >>+};
> >>+
> >>+static inline struct v4l2_flash *v4l2_subdev_to_v4l2_flash(
> >>+							struct v4l2_subdev *sd)
> >>+{
> >>+	return container_of(sd, struct v4l2_flash, sd);
> >>+}
> >>+
> >>+static inline struct v4l2_flash *v4l2_ctrl_to_v4l2_flash(struct v4l2_ctrl *c)
> >>+{
> >>+	return container_of(c->handler, struct v4l2_flash, hdl);
> >>+}
> >>+
> >>+#if IS_ENABLED(CONFIG_V4L2_FLASH_LED_CLASS)
> >>+/**
> >>+ * v4l2_flash_init - initialize V4L2 flash led sub-device
> >>+ * @fled_cdev:	the LED Flash class device to wrap
> >>+ * @flash_ops:	V4L2 Flash device ops
> >>+ * @config:	initialization data for V4L2 Flash controls
> >>+ *
> >>+ * Create V4L2 Flash sub-device wrapping given LED subsystem device.
> >>+ *
> >>+ * Returns: A valid pointer, or, when an error occurs, the return
> >>+ * value is encoded using ERR_PTR(). Use IS_ERR() to check and
> >>+ * PTR_ERR() to obtain the numeric return value.
> >>+ */
> >>+struct v4l2_flash *v4l2_flash_init(struct led_classdev_flash *fled_cdev,
> >>+				   const struct v4l2_flash_ops *ops,
> >>+				   struct v4l2_flash_ctrl_config *config);
> >>+
> >>+/**
> >>+ * v4l2_flash_release - release V4L2 Flash sub-device
> >>+ * @flash: the V4L2 Flash sub-device to release
> >>+ *
> >>+ * Release V4L2 Flash sub-device.
> >>+ */
> >>+void v4l2_flash_release(struct v4l2_flash *v4l2_flash);
> >>+
> >>+#else
> >>+#define v4l2_flash_init(fled_cdev, ops, config) (NULL)
> >>+#define v4l2_flash_release(v4l2_flash)
> >>+#endif /* CONFIG_V4L2_FLASH_LED_CLASS */
> >>+
> >>+#endif /* _V4L2_FLASH_H */
> >
> 
> 

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi	XMPP: sailus@retiisi.org.uk