media: uvcvideo: Implement UVC_EXT_GPIO_UNIT

Some devices can implement a physical switch to disable the input of the
camera on demand. Think of it like an elegant privacy sticker.

The system can read the status of the privacy switch via a GPIO.

It is important to know the status of the switch, e.g. to notify the
user when the camera will produce black frames and a videochat
application is used.

In some systems, the GPIO is connected to the main SoC instead of the
camera controller, with the connection reported by the system firmware
(ACPI or DT). In that case, the UVC device isn't aware of the GPIO. We
need to implement a virtual entity to handle the GPIO fully on the
driver side.

For example, for ACPI-based systems, the GPIO is reported in the USB
device object:

  Scope (\_SB.PCI0.XHCI.RHUB.HS07)
  {

	  /.../

    Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
    {
        GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
            "\\_SB.PCI0.GPIO", 0x00, ResourceConsumer, ,
            )
            {   // Pin list
                0x0064
            }
    })
    Name (_DSD, Package (0x02)  // _DSD: Device-Specific Data
    {
        ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301") /* Device Properties for _DSD */,
        Package (0x01)
        {
            Package (0x02)
            {
                "privacy-gpio",
                Package (0x04)
                {
                    \_SB.PCI0.XHCI.RHUB.HS07,
                    Zero,
                    Zero,
                    One
                }
            }
        }
    })
  }

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/uvc/uvc_ctrl.c

@@ -2291,6 +2291,9 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
 		} else if (UVC_ENTITY_TYPE(entity) == UVC_ITT_CAMERA) {
 			bmControls = entity->camera.bmControls;
 			bControlSize = entity->camera.bControlSize;
+		} else if (UVC_ENTITY_TYPE(entity) == UVC_EXT_GPIO_UNIT) {
+			bmControls = entity->gpio.bmControls;
+			bControlSize = entity->gpio.bControlSize;
 		}
 
 		/* Remove bogus/blacklisted controls */

drivers/media/usb/uvc/uvc_driver.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/atomic.h>
+#include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/module.h>
@@ -1020,6 +1021,7 @@ error:
 }
 
 static const u8 uvc_camera_guid[16] = UVC_GUID_UVC_CAMERA;
+static const u8 uvc_gpio_guid[16] = UVC_GUID_EXT_GPIO_CONTROLLER;
 static const u8 uvc_media_transport_input_guid[16] =
 	UVC_GUID_UVC_MEDIA_TRANSPORT_INPUT;
 static const u8 uvc_processing_guid[16] = UVC_GUID_UVC_PROCESSING;
@@ -1051,6 +1053,9 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
 	 * is initialized by the caller.
 	 */
 	switch (type) {
+	case UVC_EXT_GPIO_UNIT:
+		memcpy(entity->guid, uvc_gpio_guid, 16);
+		break;
 	case UVC_ITT_CAMERA:
 		memcpy(entity->guid, uvc_camera_guid, 16);
 		break;
@@ -1464,6 +1469,108 @@ next_descriptor:
 	return 0;
 }
 
+/* -----------------------------------------------------------------------------
+ * Privacy GPIO
+ */
+
+static void uvc_gpio_event(struct uvc_device *dev)
+{
+	struct uvc_entity *unit = dev->gpio_unit;
+	struct uvc_video_chain *chain;
+	u8 new_val;
+
+	if (!unit)
+		return;
+
+	new_val = gpiod_get_value_cansleep(unit->gpio.gpio_privacy);
+
+	/* GPIO entities are always on the first chain. */
+	chain = list_first_entry(&dev->chains, struct uvc_video_chain, list);
+	uvc_ctrl_status_event(chain, unit->controls, &new_val);
+}
+
+static int uvc_gpio_get_cur(struct uvc_device *dev, struct uvc_entity *entity,
+			    u8 cs, void *data, u16 size)
+{
+	if (cs != UVC_CT_PRIVACY_CONTROL || size < 1)
+		return -EINVAL;
+
+	*(u8 *)data = gpiod_get_value_cansleep(entity->gpio.gpio_privacy);
+
+	return 0;
+}
+
+static int uvc_gpio_get_info(struct uvc_device *dev, struct uvc_entity *entity,
+			     u8 cs, u8 *caps)
+{
+	if (cs != UVC_CT_PRIVACY_CONTROL)
+		return -EINVAL;
+
+	*caps = UVC_CONTROL_CAP_GET | UVC_CONTROL_CAP_AUTOUPDATE;
+	return 0;
+}
+
+static irqreturn_t uvc_gpio_irq(int irq, void *data)
+{
+	struct uvc_device *dev = data;
+
+	uvc_gpio_event(dev);
+	return IRQ_HANDLED;
+}
+
+static int uvc_gpio_parse(struct uvc_device *dev)
+{
+	struct uvc_entity *unit;
+	struct gpio_desc *gpio_privacy;
+	int irq;
+
+	gpio_privacy = devm_gpiod_get_optional(&dev->udev->dev, "privacy",
+					       GPIOD_IN);
+	if (IS_ERR_OR_NULL(gpio_privacy))
+		return PTR_ERR_OR_ZERO(gpio_privacy);
+
+	unit = uvc_alloc_entity(UVC_EXT_GPIO_UNIT, UVC_EXT_GPIO_UNIT_ID, 0, 1);
+	if (!unit)
+		return -ENOMEM;
+
+	irq = gpiod_to_irq(gpio_privacy);
+	if (irq < 0) {
+		if (irq != EPROBE_DEFER)
+			dev_err(&dev->udev->dev,
+				"No IRQ for privacy GPIO (%d)\n", irq);
+		return irq;
+	}
+
+	unit->gpio.gpio_privacy = gpio_privacy;
+	unit->gpio.irq = irq;
+	unit->gpio.bControlSize = 1;
+	unit->gpio.bmControls = (u8 *)unit + sizeof(*unit);
+	unit->gpio.bmControls[0] = 1;
+	unit->get_cur = uvc_gpio_get_cur;
+	unit->get_info = uvc_gpio_get_info;
+	strncpy(unit->name, "GPIO", sizeof(unit->name) - 1);
+
+	list_add_tail(&unit->list, &dev->entities);
+
+	dev->gpio_unit = unit;
+
+	return 0;
+}
+
+static int uvc_gpio_init_irq(struct uvc_device *dev)
+{
+	struct uvc_entity *unit = dev->gpio_unit;
+
+	if (!unit || unit->gpio.irq < 0)
+		return 0;
+
+	return devm_request_threaded_irq(&dev->udev->dev, unit->gpio.irq, NULL,
+					 uvc_gpio_irq,
+					 IRQF_ONESHOT | IRQF_TRIGGER_FALLING |
+					 IRQF_TRIGGER_RISING,
+					 "uvc_privacy_gpio", dev);
+}
+
 /* ------------------------------------------------------------------------
  * UVC device scan
  */
@@ -1953,6 +2060,13 @@ static int uvc_scan_device(struct uvc_device *dev)
 		return -1;
 	}
 
+	/* Add GPIO entity to the first chain. */
+	if (dev->gpio_unit) {
+		chain = list_first_entry(&dev->chains,
+					 struct uvc_video_chain, list);
+		list_add_tail(&dev->gpio_unit->chain, &chain->entities);
+	}
+
 	return 0;
 }
 
@@ -2285,6 +2399,12 @@ static int uvc_probe(struct usb_interface *intf,
 		goto error;
 	}
 
+	/* Parse the associated GPIOs. */
+	if (uvc_gpio_parse(dev) < 0) {
+		uvc_trace(UVC_TRACE_PROBE, "Unable to parse UVC GPIOs\n");
+		goto error;
+	}
+
 	uvc_printk(KERN_INFO, "Found UVC %u.%02x device %s (%04x:%04x)\n",
 		dev->uvc_version >> 8, dev->uvc_version & 0xff,
 		udev->product ? udev->product : "<unnamed>",
@@ -2335,6 +2455,13 @@ static int uvc_probe(struct usb_interface *intf,
 			"supported.\n", ret);
 	}
 
+	ret = uvc_gpio_init_irq(dev);
+	if (ret < 0) {
+		dev_err(&dev->udev->dev,
+			"Unable to request privacy GPIO IRQ (%d)\n", ret);
+		goto error;
+	}
+
 	uvc_trace(UVC_TRACE_PROBE, "UVC device initialized.\n");
 	usb_enable_autosuspend(udev);
 	return 0;

drivers/media/usb/uvc/uvc_entity.c

@@ -105,6 +105,7 @@ static int uvc_mc_init_entity(struct uvc_video_chain *chain,
 		case UVC_OTT_DISPLAY:
 		case UVC_OTT_MEDIA_TRANSPORT_OUTPUT:
 		case UVC_EXTERNAL_VENDOR_SPECIFIC:
+		case UVC_EXT_GPIO_UNIT:
 		default:
 			function = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
 			break;

drivers/media/usb/uvc/uvcvideo.h

@@ -6,6 +6,7 @@
 #error "The uvcvideo.h header is deprecated, use linux/uvcvideo.h instead."
 #endif /* __KERNEL__ */
 
+#include <linux/atomic.h>
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/usb.h>
@@ -37,6 +38,8 @@
 	(UVC_ENTITY_IS_TERM(entity) && \
 	((entity)->type & 0x8000) == UVC_TERM_OUTPUT)
 
+#define UVC_EXT_GPIO_UNIT		0x7ffe
+#define UVC_EXT_GPIO_UNIT_ID		0x100
 
 /* ------------------------------------------------------------------------
  * GUIDs
@@ -56,6 +59,9 @@
 #define UVC_GUID_UVC_SELECTOR \
 	{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
 	 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02}
+#define UVC_GUID_EXT_GPIO_CONTROLLER \
+	{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+	 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x03}
 
 #define UVC_GUID_FORMAT_MJPEG \
 	{ 'M',  'J',  'P',  'G', 0x00, 0x00, 0x10, 0x00, \
@@ -212,6 +218,7 @@
  * Structures.
  */
 
+struct gpio_desc;
 struct uvc_device;
 
 /* TODO: Put the most frequently accessed fields at the beginning of
@@ -353,6 +360,13 @@ struct uvc_entity {
 			u8  *bmControls;
 			u8  *bmControlsType;
 		} extension;
+
+		struct {
+			u8  bControlSize;
+			u8  *bmControls;
+			struct gpio_desc *gpio_privacy;
+			int irq;
+		} gpio;
 	};
 
 	u8 bNrInPins;
@@ -691,6 +705,8 @@ struct uvc_device {
 		struct uvc_control *ctrl;
 		const void *data;
 	} async_ctrl;
+
+	struct uvc_entity *gpio_unit;
 };
 
 enum uvc_handle_state {