[PATCH 5/6] media: uvcvideo: Implement UVC_GPIO_UNIT

[Ricardo Ribalda <ribalda@chromium.org>]

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.

Since the uvc device is not aware of this pin (and it should't), we need
to implement a virtual entity that can interact with such pin.

The location of the GPIO is specified via acpi or DT. on the usb device Eg:

    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>
---
 drivers/media/usb/uvc/uvc_ctrl.c   |  3 ++
 drivers/media/usb/uvc/uvc_driver.c | 72 ++++++++++++++++++++++++++++++
 drivers/media/usb/uvc/uvcvideo.h   |  8 ++++
 3 files changed, 83 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 786498e66646..3a49a1326a90 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2332,6 +2332,9 @@ 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_GPIO_UNIT) {
+			bmControls = entity->gpio.bmControls;
+			bControlSize = entity->gpio.bControlSize;
 		}
 
 		/* Remove bogus/blacklisted controls */
diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index ddb9eaa11be7..180e503e900f 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/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>
@@ -1440,6 +1441,58 @@ static int uvc_parse_control(struct uvc_device *dev)
 	return 0;
 }
 
+static int uvc_gpio_get_cur(struct uvc_entity *entity, u8 cs, void *data, u16 size)
+{
+	if ((cs != UVC_CT_PRIVACY_CONTROL) || (size < 1))
+		return -EINVAL;
+
+	*(uint8_t *)data = gpiod_get_value(entity->gpio.gpio_privacy);
+	return 0;
+}
+
+static int uvc_gpio_get_info(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 int uvc_parse_gpio(struct uvc_device *dev)
+{
+	struct uvc_entity *unit;
+	struct gpio_desc *gpio_privacy;
+	int irq;
+	int ret;
+
+	gpio_privacy = devm_gpiod_get_optional(&dev->udev->dev, "privacy", GPIOD_IN);
+
+	if (IS_ERR(gpio_privacy))
+		return PTR_ERR(gpio_privacy);
+
+	if (!gpio_privacy)
+		return 0;
+
+	unit = uvc_alloc_entity(UVC_GPIO_UNIT, 0xff, 1, 2);
+	if (!unit)
+		return -ENOMEM;
+
+	unit->gpio.gpio_privacy = gpio_privacy;
+	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;
+
+	sprintf(unit->name, "GPIO Unit");
+
+	list_add_tail(&unit->list, &dev->entities);
+
+	return 0;
+}
+
 /* ------------------------------------------------------------------------
  * UVC device scan
  */
@@ -1532,6 +1585,12 @@ static int uvc_scan_chain_entity(struct uvc_video_chain *chain,
 
 		break;
 
+	case UVC_GPIO_UNIT:
+		if (uvc_trace_param & UVC_TRACE_PROBE)
+			printk(KERN_CONT " GPIO %d", entity->id);
+
+		break;
+
 	case UVC_TT_STREAMING:
 		if (UVC_ENTITY_IS_ITERM(entity)) {
 			if (uvc_trace_param & UVC_TRACE_PROBE)
@@ -1929,6 +1988,13 @@ static int uvc_scan_device(struct uvc_device *dev)
 		return -1;
 	}
 
+	/* Add GPIO entities to the first_chain */
+	chain = list_first_entry(&dev->chains, struct uvc_video_chain, list);
+	list_for_each_entry(term, &dev->entities, list) {
+		if (UVC_ENTITY_TYPE(term) == UVC_GPIO_UNIT)
+			list_add_tail(&term->chain, &chain->entities);
+	}
+
 	return 0;
 }
 
@@ -2261,6 +2327,12 @@ static int uvc_probe(struct usb_interface *intf,
 		goto error;
 	}
 
+	/* Parse the associated GPIOs */
+	if (uvc_parse_gpio(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>",
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index a493bc383d3e..7ca78005b6a9 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/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/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/usb.h>
@@ -37,6 +38,7 @@
 	(UVC_ENTITY_IS_TERM(entity) && \
 	((entity)->type & 0x8000) == UVC_TERM_OUTPUT)
 
+#define UVC_GPIO_UNIT 0x7ffe
 
 /* ------------------------------------------------------------------------
  * GUIDs
@@ -351,6 +353,12 @@ struct uvc_entity {
 			u8  *bmControls;
 			u8  *bmControlsType;
 		} extension;
+
+		struct {
+			u8  bControlSize;
+			u8  *bmControls;
+			struct gpio_desc *gpio_privacy;
+		} gpio;
 	};
 
 	u8 bNrInPins;
-- 
2.29.0.rc1.297.gfa9743e501-goog