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Date:   Tue, 22 Dec 2020 10:37:37 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Ricardo Ribalda <ribalda@chromium.org>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 07/12] media: uvcvideo: Implement UVC_EXT_GPIO_UNIT
Message-ID: <X+GwUbHaU3/j9LX6@pendragon.ideasonboard.com>
References: <20201221164819.792019-1-ribalda@chromium.org>
 <20201221164819.792019-8-ribalda@chromium.org>
 <X+GvbpC0vhitCHRo@pendragon.ideasonboard.com>
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In-Reply-To: <X+GvbpC0vhitCHRo@pendragon.ideasonboard.com>
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On Tue, Dec 22, 2020 at 10:33:52AM +0200, Laurent Pinchart wrote:
> Hi Ricardo,
> 
> Thank you for the patch.
> 
> On Mon, Dec 21, 2020 at 05:48:14PM +0100, Ricardo Ribalda wrote:
> > 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 main SoC instead of the
> > camera controller, with the connected reported by the system firmware
> 
> s/connected/connection/
> 
> > (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>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c   |   7 ++
> >  drivers/media/usb/uvc/uvc_driver.c | 156 +++++++++++++++++++++++++++++
> >  drivers/media/usb/uvc/uvc_entity.c |   1 +
> >  drivers/media/usb/uvc/uvcvideo.h   |  16 +++
> >  4 files changed, 180 insertions(+)
> > 
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 528254230535..a430fa666897 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -1300,6 +1300,10 @@ static void __uvc_ctrl_status_event_work(struct uvc_device *dev,
> >  
> >  	mutex_unlock(&chain->ctrl_mutex);
> >  
> > +	/* Events not started by the UVC device. E.g. the GPIO unit */
> > +	if (!w->urb)
> > +		return;
> > +
> >  	/* Resubmit the URB. */
> >  	w->urb->interval = dev->int_ep->desc.bInterval;
> >  	ret = usb_submit_urb(w->urb, GFP_KERNEL);
> > @@ -2317,6 +2321,9 @@ 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 */
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index c0c5f75ade40..72516101fdd0 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>
> > @@ -1020,6 +1021,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> >  }
> >  
> >  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 +1469,137 @@ static int uvc_parse_control(struct uvc_device *dev)
> >  	return 0;
> >  }
> >  
> > +/* -----------------------------------------------------------------------------
> > + * Privacy GPIO
> > + */
> > +
> > +

And there's an extra blank line here.

> > +static u8 uvc_gpio_update_value(struct uvc_device *dev,
> > +				struct uvc_entity *unit)
> > +{
> > +	struct uvc_video_chain *chain;
> > +	u8 gpio_val, old_val, new_val;
> > +
> > +	gpio_val = new_val = gpiod_get_value_cansleep(unit->gpio.gpio_privacy);
> > +
> > +	old_val = atomic_xchg(&unit->gpio.gpio_privacy_value, gpio_val);
> > +	if (new_val == old_val)
> > +		return new_val;
> > +
> > +	/* GPIO entities are always on the first chain. */
> > +	chain = list_first_entry(&dev->chains, struct uvc_video_chain, list);
> > +	uvc_ctrl_status_event(NULL, chain, unit->controls, &new_val);
> > +
> > +	return 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;
> > +
> > +	*(uint8_t *)data = uvc_gpio_update_value(dev, entity);
> 
> s/uint8_t/u8/
> 
> Do we really need to generate an event when the GPIO is read, if there's
> no IRQ support ?
> 
> > +	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 struct uvc_entity *uvc_gpio_find_entity(struct uvc_device *dev)
> > +{
> > +	struct uvc_video_chain *chain;
> > +	struct uvc_entity *unit;
> > +
> > +	/* GPIO entities are always on the first chain. */
> > +	chain = list_first_entry(&dev->chains, struct uvc_video_chain, list);
> > +	list_for_each_entry(unit, &chain->entities, chain) {
> > +		if (UVC_ENTITY_TYPE(unit) == UVC_EXT_GPIO_UNIT)
> > +			return unit;
> > +	}
> 
> As there can only be a single GPIO entity, would it make sense to store
> a pointer to it in struct uvc_device to avoid walking the chain every
> time ?
> 
> > +
> > +	return NULL;
> > +}
> > +
> > +static irqreturn_t uvc_gpio_irq(int irq, void *data)
> > +{
> > +	struct uvc_device *dev = data;
> > +	struct uvc_entity *unit;
> > +
> > +	unit = uvc_gpio_find_entity(dev);
> > +	if (!unit)
> > +		return IRQ_HANDLED;
> > +
> > +	uvc_gpio_update_value(dev, unit);
> > +	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 == -EPROBE_DEFER)
> > +		return -EPROBE_DEFER;
> > +
> > +	if (irq < 0)
> > +		dev_warn(&dev->udev->dev,
> > +		       "Unable to find privacy_gpio: %d\n", irq);
> 
> That's not right, the GPIO is found, it's only the IRQ that is
> unsupported.
> 
> 		dev_warn(&dev->udev->dev,
> 			 "No IRQ for privacy GPIO (%d)\n", irq);
> 
> > +
> > +	atomic_set(&unit->gpio.gpio_privacy_value, -1);
> > +	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;
> > +
> > +	sprintf(unit->name, "GPIO");
> 
> strncpy() would be simpler.
> 
> > +
> > +	list_add_tail(&unit->list, &dev->entities);
> > +
> > +	return 0;
> > +}
> > +
> > +static int uvc_gpio_init_irq(struct uvc_device *dev)
> > +{
> > +	int ret;
> > +	struct uvc_entity *unit;
> 
> Could you please swap those two lines ?
> 
> > +
> > +	unit = uvc_gpio_find_entity(dev);
> > +	if (!unit)
> > +		return 0;
> > +
> > +	if (unit->gpio.irq < 0)
> > +		return 0;
> > +
> > +	ret = devm_request_threaded_irq(&dev->udev->dev, unit->gpio.irq, NULL,
> > +					uvc_gpio_irq,
> > +					IRQF_ONESHOT | IRQF_TRIGGER_FALLING |
> > +					 IRQF_TRIGGER_RISING,
> 
> Extra space in the indentation.
> 
> > +					"uvc_privacy_gpio", dev);
> > +	return ret;
> 
> No need for a ret variable, you can write
> 
> 	return devm_request_threaded_irq(...);
> 
> (unless you want to move the error message here, see below).
> 
> > +}
> > +
> >  /* ------------------------------------------------------------------------
> >   * UVC device scan
> >   */
> > @@ -1915,6 +2051,7 @@ static int uvc_scan_device(struct uvc_device *dev)
> >  {
> >  	struct uvc_video_chain *chain;
> >  	struct uvc_entity *term;
> > +	struct uvc_entity *unit;
> >  
> >  	list_for_each_entry(term, &dev->entities, list) {
> >  		if (!UVC_ENTITY_IS_OTERM(term))
> > @@ -1953,6 +2090,13 @@ 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(unit, &dev->entities, list) {
> > +		if (UVC_ENTITY_TYPE(unit) == UVC_EXT_GPIO_UNIT)
> > +			list_add_tail(&unit->chain, &chain->entities);
> > +	}
> > +
> >  	return 0;
> >  }
> >  
> > @@ -2285,6 +2429,12 @@ 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>",
> > @@ -2329,6 +2479,12 @@ static int uvc_probe(struct usb_interface *intf,
> >  			"supported.\n", ret);
> >  	}
> >  
> > +	ret = uvc_gpio_init_irq(dev);
> > +	if (ret < 0)
> > +		dev_warn(&dev->udev->dev,
> > +			 "Unable to request uvc_privacy_gpio irq %d. Continuing wihtout privacy events\n",
> 
> s/uvc_privacy_gpio irq/privacy GPIO IRQ/ ?
> 
> > +			 ret);
> 
> This could be moved to uvc_gpio_init_irq(), up to you.
> 
> > +
> >  	uvc_trace(UVC_TRACE_PROBE, "UVC device initialized.\n");
> >  	usb_enable_autosuspend(udev);
> >  	return 0;
> > diff --git a/drivers/media/usb/uvc/uvc_entity.c b/drivers/media/usb/uvc/uvc_entity.c
> > index ca3a9c2eec27..6a9ba5b498db 100644
> > --- a/drivers/media/usb/uvc/uvc_entity.c
> > +++ b/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;
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 6edbf79b2ff1..079a407ebba5 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/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, \
> > @@ -278,6 +284,8 @@ struct uvc_format_desc {
> >  	u32 fcc;
> >  };
> >  
> > +struct gpio_desc;
> > +
> 
> This could be moved a bit up, with the other forward declaration.
> 
> >  /* The term 'entity' refers to both UVC units and UVC terminals.
> >   *
> >   * The type field is either the terminal type (wTerminalType in the terminal
> > @@ -353,6 +361,14 @@ struct uvc_entity {
> >  			u8  *bmControls;
> >  			u8  *bmControlsType;
> >  		} extension;
> > +
> > +		struct {
> > +			u8  bControlSize;
> > +			u8  *bmControls;
> > +			struct gpio_desc *gpio_privacy;
> > +			int irq;
> > +			atomic_t gpio_privacy_value;
> > +		} gpio;
> >  	};
> >  
> >  	u8 bNrInPins;

-- 
Regards,

Laurent Pinchart