Re: [PATCH v5 07/12] media: uvcvideo: Implement UVC_EXT_GPIO_UNIT

From: Laurent Pinchart
Date: Tue Dec 22 2020 - 03:34:57 EST

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In reply to: Ricardo Ribalda: "[PATCH v5 07/12] media: uvcvideo: Implement UVC_EXT_GPIO_UNIT"
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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@xxxxxxxxxxxx>
> ---
> 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
> + */
> +
> +
> +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

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In reply to: Ricardo Ribalda: "[PATCH v5 07/12] media: uvcvideo: Implement UVC_EXT_GPIO_UNIT"
Next in thread: Laurent Pinchart: "Re: [PATCH v5 07/12] media: uvcvideo: Implement UVC_EXT_GPIO_UNIT"
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