Re: [PATCH v4 9/9] media: uvcvideo: Implement UVC_QUIRK_PRIVACY_DURING_STREAM

From: Ricardo Ribalda
Date: Sun Dec 20 2020 - 23:54:41 EST

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In reply to: Laurent Pinchart: "Re: [PATCH v4 9/9] media: uvcvideo: Implement UVC_QUIRK_PRIVACY_DURING_STREAM"
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Hi Laurent

On Mon, Dec 21, 2020 at 3:08 AM Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Ricardo,
>
> On Mon, Dec 21, 2020 at 02:10:18AM +0100, Ricardo Ribalda wrote:
> > On Sun, Dec 20, 2020 at 6:22 PM Laurent Pinchart wrote:
> > > On Tue, Dec 15, 2020 at 04:44:39PM +0100, Ricardo Ribalda wrote:
> > > > Some devices, can only read the privacy_pin if the device is
> > > > streaming.
> > >
> > > :-(
> >
> > :"-(
> >
> > > > This patch implement a quirk for such devices, in order to avoid invalid
> > > > reads and/or spurious events.
> > > >
> > > > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> > > > ---
> > > > drivers/media/usb/uvc/uvc_driver.c | 97 ++++++++++++++++++++++++++----
> > > > drivers/media/usb/uvc/uvc_queue.c | 3 +
> > > > drivers/media/usb/uvc/uvcvideo.h | 6 ++
> > > > 3 files changed, 94 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > > index e49491250e87..61313019e226 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/dmi.h>
> > > > #include <linux/gpio/consumer.h>
> > > > #include <linux/kernel.h>
> > > > #include <linux/list.h>
> > > > @@ -1471,13 +1472,39 @@ static int uvc_parse_control(struct uvc_device *dev)
> > > > return 0;
> > > > }
> > > >
> > > > +static bool uvc_ext_gpio_is_streaming(struct uvc_device *dev)
> > > > +{
> > > > + struct uvc_streaming *streaming;
> > > > +
> > > > + list_for_each_entry(streaming, &dev->streams, list) {
> > > > + if (uvc_queue_streaming(&streaming->queue))
> > > > + return true;
> > > > + }
> > > > +
> > > > + return false;
> > > > +}
> > > > +
> > > > +/* Update the cached value and return true if it has changed */
> > > > +static bool uvc_gpio_update_value(struct uvc_entity *unit, u8 *new_val)
> > > > +{
> > > > + *new_val = gpiod_get_value(unit->gpio.gpio_privacy);
> > > > +
> > > > + return atomic_xchg(&unit->gpio.gpio_privacy_value, *new_val) !=
> > > > + *new_val;
> > >
> > > That's a weird indentation. Also, as the left hand side modifies
> > > *new_val, does C guarantee the order in which the two operands to != are
> > > evaluated ? Could the code be written in an easier to read way ?
> > >
> > > > +}
> > > > +
> > > > 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 = gpiod_get_value(entity->gpio.gpio_privacy);
> > > > + if ((dev->quirks & UVC_QUIRK_PRIVACY_DURING_STREAM) &&
> > > > + !uvc_ext_gpio_is_streaming(dev))
> > > > + return -EBUSY;
> > > > +
> > > > + uvc_gpio_update_value(entity, (uint8_t *)data);
> > > > +
> > > > return 0;
> > > > }
> > > >
> > > > @@ -1491,26 +1518,69 @@ static int uvc_gpio_get_info(struct uvc_device *dev, struct uvc_entity *entity,
> > > > return 0;
> > > > }
> > > >
> > > > -static irqreturn_t uvc_privacy_gpio_irq(int irq, void *data)
> > > > +static struct uvc_entity *uvc_find_ext_gpio_unit(struct uvc_device *dev)
> > > > {
> > > > - struct uvc_device *dev = data;
> > > > - struct uvc_video_chain *chain;
> > > > struct uvc_entity *unit;
> > > > - u8 value;
> > > >
> > > > - /* GPIO entities are always on 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)
> > > > - continue;
> > > > - value = gpiod_get_value(unit->gpio.gpio_privacy);
> > > > - uvc_ctrl_status_event(NULL, chain, unit->controls, &value);
> > > > - return IRQ_HANDLED;
> > > > + if (UVC_ENTITY_TYPE(unit) == UVC_EXT_GPIO_UNIT)
> > > > + return unit;
> > > > }
> > > >
> > > > + return unit;
> > > > +}
> > > > +
> > > > +void uvc_privacy_gpio_event(struct uvc_device *dev)
> > > > +{
> > > > + struct uvc_entity *unit;
> > > > + struct uvc_video_chain *chain;
> > > > + u8 new_value;
> > > > +
> > > > + unit = uvc_find_ext_gpio_unit(dev);
> > > > + if (WARN_ONCE(!unit, "Unable to find entity ext_gpio_unit"))
> > > > + return;
> > > > +
> > > > + if (!uvc_gpio_update_value(unit, &new_value))
> > > > + return;
> > >
> > > If VIDIOC_G_CTRL() is called before the IRQ is processed, this
> > > uvc_gpio_update_value() call will return false, and no event will be
> > > generated. I don't think that's right, and even should be generated
> > > every time the control changes.
> > >
> > I was almost sure that get_cur had also the events wired.... but no.
> >
> > > > +
> > > > + /* 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_value);
> > > > +}
> > > > +
> > > > +static irqreturn_t uvc_privacy_gpio_irq(int irq, void *data)
> > > > +{
> > > > + struct uvc_device *dev = data;
> > > > +
> > > > + /* Ignore privacy events during streamoff */
> > > > + if (dev->quirks & UVC_QUIRK_PRIVACY_DURING_STREAM)
> > > > + if (!uvc_ext_gpio_is_streaming(dev))
> > > > + return IRQ_HANDLED;
> > >
> > > if (dev->quirks & UVC_QUIRK_PRIVACY_DURING_STREAM) {
> > > if (!uvc_ext_gpio_is_streaming(dev))
> > > return IRQ_HANDLED;
> > > }
> > >
> > > There's a potential race condition with VIDIOC_STREAMON and
> > > VIDIOC_STREAMOFF. Could you explain what the device does exactly when
> > > not streaming ? As the GPIO isn't tied to the UVC controller, how comes
> > > the streaming state influences it ? Any hope the firmware could be fixed
> > > instead ?
> >
> > In the affected devices, the privacy_pin is an output of the camera
> > module instead of an independent pin.
>
> So the privacy switch is an input of a camera module, which then output
> its state on a GPIO instead of exposing it through the UVC privacy
> control ? Amazing design !

Dont kill the messenger...

>
> > When the camera is not streaming, the camera does not drive the pin,
> > so the system reads whatever pull-up, pull-down the pin is configured
> > by default in the firmware/hardware.
> >
> > Unfortunately the only way to fix it would be to change the module, or
> > the firmware of the module, and neigher things are not feasable :(. So
> > we have to use a quirk for them.
> > Future models have this fixed.
>
> Changing the hardware, obviously. Changing the firmware of the module...
> Someone needs to be scolded along the development chain, can you take
> care of that at least ? ;-)

Will do my best ;)

>
> Thinking more about this, do you have a use case for knowing the state
> of the privacy switch when not streaming ?

Notify user space that the switch has toggled, to provide visual
feedback of the action.

>
> > Regarding the race condition... The use of the atomic_t was to avoid
> > that race, but what I did not realise was that by default get_cur does
> > not send an event... So I am working on a new series, which also
> > includes a fix for the async_control wq.
> >
> > Thanks for your review!!!
> >
> > > > +
> > > > + uvc_privacy_gpio_event(dev);
> > > > +
> > > > return IRQ_HANDLED;
> > > > }
> > > >
> > > > +static const struct dmi_system_id privacy_valid_during_streamon[] = {
> > > > + {
> > > > + .ident = "HP Elite c1030 Chromebook",
> > > > + .matches = {
> > > > + DMI_MATCH(DMI_SYS_VENDOR, "HP"),
> > > > + DMI_MATCH(DMI_PRODUCT_NAME, "Jinlon"),
> > > > + },
> > > > + },
> > > > + {
> > > > + .ident = "HP Pro c640 Chromebook",
> > > > + .matches = {
> > > > + DMI_MATCH(DMI_SYS_VENDOR, "HP"),
> > > > + DMI_MATCH(DMI_PRODUCT_NAME, "Dratini"),
> > > > + },
> > > > + },
> > > > + { } /* terminate list */
> > > > +};
> > > > +
> > > > +
> > > > static int uvc_parse_gpio(struct uvc_device *dev)
> > > > {
> > > > struct uvc_entity *unit;
> > > > @@ -1545,6 +1615,9 @@ static int uvc_parse_gpio(struct uvc_device *dev)
> > > > if (irq == -EPROBE_DEFER)
> > > > return -EPROBE_DEFER;
> > > >
> > > > + if (dmi_check_system(privacy_valid_during_streamon))
> > > > + dev->quirks |= UVC_QUIRK_PRIVACY_DURING_STREAM;
> > > > +
> > > > if (irq < 0)
> > > > return 0;
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
> > > > index cd60c6c1749e..e800d491303f 100644
> > > > --- a/drivers/media/usb/uvc/uvc_queue.c
> > > > +++ b/drivers/media/usb/uvc/uvc_queue.c
> > > > @@ -337,9 +337,12 @@ int uvc_dequeue_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf,
> > > > int uvc_queue_streamon(struct uvc_video_queue *queue, enum v4l2_buf_type type)
> > > > {
> > > > int ret;
> > > > + struct uvc_streaming *stream = uvc_queue_to_stream(queue);
> > > >
> > > > mutex_lock(&queue->mutex);
> > > > ret = vb2_streamon(&queue->queue, type);
> > > > + if (stream->dev->quirks & UVC_QUIRK_PRIVACY_DURING_STREAM)
> > > > + uvc_privacy_gpio_event(stream->dev);
> > > > mutex_unlock(&queue->mutex);
> > > >
> > > > return ret;
> > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > > > index 2b5ba4b02d3a..2a95b3ed3ea8 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/gpio/consumer.h>
> > > > #include <linux/kernel.h>
> > > > #include <linux/poll.h>
> > > > @@ -209,6 +210,7 @@
> > > > #define UVC_QUIRK_RESTORE_CTRLS_ON_INIT 0x00000400
> > > > #define UVC_QUIRK_FORCE_Y8 0x00000800
> > > > #define UVC_QUIRK_FORCE_BPP 0x00001000
> > > > +#define UVC_QUIRK_PRIVACY_DURING_STREAM 0x00002000
> > > >
> > > > /* Format flags */
> > > > #define UVC_FMT_FLAG_COMPRESSED 0x00000001
> > > > @@ -359,6 +361,7 @@ struct uvc_entity {
> > > > u8 bControlSize;
> > > > u8 *bmControls;
> > > > struct gpio_desc *gpio_privacy;
> > > > + atomic_t gpio_privacy_value;
> > > > } gpio;
> > > > };
> > > >
> > > > @@ -815,6 +818,9 @@ extern const struct v4l2_file_operations uvc_fops;
> > > > int uvc_mc_register_entities(struct uvc_video_chain *chain);
> > > > void uvc_mc_cleanup_entity(struct uvc_entity *entity);
> > > >
> > > > +/* Privacy gpio */
> > > > +void uvc_privacy_gpio_event(struct uvc_device *dev);
> > > > +
> > > > /* Video */
> > > > int uvc_video_init(struct uvc_streaming *stream);
> > > > int uvc_video_suspend(struct uvc_streaming *stream);
>
> --
> Regards,
>
> Laurent Pinchart

--
Ricardo Ribalda

Next message: Florian Fainelli: "Re: [RFC PATCH v2 0/8] Adding the Sparx5 Switch Driver"
Previous message: Bjorn Andersson: "Re: [PATCH 2/3] arm64: dts: qcom: sm8150: Add PSCI idle states"
In reply to: Laurent Pinchart: "Re: [PATCH v4 9/9] media: uvcvideo: Implement UVC_QUIRK_PRIVACY_DURING_STREAM"
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