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From:   Ricardo Ribalda <ribalda@chromium.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Ricardo Ribalda <ribalda@chromium.org>
Subject: [PATCH v3 1/2] media: uvcvideo: Only create input devs if hw supports it
Date:   Mon, 24 Jan 2022 20:00:12 +0100
Message-Id: <20220124190013.221601-1-ribalda@chromium.org>
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Examine the stream headers to figure out if the device has a GPIO and
can be used as an input.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_status.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 753c8226db70..3ef0b281ffc5 100644
--- a/drivers/media/usb/uvc/uvc_status.c
+++ b/drivers/media/usb/uvc/uvc_status.c
@@ -18,11 +18,34 @@
  * Input device
  */
 #ifdef CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV
+
+static bool uvc_input_has_button(struct uvc_device *dev)
+{
+	struct uvc_streaming *stream;
+
+	/*
+	 * The device has GPIO button event if both bTriggerSupport and
+	 * bTriggerUsage are one. Otherwise the camera button does not
+	 * exist or is handled automatically by the camera without host
+	 * driver or client application intervention.
+	 */
+	list_for_each_entry(stream, &dev->streams, list) {
+		if (stream->header.bTriggerSupport == 1 &&
+		    stream->header.bTriggerUsage == 1)
+			return true;
+	}
+
+	return false;
+}
+
 static int uvc_input_init(struct uvc_device *dev)
 {
 	struct input_dev *input;
 	int ret;
 
+	if (!uvc_input_has_button(dev))
+		return 0;
+
 	input = input_allocate_device();
 	if (input == NULL)
 		return -ENOMEM;
-- 
2.35.0.rc0.227.g00780c9af4-goog