linux-kernel - [PATCH v2 1/8] media: uvcvideo: Only create input devs if hw supports it

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Message-Id: <20220920-resend-powersave-v2-1-5135d1bb1c38@chromium.org>
Date:   Tue, 25 Oct 2022 16:34:22 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Max Staudt <mstaudt@...gle.com>, linux-media@...r.kernel.org,
        Tomasz Figa <tfiga@...omium.org>, linux-kernel@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>
Subject: [PATCH v2 1/8] media: uvcvideo: Only create input devs if hw supports it

Examine the stream headers to figure out if the device has a button and
can be used as an input.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 7518ffce22ed..cb90aff344bc 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 button events 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;

-- 
b4 0.11.0-dev-d93f8