linux-kernel - [PATCH v2 3/7] media: uvcvideo: Probe the PLF characteristics

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Message-Id: <20240610-billion-v2-3-38e861475f85@chromium.org>
Date: Mon, 10 Jun 2024 23:09:54 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v2 3/7] media: uvcvideo: Probe the PLF characteristics

The UVC 1.5 standard defines 4 values for the PLF control: Off, 50Hz,
60Hz and Auto. But it does not clearly define if all the values must be
implemented or not.

Instead of just using the UVC version to determine what the PLF control
can do, probe it.

Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 52 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 47 insertions(+), 5 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index d82cfc56dfd5..5b77ac308c84 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -495,18 +495,60 @@ static const struct uvc_control_mapping uvc_ctrl_power_line_mapping_uvc15 = {
 				  V4L2_CID_POWER_LINE_FREQUENCY_DISABLED),
 };
 
-static int __uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
+static int __uvc_ctrl_add_mapping_to_list(struct uvc_video_chain *chain,
 	struct uvc_control *ctrl, const struct uvc_control_mapping *mapping);
 
 static int uvc_ctrl_add_plf_mapping(struct uvc_video_chain *chain,
 	struct uvc_control *ctrl, const struct uvc_control_mapping *mapping)
 {
+	const struct uvc_control_mapping *out_mapping =
+					&uvc_ctrl_power_line_mapping_uvc11;
+	u8 *buf __free(kfree) = NULL;
+	u8 init_val;
+	int ret;
+
+	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	/* Save the default PLF value, so we can restore it. */
+	ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	/* If we cannot read the control skip it. */
+	if (ret)
+		return ret;
+	init_val = *buf;
+
+	/* If PLF value cannot be set to off, it is limited. */
+	*buf = V4L2_CID_POWER_LINE_FREQUENCY_DISABLED;
+	ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	if (ret)
+		return __uvc_ctrl_add_mapping_to_list(chain, ctrl,
+					&uvc_ctrl_power_line_mapping_limited);
+
+	/* UVC 1.1 does not define auto, we can exit. */
 	if (chain->dev->uvc_version < 0x150)
-		return __uvc_ctrl_add_mapping(chain, ctrl,
-					      &uvc_ctrl_power_line_mapping_uvc11);
+		goto end;
+
+	/* Check if the device supports auto. */
+	*buf = V4L2_CID_POWER_LINE_FREQUENCY_AUTO;
+	ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	if (!ret)
+		out_mapping = &uvc_ctrl_power_line_mapping_uvc15;
+
+end:
+	/* Restore initial value and add mapping. */
+	*buf = init_val;
+	uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+		       chain->dev->intfnum, ctrl->info.selector,
+		       buf, sizeof(*buf));
 
-	return __uvc_ctrl_add_mapping(chain, ctrl,
-				      &uvc_ctrl_power_line_mapping_uvc15);
+	return __uvc_ctrl_add_mapping_to_list(chain, ctrl, out_mapping);
 }
 
 static const struct uvc_control_mapping uvc_ctrl_mappings[] = {

-- 
2.45.2.505.gda0bf45e8d-goog