linux-kernel - [PATCH v6 2/8] media: uvcvideo: Add support for per-device control mapping overrides

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Date:   Wed, 15 Jun 2022 17:12:53 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org, senozhatsky@...omium.org, yunkec@...gle.com
Cc:     Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v6 2/8] media: uvcvideo: Add support for per-device control mapping overrides

Some devices do not implement all their controls in a way that complies
with the UVC specification. This is for instance the case for several
devices that do not support the disabled mode for the power line
frequency control. Add a mechanism to allow per-device control mapping
overrides to avoid errors when accessing non-compliant controls.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 35 ++++++++++++++++++++++++++------
 drivers/media/usb/uvc/uvcvideo.h |  1 +
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index a709ebbb4d69..092decfdaa62 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2403,9 +2403,8 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 {
 	const struct uvc_control_info *info = uvc_ctrls;
 	const struct uvc_control_info *iend = info + ARRAY_SIZE(uvc_ctrls);
-	const struct uvc_control_mapping *mapping = uvc_ctrl_mappings;
-	const struct uvc_control_mapping *mend =
-		mapping + ARRAY_SIZE(uvc_ctrl_mappings);
+	const struct uvc_control_mapping *mapping;
+	const struct uvc_control_mapping *mend;
 
 	/* XU controls initialization requires querying the device for control
 	 * information. As some buggy UVC devices will crash when queried
@@ -2433,14 +2432,38 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 	if (!ctrl->initialized)
 		return;
 
-	/* Process common mappings first. */
-	for (; mapping < mend; ++mapping) {
+	/*
+	 * First check if the device provides a custom mapping for this control,
+	 * used to override standard mappings for non-conformant devices. Don't
+	 * process standard mappings if a custom mapping is found. This
+	 * mechanism doesn't support combining standard and custom mappings for
+	 * a single control.
+	 */
+	if (chain->dev->info->mappings) {
+		bool custom = false;
+		unsigned int i;
+
+		for (i = 0; (mapping = chain->dev->info->mappings[i]); ++i) {
+			if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
+			    ctrl->info.selector == mapping->selector) {
+				__uvc_ctrl_add_mapping(chain, ctrl, mapping);
+				custom = true;
+			}
+		}
+
+		if (custom)
+			return;
+	}
+
+	/* Process common mappings next. */
+	mend = mapping + ARRAY_SIZE(uvc_ctrl_mappings);
+	for (mapping = uvc_ctrl_mappings; mapping < mend; ++mapping) {
 		if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
 		    ctrl->info.selector == mapping->selector)
 			__uvc_ctrl_add_mapping(chain, ctrl, mapping);
 	}
 
-	/* And then version-specific mappings. */
+	/* Finally process version-specific mappings. */
 	if (chain->dev->uvc_version < 0x0150) {
 		mapping = uvc_ctrl_mappings_uvc11;
 		mend = mapping + ARRAY_SIZE(uvc_ctrl_mappings_uvc11);
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index c5b4febd2d94..fff5c5c99a3d 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -667,6 +667,7 @@ struct uvc_device_info {
 	u32	quirks;
 	u32	meta_format;
 	u16	uvc_version;
+	const struct uvc_control_mapping **mappings;
 };
 
 struct uvc_device {
-- 
2.36.1.476.g0c4daa206d-goog