linux-kernel - [PATCH 3/4] media: uvcvideo: Run uvc_ctrl_init

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Message-Id: <20250818-uvc-iq-switch-v1-3-f7ea5e740ddd@chromium.org>
Date: Mon, 18 Aug 2025 20:15:38 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Hans de Goede <hansg@...nel.org>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans Verkuil <hverkuil@...nel.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-usb@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH 3/4] media: uvcvideo: Run uvc_ctrl_init_ctrl for all
 controls

The function uvc_ctrl_init_ctrl() is called for every control for every
entity, but it exits early if the entity is a extension unit. The comment
claims that this is done to avoid querying XU controls during probe.

We only query a control if its entity GUIDs and index matches the
uvc_ctrls list. There are only controls for the following GUIDs:
UVC_GUID_UVC_PROCESSING, UVC_GUID_UVC_CAMERA and
UVC_GUID_EXT_GPIO_CONTROLLER.

In other words, XU controls will not be queried even without this
condition.

In future patches we want to add ChromeOS XU controls that need to the
initialized. We will make sure that all cameras with ChromeOS XU can
be queried at probe time.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index efe609d7087752cb2ef516eef0fce12acd13e747..ff975f96e1325532e2299047c07de5d1b9cf09db 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -3181,15 +3181,6 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 {
 	unsigned int i;
 
-	/*
-	 * XU controls initialization requires querying the device for control
-	 * information. As some buggy UVC devices will crash when queried
-	 * repeatedly in a tight loop, delay XU controls initialization until
-	 * first use.
-	 */
-	if (UVC_ENTITY_TYPE(ctrl->entity) == UVC_VC_EXTENSION_UNIT)
-		return;
-
 	for (i = 0; i < ARRAY_SIZE(uvc_ctrls); ++i) {
 		const struct uvc_control_info *info = &uvc_ctrls[i];
 

-- 
2.51.0.rc1.167.g924127e9c0-goog