[PATCH v2 2/3] media: uvcvideo: generalise the XU flags fixup to all controls

[Michael Jordan <jordan.mymail@gmail.com>]

uvc_ctrl_fixup_xu_info() holds a per-device table of controls whose
GET_INFO reply is wrong, and overrides the flags for them. It only runs
from uvc_ctrl_fill_xu_info(), so it can only correct extension unit
controls, but standard controls suffer from the same class of firmware
bug: a device can report a wrong capability byte for a Camera Terminal
or Processing Unit control just as easily.

Rename it to uvc_ctrl_fixup_flags() and call it at the start of
uvc_ctrl_get_flags(), where the flags are derived from GET_INFO for
every control, standard and XU alike. The fixup replaces the flags
wholesale, so when the table covers a control there is no point in
querying a device we already know gives a wrong answer: return early
and skip the GET_INFO request altogether. The call in
uvc_ctrl_fill_xu_info() is dropped, as uvc_ctrl_get_flags() now handles
the fixup for XU controls too.

No functional change for the devices already in the table: their
entries are XU controls, matched by entity and selector before as they
are now, and their flags come from the table either way. The only
difference is one GET_INFO request no longer issued per fixed-up
control.

Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 91 ++++++++++++++++++--------------
 1 file changed, 50 insertions(+), 41 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index aceb26310..64c90c380 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2852,6 +2852,48 @@ int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl)
  * Dynamic controls
  */
 
+static bool uvc_ctrl_fixup_flags(struct uvc_device *dev,
+				 const struct uvc_control *ctrl,
+				 struct uvc_control_info *info)
+{
+	struct uvc_ctrl_fixup {
+		struct usb_device_id id;
+		u8 entity;
+		u8 selector;
+		u8 flags;
+	};
+
+	static const struct uvc_ctrl_fixup fixups[] = {
+		{ { USB_DEVICE(0x046d, 0x08c2) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x046d, 0x08cc) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x046d, 0x0994) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+	};
+
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(fixups); ++i) {
+		if (!usb_match_one_id(dev->intf, &fixups[i].id))
+			continue;
+
+		if (fixups[i].entity == ctrl->entity->id &&
+		    fixups[i].selector == info->selector) {
+			info->flags = fixups[i].flags;
+			return true;
+		}
+	}
+
+	return false;
+}
+
 /*
  * Retrieve flags for a given control
  */
@@ -2862,6 +2904,14 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
 	u8 *data;
 	int ret;
 
+	/*
+	 * Some devices report bogus capabilities through GET_INFO. If the
+	 * fixup table covers this control, take the flags from the table and
+	 * skip the query altogether.
+	 */
+	if (uvc_ctrl_fixup_flags(dev, ctrl, info))
+		return 0;
+
 	data = kmalloc(1, GFP_KERNEL);
 	if (data == NULL)
 		return -ENOMEM;
@@ -2893,45 +2943,6 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
 	return ret;
 }
 
-static void uvc_ctrl_fixup_xu_info(struct uvc_device *dev,
-	const struct uvc_control *ctrl, struct uvc_control_info *info)
-{
-	struct uvc_ctrl_fixup {
-		struct usb_device_id id;
-		u8 entity;
-		u8 selector;
-		u8 flags;
-	};
-
-	static const struct uvc_ctrl_fixup fixups[] = {
-		{ { USB_DEVICE(0x046d, 0x08c2) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-		{ { USB_DEVICE(0x046d, 0x08cc) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-		{ { USB_DEVICE(0x046d, 0x0994) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-	};
-
-	unsigned int i;
-
-	for (i = 0; i < ARRAY_SIZE(fixups); ++i) {
-		if (!usb_match_one_id(dev->intf, &fixups[i].id))
-			continue;
-
-		if (fixups[i].entity == ctrl->entity->id &&
-		    fixups[i].selector == info->selector) {
-			info->flags = fixups[i].flags;
-			return;
-		}
-	}
-}
-
 /*
  * Query control information (size and flags) for XU controls.
  */
@@ -2972,8 +2983,6 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,
 		goto done;
 	}
 
-	uvc_ctrl_fixup_xu_info(dev, ctrl, info);
-
 	uvc_dbg(dev, CONTROL,
 		"XU control %pUl/%u queried: len %u, flags { get %u set %u auto %u }\n",
 		info->entity, info->selector, info->size,
-- 
2.43.0