linux-kernel - [PATCH v2 4/4] media: uvcvideo: Announce the user our deprecation intentions

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Message-Id: <20241218-uvc-deprecate-v2-4-ab814139e983@chromium.org>
Date: Wed, 18 Dec 2024 21:39:11 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Hans de Goede <hdegoede@...hat.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v2 4/4] media: uvcvideo: Announce the user our deprecation
 intentions

If the user sets the nodrop parameter, print a deprecation warning once.
Hopefully they will come to the mailing list if it is an ABI change.

Now that we have a callback, take this chance to parse the parameter as
a boolean. We still say to userspace that it is a uint to avoid ABI
changes.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 10812a841587..d8e8675dd2cd 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -2424,8 +2424,25 @@ module_param_call(clock, uvc_clock_param_set, uvc_clock_param_get,
 MODULE_PARM_DESC(clock, "Video buffers timestamp clock");
 module_param_named(hwtimestamps, uvc_hw_timestamps_param, uint, 0644);
 MODULE_PARM_DESC(hwtimestamps, "Use hardware timestamps");
-module_param_named(nodrop, uvc_no_drop_param, uint, 0644);
+
+static int param_set_nodrop(const char *val, const struct kernel_param *kp)
+{
+	pr_warn_once("uvcvideo: "
+		     DEPRECATED
+		     "nodrop parameter will be eventually removed.\n");
+	return param_set_bool(val, kp);
+}
+
+static const struct kernel_param_ops param_ops_nodrop = {
+	.set = param_set_nodrop,
+	.get = param_get_uint,
+};
+
+param_check_uint(nodrop, &uvc_no_drop_param);
+module_param_cb(nodrop, &param_ops_nodrop, &uvc_no_drop_param, 0644);
+__MODULE_PARM_TYPE(nodrop, "uint");
 MODULE_PARM_DESC(nodrop, "Don't drop incomplete frames");
+
 module_param_named(quirks, uvc_quirks_param, uint, 0644);
 MODULE_PARM_DESC(quirks, "Forced device quirks");
 module_param_named(trace, uvc_dbg_param, uint, 0644);

-- 
2.47.1.613.gc27f4b7a9f-goog