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From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Date: Thu, 04 Apr 2024 13:50:00 +0300
Subject: [PATCH 1/4] media: subdev: Add checks for subdev features
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Message-Id: <20240404-enable-streams-impro-v1-1-1017a35bbe07@ideasonboard.com>
References: <20240404-enable-streams-impro-v1-0-1017a35bbe07@ideasonboard.com>
In-Reply-To: <20240404-enable-streams-impro-v1-0-1017a35bbe07@ideasonboard.com>
To: Mauro Carvalho Chehab <mchehab@kernel.org>, 
 Hans Verkuil <hverkuil@xs4all.nl>, 
 Laurent Pinchart <laurent.pinchart@ideasonboard.com>, 
 Sakari Ailus <sakari.ailus@linux.intel.com>, 
 Umang Jain <umang.jain@ideasonboard.com>
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, 
 Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Add some checks to verify that the subdev driver implements required
features.

A subdevice that supports streams (V4L2_SUBDEV_FL_STREAMS) must do one
of the following:

- Implement neither .enable/disable_streams() nor .s_stream(), if the
  subdev is part of a video driver that uses an internal method to
  enable the subdev.
- Implement only .enable/disable_streams(), if support for legacy
  sink-side subdevices is not needed.
- Implement .enable/disable_streams() and .s_stream(), if support for
  legacy sink-side subdevices is needed.

At the moment the framework doesn't check this requirement. Add the
check.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 4c6198c48dd6..b90b5185e87f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1519,6 +1519,33 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
 				struct lock_class_key *key)
 {
 	struct v4l2_subdev_state *state;
+	struct device *dev = sd->dev;
+	bool has_disable_streams;
+	bool has_enable_streams;
+	bool has_s_stream;
+
+	/* Check that the subdevice implements the required features */
+
+	has_s_stream = sd->ops && sd->ops->video && sd->ops->video->s_stream;
+	has_enable_streams = sd->ops && sd->ops->pad && sd->ops->pad->enable_streams;
+	has_disable_streams = sd->ops && sd->ops->pad && sd->ops->pad->disable_streams;
+
+	if (has_enable_streams != has_disable_streams) {
+		dev_err(dev,
+			"subdev '%s' must implement both or neither of .enable_streams() and .disable_streams()\n",
+			sd->name);
+		return -EINVAL;
+	}
+
+	if (sd->flags & V4L2_SUBDEV_FL_STREAMS) {
+		if (has_s_stream && !has_enable_streams) {
+			dev_err(dev,
+				"subdev '%s' must implement .enable/disable_streams()\n",
+				sd->name);
+
+			return -EINVAL;
+		}
+	}
 
 	state = __v4l2_subdev_state_alloc(sd, name, key);
 	if (IS_ERR(state))

-- 
2.34.1