From f4c3dee21770b9b8817c80265b9f81eda1833731 Mon Sep 17 00:00:00 2001
From: Daniel Scally <dan.scally@ideasonboard.com>
Date: Tue, 15 Jul 2025 16:13:05 +0100
Subject: [PATCH] libcamera: V4L2Subdevice: Get device by regexp

Some kernel drivers give their entities names that will differ from
implementation to implementation; for example the drivers for the
Camera Receiver Unit and CSI-2 receiver in the RZ/V2H(P) SoC give their
entities names that include their memory address, in the format
"csi-16000400.csi2". Passing that entity name to
V4L2Subdevice::fromEntityName() is too inflexible given it would only
then work if that specific CSI-2 receiver were the one being used.

Add an overload for V4L2Subdevice::fromEntityName() to instead allow
users to pass a std::basic_regex, and use std::regex_search() instead
of a direct string comparison to find a matching entity. Ths allows
us to form regular expressions like "csi-[0-9a-f]{8}.csi2" to find
the entities.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 include/libcamera/internal/v4l2_subdevice.h |  3 +++
 src/libcamera/v4l2_subdevice.cpp            | 19 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/internal/v4l2_subdevice.h b/include/libcamera/internal/v4l2_subdevice.h
index c1cde1df..c37a82af 100644
--- a/include/libcamera/internal/v4l2_subdevice.h
+++ b/include/libcamera/internal/v4l2_subdevice.h
@@ -18,6 +18,7 @@
 
 #include <libcamera/base/class.h>
 #include <libcamera/base/log.h>
+#include <libcamera/base/regex.h>
 
 #include <libcamera/color_space.h>
 #include <libcamera/geometry.h>
@@ -163,6 +164,8 @@ public:
 
 	static std::unique_ptr<V4L2Subdevice>
 	fromEntityName(const MediaDevice *media, const std::string &entity);
+	static std::unique_ptr<V4L2Subdevice>
+	fromEntityName(const MediaDevice *media, const std::regex &entity);
 
 protected:
 	std::string logPrefix() const override;
diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
index b75edffe..19942460 100644
--- a/src/libcamera/v4l2_subdevice.cpp
+++ b/src/libcamera/v4l2_subdevice.cpp
@@ -1748,7 +1748,6 @@ const std::string &V4L2Subdevice::model()
  * \a media
  * \param[in] media The media device where the entity is registered
  * \param[in] entity The media entity name
- *
  * \return A newly created V4L2Subdevice on success, nullptr otherwise
  */
 std::unique_ptr<V4L2Subdevice>
@@ -1762,6 +1761,24 @@ V4L2Subdevice::fromEntityName(const MediaDevice *media,
 	return std::make_unique<V4L2Subdevice>(mediaEntity);
 }
 
+/**
+ * \brief Create a new video subdevice instance from an entity in media device
+ * \a media
+ * \param[in] media The media device where the entity is registered
+ * \param[in] entity A regex that will match the media entity's name
+ * \return A newly created V4L2Subdevice on success, nullptr otherwise
+ */
+std::unique_ptr<V4L2Subdevice>
+V4L2Subdevice::fromEntityName(const MediaDevice *media,
+			      const std::regex &entity)
+{
+	MediaEntity *mediaEntity = media->getEntityByName(entity);
+	if (!mediaEntity)
+		return nullptr;
+
+	return std::make_unique<V4L2Subdevice>(mediaEntity);
+}
+
 std::string V4L2Subdevice::logPrefix() const
 {
 	return "'" + entity_->name() + "'";