| Message ID | 20250725-multicontext-v1-7-ea558291e101@ideasonboard.com |
|---|---|
| State | New |
| Headers | show |
| Series |
|
| Related | show |
Hi Jacopo, Thank you for the patch, On Fri, 2025-07-25 at 12:33 +0200, Jacopo Mondi wrote: > Introduce the MediaContext class that represents a media device > context to which video devices and subdevices can be bound to. > > A MediaContext can be created from a MediaDevice (which does not > support multi-context) and from SharedMediaDevice (which supports > multi-context). > > Binding devices to a MediaContext created from MediaDevice is a nop, > while MediaContext created from SharedMediaDevice perform proper > bindings. > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> > --- > include/libcamera/internal/media_device.h | 23 ++++- > src/libcamera/media_device.cpp | 135 > ++++++++++++++++++++++++++++++ > 2 files changed, 157 insertions(+), 1 deletion(-) > > diff --git a/include/libcamera/internal/media_device.h > b/include/libcamera/internal/media_device.h > index > ea0e9d66009933bbb9613d27423d2f951520c887..2dbfcc447d84bb6a1eee4ed598d > 22b5cc45adbe9 100644 > --- a/include/libcamera/internal/media_device.h > +++ b/include/libcamera/internal/media_device.h > @@ -21,6 +21,9 @@ > > namespace libcamera { > > +class V4L2VideoDevice; > +class V4L2Subdevice; > + > class MediaDeviceFactory > { > public: > @@ -28,6 +31,19 @@ public: > createMediaDevice(const std::string &deviceNode); > }; > > +class MediaContext > +{ > +public: > + MediaContext(); > + MediaContext(UniqueFD &&fd); > + > + int bindDevice(V4L2VideoDevice *dev); > + int bindDevice(V4L2Subdevice *dev); > + > +private: > + UniqueFD fd_; > +}; > + > class MediaDevice : protected Loggable > { > public: > @@ -63,10 +79,14 @@ public: > > std::vector<MediaEntity *> locateEntities(unsigned int > function); > > + virtual std::unique_ptr<MediaContext> createContext(); > + > protected: > MediaDevice(const std::string &deviceNode); > std::string logPrefix() const override; > > + std::string deviceNode_; > + > private: > friend class MediaDeviceFactory; > > @@ -88,7 +108,6 @@ private: > int setupLink(const MediaLink *link, unsigned int flags); > > std::string driver_; > - std::string deviceNode_; > std::string model_; > unsigned int version_; > unsigned int hwRevision_; > @@ -111,6 +130,8 @@ public: > bool lock() override; > void unlock() override; > > + std::unique_ptr<MediaContext> createContext() override; > + > private: > friend class MediaDeviceFactory; > > diff --git a/src/libcamera/media_device.cpp > b/src/libcamera/media_device.cpp > index > 70d073f964bde0236585de083baca4cd9c30d193..2b7df346ad9916cf22641ea770e > 0a1507921d89d 100644 > --- a/src/libcamera/media_device.cpp > +++ b/src/libcamera/media_device.cpp > @@ -21,6 +21,9 @@ > > #include <libcamera/base/log.h> > > +#include "libcamera/internal/v4l2_subdevice.h" > +#include "libcamera/internal/v4l2_videodevice.h" > + > /** > * \file media_device.h > * \brief Provide a representation of a Linux kernel Media > Controller device > @@ -81,6 +84,99 @@ MediaDeviceFactory::createMediaDevice(const > std::string &deviceNode) > return std::unique_ptr<MediaDevice>(new > MediaDevice(deviceNode)); > } > > +/** > + * \class MediaContext > + * \brief Represents a media device context > + * > + * A media device context is obtained from a MediaDevice or a > SharedMediaDevice > + * instance with the MediaDevice::createContext() and > + * SharedMediaDevice::createContext() functions. > + * > + * MediaContext instances obtained from a MediaDevice that does not > support > + * multi-context operations will not have a valid file descriptor > associated as > + * the media device they are created from doesn't support multiple > open. For > + * this reason binding a device to a context that is obtained from a > MediaDevice > + * is a nop. > + * > + * MediaContext instances obtained from a SharedMediaDevice that > supports > + * multi-context operations owns the file descriptor that identifies > the media > + * context, obtained by opening the media device multiple times and > provided to > + * the context at creation time. Binding devices to a context > obtained from a > + * SharedMediaDevice associates the devices to an execution context > which > + * remains valid until the last bound device stays valid. > + * > + * Users of this class can bind devices on valid and invalid > MultiContext > + * instances alike. If the kernel driver supports multi-context > operations > + * then the device can be opened multiple times and multiple > contexts can be > + * created to which devices can be bound to. If the kernel driver > doesn't > + * support multi-context operations then it can be opened a single > time only > + * and a creating contexts and bindings devices to it is effectively > a nop. > + */ > + > +/** > + * \brief Constructs a MediaContext not associated to any media > device context > + * > + * Constructs a media device context not associated to any valid > media device > + * context file descriptor. Binding devices to such media device > context > + * is effectively a nop. > + */ > +MediaContext::MediaContext() > +{ > +} > + > +/** > + * \brief Construct a MediaContext associated to a valid media > device context > + * \param[in] fd The file descriptor that identifies a media device > context > + * > + * Construct a media device context to which devices can be bound > to. > + * > + * Constructing a MediaContext with an associated valid media device > context > + * allows to create isolated execution contexts by binding devices > to it. > + * > + * The file descriptor \a fd obtained by opening the media device > and that > + * identifies the media device context is moved in the newly > constructed > + * MediaContext which maintains its ownership and automatically > closes it at > + * destruction time. > + */ > +MediaContext::MediaContext(UniqueFD &&fd) > + : fd_(std::move(fd)) > +{ > +} > + > +/** > + * \brief Bind a V4L2 video device to a media device context > + * \param[in] dev The video device to bind > + * > + * If the MediaContext has been created by a MediaDevice that does > not > + * support multi-context operations, this function is effectively a > nop. > + * > + * \return 0 on success or a negative error code otherwise > + */ > +int MediaContext::bindDevice(V4L2VideoDevice *dev) > +{ > + if (fd_.get() == -1) > + return 0; > + > + return dev->bindContext(fd_.get()); > +} > + > +/** > + * \brief Bind a V4L2 subdevice to a media device context > + * \param[in] dev The subdevice to bind > + * > + * If the MediaContext has been created by a MediaDevice that does > not > + * support multi-context operations, this function is effectively a > nop. > + * > + * \return 0 on success or a negative error code otherwise > + */ > +int MediaContext::bindDevice(V4L2Subdevice *dev) > +{ > + if (fd_.get() == -1) > + return 0; > + > + return dev->bindContext(fd_.get()); > +} > + > /** > * \class MediaDevice > * \brief The MediaDevice represents a Media Controller device with > its full > @@ -603,6 +699,45 @@ int MediaDevice::disableLinks() > * driver unloading for most devices. The media device is passed as > a parameter. > */ > > +/** > + * \brief Create a MediaContext not associated with a media device > context > + * \return A MediaContext to which bindings devices is a nop > + */ > +std::unique_ptr<MediaContext> MediaDevice::createContext() > +{ > + return std::make_unique<MediaContext>(); > +} > + > +/** > + * \brief Create a MediaContext associated with a media device > context > + * > + * Create a MediaContext by opening the media device and create a > media > + * device context using the obtained file descriptor. > + * > + * The open file descriptor is moved to the MediaContext whose > ownership is > + * moved to the caller of this function. > + * > + * \return A MediaContext to which is possible to bind devices to > + */ s/to which is possible to bind devices to/which devices can be bound to/ Otherwise, Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com> > +std::unique_ptr<MediaContext> SharedMediaDevice::createContext() > +{ > + auto fd = UniqueFD(::open(deviceNode_.c_str(), O_RDWR | > O_CLOEXEC)); > + if (!fd.isValid()) { > + int ret = -errno; > + LOG(MediaDevice, Error) > + << "Failed to open media device at " > + << deviceNode_ << ": " << strerror(-ret); > + return {}; > + } > + > + return std::make_unique<MediaContext>(std::move(fd)); > +} > + > +/** > + * \var MediaDevice::deviceNode_ > + * \brief The media device device node path > + */ > + > /** > * \brief Open the media device > *
diff --git a/include/libcamera/internal/media_device.h b/include/libcamera/internal/media_device.h index ea0e9d66009933bbb9613d27423d2f951520c887..2dbfcc447d84bb6a1eee4ed598d22b5cc45adbe9 100644 --- a/include/libcamera/internal/media_device.h +++ b/include/libcamera/internal/media_device.h @@ -21,6 +21,9 @@ namespace libcamera { +class V4L2VideoDevice; +class V4L2Subdevice; + class MediaDeviceFactory { public: @@ -28,6 +31,19 @@ public: createMediaDevice(const std::string &deviceNode); }; +class MediaContext +{ +public: + MediaContext(); + MediaContext(UniqueFD &&fd); + + int bindDevice(V4L2VideoDevice *dev); + int bindDevice(V4L2Subdevice *dev); + +private: + UniqueFD fd_; +}; + class MediaDevice : protected Loggable { public: @@ -63,10 +79,14 @@ public: std::vector<MediaEntity *> locateEntities(unsigned int function); + virtual std::unique_ptr<MediaContext> createContext(); + protected: MediaDevice(const std::string &deviceNode); std::string logPrefix() const override; + std::string deviceNode_; + private: friend class MediaDeviceFactory; @@ -88,7 +108,6 @@ private: int setupLink(const MediaLink *link, unsigned int flags); std::string driver_; - std::string deviceNode_; std::string model_; unsigned int version_; unsigned int hwRevision_; @@ -111,6 +130,8 @@ public: bool lock() override; void unlock() override; + std::unique_ptr<MediaContext> createContext() override; + private: friend class MediaDeviceFactory; diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp index 70d073f964bde0236585de083baca4cd9c30d193..2b7df346ad9916cf22641ea770e0a1507921d89d 100644 --- a/src/libcamera/media_device.cpp +++ b/src/libcamera/media_device.cpp @@ -21,6 +21,9 @@ #include <libcamera/base/log.h> +#include "libcamera/internal/v4l2_subdevice.h" +#include "libcamera/internal/v4l2_videodevice.h" + /** * \file media_device.h * \brief Provide a representation of a Linux kernel Media Controller device @@ -81,6 +84,99 @@ MediaDeviceFactory::createMediaDevice(const std::string &deviceNode) return std::unique_ptr<MediaDevice>(new MediaDevice(deviceNode)); } +/** + * \class MediaContext + * \brief Represents a media device context + * + * A media device context is obtained from a MediaDevice or a SharedMediaDevice + * instance with the MediaDevice::createContext() and + * SharedMediaDevice::createContext() functions. + * + * MediaContext instances obtained from a MediaDevice that does not support + * multi-context operations will not have a valid file descriptor associated as + * the media device they are created from doesn't support multiple open. For + * this reason binding a device to a context that is obtained from a MediaDevice + * is a nop. + * + * MediaContext instances obtained from a SharedMediaDevice that supports + * multi-context operations owns the file descriptor that identifies the media + * context, obtained by opening the media device multiple times and provided to + * the context at creation time. Binding devices to a context obtained from a + * SharedMediaDevice associates the devices to an execution context which + * remains valid until the last bound device stays valid. + * + * Users of this class can bind devices on valid and invalid MultiContext + * instances alike. If the kernel driver supports multi-context operations + * then the device can be opened multiple times and multiple contexts can be + * created to which devices can be bound to. If the kernel driver doesn't + * support multi-context operations then it can be opened a single time only + * and a creating contexts and bindings devices to it is effectively a nop. + */ + +/** + * \brief Constructs a MediaContext not associated to any media device context + * + * Constructs a media device context not associated to any valid media device + * context file descriptor. Binding devices to such media device context + * is effectively a nop. + */ +MediaContext::MediaContext() +{ +} + +/** + * \brief Construct a MediaContext associated to a valid media device context + * \param[in] fd The file descriptor that identifies a media device context + * + * Construct a media device context to which devices can be bound to. + * + * Constructing a MediaContext with an associated valid media device context + * allows to create isolated execution contexts by binding devices to it. + * + * The file descriptor \a fd obtained by opening the media device and that + * identifies the media device context is moved in the newly constructed + * MediaContext which maintains its ownership and automatically closes it at + * destruction time. + */ +MediaContext::MediaContext(UniqueFD &&fd) + : fd_(std::move(fd)) +{ +} + +/** + * \brief Bind a V4L2 video device to a media device context + * \param[in] dev The video device to bind + * + * If the MediaContext has been created by a MediaDevice that does not + * support multi-context operations, this function is effectively a nop. + * + * \return 0 on success or a negative error code otherwise + */ +int MediaContext::bindDevice(V4L2VideoDevice *dev) +{ + if (fd_.get() == -1) + return 0; + + return dev->bindContext(fd_.get()); +} + +/** + * \brief Bind a V4L2 subdevice to a media device context + * \param[in] dev The subdevice to bind + * + * If the MediaContext has been created by a MediaDevice that does not + * support multi-context operations, this function is effectively a nop. + * + * \return 0 on success or a negative error code otherwise + */ +int MediaContext::bindDevice(V4L2Subdevice *dev) +{ + if (fd_.get() == -1) + return 0; + + return dev->bindContext(fd_.get()); +} + /** * \class MediaDevice * \brief The MediaDevice represents a Media Controller device with its full @@ -603,6 +699,45 @@ int MediaDevice::disableLinks() * driver unloading for most devices. The media device is passed as a parameter. */ +/** + * \brief Create a MediaContext not associated with a media device context + * \return A MediaContext to which bindings devices is a nop + */ +std::unique_ptr<MediaContext> MediaDevice::createContext() +{ + return std::make_unique<MediaContext>(); +} + +/** + * \brief Create a MediaContext associated with a media device context + * + * Create a MediaContext by opening the media device and create a media + * device context using the obtained file descriptor. + * + * The open file descriptor is moved to the MediaContext whose ownership is + * moved to the caller of this function. + * + * \return A MediaContext to which is possible to bind devices to + */ +std::unique_ptr<MediaContext> SharedMediaDevice::createContext() +{ + auto fd = UniqueFD(::open(deviceNode_.c_str(), O_RDWR | O_CLOEXEC)); + if (!fd.isValid()) { + int ret = -errno; + LOG(MediaDevice, Error) + << "Failed to open media device at " + << deviceNode_ << ": " << strerror(-ret); + return {}; + } + + return std::make_unique<MediaContext>(std::move(fd)); +} + +/** + * \var MediaDevice::deviceNode_ + * \brief The media device device node path + */ + /** * \brief Open the media device *
Introduce the MediaContext class that represents a media device context to which video devices and subdevices can be bound to. A MediaContext can be created from a MediaDevice (which does not support multi-context) and from SharedMediaDevice (which supports multi-context). Binding devices to a MediaContext created from MediaDevice is a nop, while MediaContext created from SharedMediaDevice perform proper bindings. Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> --- include/libcamera/internal/media_device.h | 23 ++++- src/libcamera/media_device.cpp | 135 ++++++++++++++++++++++++++++++ 2 files changed, 157 insertions(+), 1 deletion(-)