[libcamera-devel] [PATCH v2 04/10] libcamera: ipa_module: allow instantiation of IPAInterface

[Laurent Pinchart]

Hi Paul,

Thank you for the patch.

On Mon, Jun 03, 2019 at 07:16:31PM -0400, Paul Elder wrote:
> Add functions for loading the IPAInterface factory function from an IPA
> module shared object, and for creating an instance of an IPAInterface.
> These functions will be used by IPAManager, from which a PipelineHandler
> will request an IPAInterface.
> 
> Also update meson to add the "-ldl" linker argument, to allow loading of
> the factory function from a shared object.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> ---
> Changes in v2:
> - mostly just documentation
> 
>  src/libcamera/include/ipa_module.h | 12 +++++
>  src/libcamera/ipa_module.cpp       | 83 ++++++++++++++++++++++++++++--
>  src/libcamera/meson.build          |  3 +-
>  3 files changed, 94 insertions(+), 4 deletions(-)
> 
> diff --git a/src/libcamera/include/ipa_module.h b/src/libcamera/include/ipa_module.h
> index a4c6dbd..557435c 100644
> --- a/src/libcamera/include/ipa_module.h
> +++ b/src/libcamera/include/ipa_module.h
> @@ -7,8 +7,10 @@
>  #ifndef __LIBCAMERA_IPA_MODULE_H__
>  #define __LIBCAMERA_IPA_MODULE_H__
>  
> +#include <memory>
>  #include <string>
>  
> +#include <libcamera/ipa/ipa_interface.h>
>  #include <libcamera/ipa/ipa_module_info.h>
>  
>  namespace libcamera {
> @@ -17,16 +19,26 @@ class IPAModule
>  {
>  public:
>  	explicit IPAModule(const std::string &libPath);
> +	~IPAModule();
>  
>  	bool isValid() const;
>  
>  	const struct IPAModuleInfo &info() const;
>  
> +	bool load();
> +
> +	std::unique_ptr<IPAInterface> createInstance();
> +
>  private:
>  	struct IPAModuleInfo info_;
>  
>  	std::string libPath_;
>  	bool valid_;
> +	bool loaded_;
> +
> +	void *dlHandle_;
> +	typedef IPAInterface *(*ipaIntfFactory)(void);

This is a type so it should start with an uppercase letter. Furthermore,
as the type name is defined in the context of the IPAModule class, it
doesn't have to start with IPA. How about just FactoryFunction ?

> +	ipaIntfFactory ipaCreate_;
>  
>  	int loadIPAModuleInfo();
>  };
> diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp
> index 067f868..91d97ae 100644
> --- a/src/libcamera/ipa_module.cpp
> +++ b/src/libcamera/ipa_module.cpp
> @@ -7,6 +7,7 @@
>  
>  #include "ipa_module.h"
>  
> +#include <dlfcn.h>
>  #include <elf.h>
>  #include <errno.h>
>  #include <fcntl.h>
> @@ -257,13 +258,12 @@ int elfLoadSymbol(void *dst, size_t size, void *map, size_t soSize,
>   * The IPA module shared object file must be of the same endianness and
>   * bitness as libcamera.
>   *
> - * \todo load funtions from the IPA to be used by pipelines
> - *
>   * The caller shall call the isValid() method after constructing an
>   * IPAModule instance to verify the validity of the IPAModule.
>   */
>  IPAModule::IPAModule(const std::string &libPath)
> -	: libPath_(libPath), valid_(false)
> +	: libPath_(libPath), valid_(false), loaded_(false),
> +	  dlHandle_(nullptr), ipaCreate_(nullptr)
>  {
>  	if (loadIPAModuleInfo() < 0)
>  		return;
> @@ -271,6 +271,12 @@ IPAModule::IPAModule(const std::string &libPath)
>  	valid_ = true;
>  }
>  
> +IPAModule::~IPAModule()
> +{
> +	if (dlHandle_)
> +		dlclose(dlHandle_);
> +}
> +
>  int IPAModule::loadIPAModuleInfo()
>  {
>  	int fd = open(libPath_.c_str(), O_RDONLY);
> @@ -340,4 +346,75 @@ const struct IPAModuleInfo &IPAModule::info() const
>  	return info_;
>  }
>  
> +/**
> + * \brief Load the IPA implementation factory from the shared object
> + *
> + * The IPA module shared object implements an IPAInterface class to be used
> + * by pipeline handlers. This function loads the factory function from the

s/This function/This method/

("factory function" is correct as it's a pure C function)

> + * shared object. Later, createInstance() can be called to instantiate the
> + * IPAInterface.
> + *
> + * This method only needs to be called successfully once, after which
> + * createInstance can be called as many times as IPAInterface instances are

createInstance()

> + * needed.
> + *
> + * Calling this function on an invalid module (as returned by isValid()) is
> + * an error.
> + *
> + * \return true if load was successful, or already loaded, and false otherwise

s/true/True/

> + */
> +bool IPAModule::load()
> +{
> +	if (!valid_)
> +		return false;
> +
> +	if (loaded_)
> +		return true;
> +
> +	dlHandle_ = dlopen(libPath_.c_str(), RTLD_LAZY);
> +	if (!dlHandle_) {
> +		LOG(IPAModule, Error)
> +			<< "Failed to open IPA module shared object "

s/object/object:/

> +			<< dlerror();
> +		return false;
> +	}
> +
> +	void *symbol = dlsym(dlHandle_, "ipaCreate");
> +	if (!symbol) {
> +		LOG(IPAModule, Error)
> +			<< "Failed to load ipaCreate() from IPA module shared object "

s/object/object:/

> +			<< dlerror();
> +		dlclose(dlHandle_);
> +		dlHandle_ = nullptr;
> +		return false;
> +	}
> +
> +	ipaCreate_ = (ipaIntfFactory)symbol;

Let's use C++-style casts.

	ipaCreate_ = reinterpret_cast<ipaIntfFactory>(symbol);

> +
> +	loaded_ = true;
> +
> +	return true;
> +}
> +
> +/**
> + * \brief Instantiate an IPAInterface
> + *
> + * After loading the IPA module with load(), this method creates an
> + * instance of the IPA module interface.
> + *
> + * Calling this function on a module that has not yet been loaded, or an
> + * invalid module (as returned by load() and isValid(), respectively) is
> + * an error.
> + *
> + * \return the IPA implementation as a new IPAInterface instance on success,

s/the/The/

With those small issues fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> + * or nullptr on error
> + */
> +std::unique_ptr<IPAInterface> IPAModule::createInstance()
> +{
> +	if (!valid_ || !loaded_)
> +		return nullptr;
> +
> +	return std::unique_ptr<IPAInterface>(ipaCreate_());
> +}
> +
>  } /* namespace libcamera */
> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> index 07335e5..32f7da4 100644
> --- a/src/libcamera/meson.build
> +++ b/src/libcamera/meson.build
> @@ -65,7 +65,8 @@ libcamera = shared_library('camera',
>                             libcamera_sources,
>                             install : true,
>                             include_directories : includes,
> -                           dependencies : libudev)
> +                           dependencies : libudev,
> +                           link_args : '-ldl')
>  
>  libcamera_dep = declare_dependency(sources : [libcamera_api, libcamera_h],
>                                     include_directories : libcamera_includes,

-- 
Regards,

Laurent Pinchart