[libcamera-devel] [PATCH v5 2/6] libcamera: v4l2_device: List valid controls at open

[Jacopo Mondi]

Hi Laurent,

On Sat, Jun 22, 2019 at 08:16:52PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Thu, Jun 20, 2019 at 05:31:40PM +0200, Jacopo Mondi wrote:
> > Enumerate all the valid controls a device supports at open() time.
> > A control is valid only if its type is supported.
> >
> > Store the control informations in a map inside the device to save
>
> s/informations/information/
>
> https://en.wiktionary.org/wiki/informations
>
> "Most senses of the word “information” are uncountable. The legal sense,
> referring to court filings, is one that does form a plural."
>
> > querying the control when setting or getting its value from the device
> > and provide an operation to retrieve information by control ID.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> >  src/libcamera/include/v4l2_device.h |  9 ++++
> >  src/libcamera/v4l2_device.cpp       | 72 +++++++++++++++++++++++++++++
> >  2 files changed, 81 insertions(+)
> >
> > diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
> > index 75f23a05b903..91a72fcecbcc 100644
> > --- a/src/libcamera/include/v4l2_device.h
> > +++ b/src/libcamera/include/v4l2_device.h
> > @@ -7,18 +7,23 @@
> >  #ifndef __LIBCAMERA_V4L2_DEVICE_H__
> >  #define __LIBCAMERA_V4L2_DEVICE_H__
> >
> > +#include <map>
> >  #include <string>
> >
> >  #include "log.h"
> >
> >  namespace libcamera {
> >
> > +class V4L2ControlInfo;
> > +
> >  class V4L2Device : protected Loggable
> >  {
> >  public:
> >  	void close();
> >  	bool isOpen() const { return fd_ != -1; }
> >
> > +	const V4L2ControlInfo *getControlInfo(unsigned int id) const;
> > +
> >  	const std::string &deviceNode() const { return deviceNode_; }
> >
> >  protected:
> > @@ -32,6 +37,10 @@ protected:
> >  	int fd() { return fd_; }
> >
> >  private:
> > +	void listControls();
> > +	int validateControlType(const V4L2ControlInfo *info);
> > +
> > +	std::map<unsigned int, V4L2ControlInfo> controls_;
> >  	std::string deviceNode_;
> >  	int fd_;
> >  };
> > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > index 99621a724b96..b113ff77e3cf 100644
> > --- a/src/libcamera/v4l2_device.cpp
> > +++ b/src/libcamera/v4l2_device.cpp
> > @@ -13,6 +13,7 @@
> >  #include <unistd.h>
> >
> >  #include "log.h"
> > +#include "v4l2_controls.h"
> >
> >  /**
> >   * \file v4l2_device.h
> > @@ -82,6 +83,8 @@ int V4L2Device::open(unsigned int flags)
> >
> >  	fd_ = ret;
> >
> > +	listControls();
> > +
> >  	return 0;
> >  }
> >
> > @@ -107,6 +110,21 @@ void V4L2Device::close()
> >   * \return True if the V4L2 device node is open, false otherwise
> >   */
> >
> > +/**
> > + * \brief Retrieve information about a control
> > + * \param[in] id The control ID
> > + * \return A pointer to the V4L2ControlInfo for control \a id, or nullptr
> > + * if the device doesn't have such a control
> > + */
> > +const V4L2ControlInfo *V4L2Device::getControlInfo(unsigned int id) const
> > +{
> > +	auto it = controls_.find(id);
> > +	if (it == controls_.end())
> > +		return nullptr;
> > +
> > +	return &it->second;
> > +}
> > +
> >  /**
> >   * \brief Perform an IOCTL system call on the device node
> >   * \param[in] request The IOCTL request code
> > @@ -137,4 +155,58 @@ int V4L2Device::ioctl(unsigned long request, void *argp)
> >   * \return The V4L2 device file descriptor, -1 if the device node is not open
> >   */
> >
> > +/*
> > + * \brief List and store information about all controls supported by the
> > + * V4L2 device
> > + */
> > +void V4L2Device::listControls()
> > +{
> > +	struct v4l2_query_ext_ctrl ctrl = {};
> > +
> > +	/* \todo Add support for menu and compound controls. */
> > +	ctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
> > +	while (ioctl(VIDIOC_QUERY_EXT_CTRL, &ctrl) == 0) {
> > +		if (ctrl.type == V4L2_CTRL_TYPE_CTRL_CLASS ||
> > +		    ctrl.flags & V4L2_CTRL_FLAG_DISABLED) {
> > +			ctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
> > +			continue;
> > +		}
> > +
> > +		V4L2ControlInfo info(ctrl);
> > +		if (validateControlType(&info))
> > +			continue;
> > +
> > +		controls_.insert(std::pair<unsigned int, V4L2ControlInfo>
> > +				 (ctrl.id, info));
>
> Anything wrong with
>
> 		controls_[ctrl.id] = info;
>
> ?

No, I could change it. I used std::vector::insert when I was
constructing the V4L2ControlInfo directly in the operation call, it's
a leftover.

>
> > +		ctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
> > +	}
> > +}
> > +
> > +/*
> > + * \brief Make sure the control type is supported
> > + * \param[in] info The V4L2ControlInfo to inspect type of
> > + * \return 0 on success or a negative error code otherwise
> > + * \retval -EINVAL The control type is not supported
> > + */
> > +int V4L2Device::validateControlType(const V4L2ControlInfo *info)
>
> As this method has a single user, how about inlining it ?
> V4L2Device::listControls() isn't big.
>

I would rather keep the type validation centralized in one place, and in
the caller it's easy enough to parse if (validateControlType(type))
for a reader than going through the switch cases.

The cost of a function call is negligible considering this happens
only at device open time.

Thanks
  j

> > +{
> > +	/* \todo Support compound controls. */
> > +	switch (info->type()) {
> > +	case V4L2_CTRL_TYPE_INTEGER:
> > +	case V4L2_CTRL_TYPE_BOOLEAN:
> > +	case V4L2_CTRL_TYPE_MENU:
> > +	case V4L2_CTRL_TYPE_BUTTON:
> > +	case V4L2_CTRL_TYPE_INTEGER64:
> > +	case V4L2_CTRL_TYPE_BITMASK:
> > +	case V4L2_CTRL_TYPE_INTEGER_MENU:
> > +		break;
> > +	default:
> > +		LOG(V4L2, Error) << "Control type '" << info->type()
> > +				 << "' not supported";
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  } /* namespace libcamera */
>
> --
> Regards,
>
> Laurent Pinchart
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