Hi Mauro, On Sat April 20 2013 19:51:11 Mauro Carvalho Chehab wrote: > This is a version 2 of the V4L2 API bits to support Software Digital > Radio (SDR). It looks pretty good to me. Just one question though: what is your rationale for choosing a new device name (/dev/sdrX) instead of using the existing /dev/radioX? I'm not saying I'm opposed to it, in fact I agree with it, but I think the reasons for it should be stated explicitly. Regards, Hans > > > The changes from version 1 are: > - fix compilation; > - add a new capture type for SDR (V4L2_BUF_TYPE_SDR_CAPTURE), > with the corresponding documentation; > - remove legacy V4L1 buffer types from videobuf2.h. > > With regards to VIDIOC_S_TUNER, what's currently defined there is > that, in contrary to what a radio device does, this ioctl would > set the input. > > This patch adds the very basic stuff for SDR: > > - a separate devnode; > - an VIDIOC_QUERYCAP caps for SDR; > - a fourcc group for SDR; > - a few DocBook bits. > > What's missing: > - SDR specific controls; > - Sample rate config; > ... > > As discussing DocBook changes inside the patch is hard, I'm adding here > the DocBook formatted changes. > > The DocBook changes add the following bits: > > At Chapter 1. Common API Elements, it adds: > > <text> > Software Digital Radio (SDR) Tuners and Modulators > ================================================== > > Those devices are special types of Radio devices that don't have any > analog demodulator. Instead, it samples the radio IF or baseband and > sends the samples for userspace to demodulate. > > Tuners > ====== > > SDR receivers can have one or more tuners sampling RF signals. Each > tuner is associated with one or more inputs, depending on the number of > RF connectors on the tuner. The type field of the respective struct > v4l2_input returned by the VIDIOC_ENUMINPUT ioctl is set to > V4L2_INPUT_TYPE_TUNER and its tuner field contains the index number of > the tuner input. > > To query and change tuner properties applications use the VIDIOC_G_TUNER > and VIDIOC_S_TUNER ioctl, respectively. The struct v4l2_tuner returned > by VIDIOC_G_TUNER also contains signal status information applicable > when the tuner of the current SDR input is queried. In order to change > the SDR input, VIDIOC_S_TUNER with a new SDR index should be called. > Drivers must support both ioctls and set the V4L2_CAP_SDR and > V4L2_CAP_TUNER flags in the struct v4l2_capability returned by the > VIDIOC_QUERYCAP ioctl. > > Modulators > ========== > > To be defined. > </text> > > At the end of Chapter 2. Image Formats, it adds: > > <text> > SDR format struture > =================== > > Table 2.4. struct v4l2_sdr_format > ================================= > > __u32 sampleformat The format of the samples used by the SDR device. > This is a little endian four character code. > > Table 2.5. SDR formats > ====================== > > V4L2_SDR_FMT_I8Q8 Samples are given by a sequence of 8 bits in-phase(I) > and 8 bits quadrature (Q) samples taken from a > signal(t) represented by the following expression: > signal(t) = I * cos(2Ï? fc t) - Q * sin(2Ï? fc t) > </text> > > Of course, other formats will be needed at Table 2.5, as SDR could also > be taken baseband samples, being, for example, a simple sequence of > equally time-spaced digitalized samples of the signal in time. > SDR samples could also use other resolutions, use a non-linear > (A-law, u-law) ADC, or even compress the samples (with ADPCM, for > example). So, this table will grow as newer devices get added, and an > userspace library may be required to convert them into some common > format. > > At "Chapter 4. Interfaces", it adds the following text: > > <text> > Software Digital Radio(SDR) Interface > ===================================== > > This interface is intended for Software Digital Radio (SDR) receivers > and transmitters. > > Conventionally V4L2 SDR devices are accessed through character device > special files named /dev/sdr0 to/dev/radio255 and uses a dynamically > allocated major/minor number. > > Querying Capabilities > ===================== > > Devices supporting the radio interface set the V4L2_CAP_SDR and > V4L2_CAP_TUNER or V4L2_CAP_MODULATOR flag in the capabilities field of > struct v4l2_capability returned by the VIDIOC_QUERYCAP ioctl. Other > combinations of capability flags are reserved for future extensions. > > Supplemental Functions > ====================== > > SDR receivers should support tuner ioctls. > > SDR transmitter ioctl's will be defined in the future. > > SDR devices should also support one or more of the following I/O ioctls: > read or write, memory mapped IO, user memory IO and/or DMA buffers. > > SDR devices can also support controls ioctls. > > The SDR Input/Output are A/D or D/A samples taken from a modulated > signal, and can eventually be packed by the hardware. They are generally > encoded using cartesian in-phase/quadrature (I/Q) samples, to make > demodulation easier. The format of the samples should be according with > SDR format. > </text> > > Note: "SDR format" on the last paragraph is an hyperlink to > Chapter 2. Image Formats. > > At "Appendix A. Function Reference - ioctl VIDIOC_QUERYCAP", it adds: > > <text> > Table A.93. Device Capabilities Flags > ... > V4L2_CAP_SDR 0x00100000 The device is a Software Digital Radio. > For more information about SDR programming > see the section called â??Software Digital > Radio (SDR) Tuners and Modulatorsâ??. > </text> > > Mauro Carvalho Chehab (3): > [media] Add SDR at V4L2 API > videodev2.h: Remove the unused old V4L1 buffer types > [media] V4L2 api: Add a buffer capture type for SDR > > Documentation/DocBook/media/v4l/common.xml | 35 ++++++++++++++++++ > Documentation/DocBook/media/v4l/dev-capture.xml | 26 ++++++++------ > Documentation/DocBook/media/v4l/io.xml | 6 ++++ > Documentation/DocBook/media/v4l/pixfmt.xml | 41 ++++++++++++++++++++++ > Documentation/DocBook/media/v4l/v4l2.xml | 1 + > .../DocBook/media/v4l/vidioc-querycap.xml | 7 ++++ > drivers/media/v4l2-core/v4l2-dev.c | 3 ++ > drivers/media/v4l2-core/v4l2-ioctl.c | 32 +++++++++++++++++ > include/media/v4l2-dev.h | 3 +- > include/media/v4l2-ioctl.h | 8 +++++ > include/uapi/linux/videodev2.h | 33 +++++++---------- > 11 files changed, 163 insertions(+), 32 deletions(-) > > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
