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 âSoftware 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(-)
>
>
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