Re: [PATCH v7 1/7] media: add glossary.rst with a glossary of terms used at V4L2 spec

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On 10/10/2017 10:20 AM, Mauro Carvalho Chehab wrote:
> Em Tue, 10 Oct 2017 09:47:13 +0200
> Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> 
>> On 09/28/2017 12:23 AM, Mauro Carvalho Chehab wrote:
>>> Add a glossary of terms for V4L2, as several concepts are complex
>>> enough to cause misunderstandings.
>>>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
>>> ---
>>>  Documentation/media/uapi/v4l/glossary.rst | 136 ++++++++++++++++++++++++++++++
>>>  Documentation/media/uapi/v4l/v4l2.rst     |   1 +
>>>  2 files changed, 137 insertions(+)
>>>  create mode 100644 Documentation/media/uapi/v4l/glossary.rst
>>>
>>> diff --git a/Documentation/media/uapi/v4l/glossary.rst b/Documentation/media/uapi/v4l/glossary.rst
>>> new file mode 100644
>>> index 000000000000..b6767da1a46e
>>> --- /dev/null
>>> +++ b/Documentation/media/uapi/v4l/glossary.rst
>>> @@ -0,0 +1,136 @@
>>> +========
>>> +Glossary
>>> +========
>>> +
>>> +.. note::
>>> +
>>> +   This goal of section is to standardize the terms used within the V4L2
>>> +   documentation. It is written incrementally as they are standardized in
>>> +   the V4L2 documentation. So, it is a Work In Progress.
>>> +
>>> +.. Please keep the glossary entries in alphabetical order
>>> +
>>> +.. glossary::
>>> +
>>> +    Bridge driver
>>> +	The same as V4L2 main driver.  
>>
>> Change this to the more standard phrase:
>>
>> See: V4L2 main driver.
>>
>>> +
>>> +    Device Node
>>> +	A character device node in the file system used to control and do  
>>
>> and -> and/or
>>
>>> +	input/output data transfers from/to a Kernel driver.
>>> +
>>> +    Digital Signal Processor - DSP
>>> +	A specialized microprocessor, with its architecture optimized for
>>> +	the operational needs of digital signal processing.  
>>
>> I'd say 'requirements' instead of 'needs'. I think that's a better term.
>>
>>> +
>>> +    Driver
>>> +	The part of the Linux Kernel that implements support
>>> +	for a hardware component.
>>> +
>>> +    Field-programmable Gate Array - FPGA
>>> +	A field-programmable gate array (FPGA) is an integrated circuit
>>> +	designed to be configured by a customer or a designer after
>>> +	manufacturing.
>>> +
>>> +	See https://en.wikipedia.org/wiki/Field-programmable_gate_array.
>>> +
>>> +    Hardware component
>>> +	A subset of the media hardware. For example an I²C or SPI device,
>>> +	or an IP block inside an SoC or FPGA.
>>> +
>>> +    Image Signal Processor - ISP
>>> +	A specialised processor that implements a set of algorithms for
>>> +	processing image data. ISPs may implement algorithms for lens
>>> +	shading correction, demosaic, scaling and pixel format conversion
>>> +	as well as produce statistics for the use of the control
>>> +	algorithms (e.g. automatic exposure, white balance and focus).
>>> +
>>> +    Inter-Integrated Circuit - I²C
>>> +	A  multi-master, multi-slave, packet switched, single-ended,
>>> +	serial computer bus used to control V4L2 sub-devices.  
>>
>> I'd rephrase this a bit:
>>
>> 	A  multi-master, multi-slave, packet switched, single-ended,
>> 	serial computer bus. Most V4L2 sub-devices are controlled via
>> 	this bus.
>>
>> Your text suggested that i2c is used exclusively for V4L2 subdevs, but
>> of course it is used for many other devices as well.
>>
>>> +
>>> +	See http://www.nxp.com/docs/en/user-guide/UM10204.pdf.
>>> +
>>> +    Integrated circuit - IC
>>> +	A set of electronic circuits on one small flat piece of
>>> +	semiconductor material, normally silicon.
>>> +
>>> +	Also known as chip.  
>>
>> Perhaps add an entry for 'Chip' as well, with a 'See: Integrated circuit' as
>> description? Just to be consistent.
>>
>>> +
>>> +    Intellectual property core - IP core
>>> +	In electronic design a semiconductor intellectual property core,
>>> +	is a reusable unit of logic, cell, or integrated circuit layout
>>> +	design that is the intellectual property of one party.
>>> +	IP cores may be licensed to another party or can be owned
>>> +	and used by a single party alone.
>>> +
>>> +	See https://en.wikipedia.org/wiki/Semiconductor_intellectual_property_core).
>>> +
>>> +    IP block
>>> +	The same as IP core.  
>>
>> 'See: '
>>
>>> +
>>> +    MC-centric
>>> +	V4L2 hardware that requires a Media controller.
>>> +
>>> +	See :ref:`v4l2_hardware_control`.
>>> +
>>> +    Media Controller
>>> +	An API designed to expose and control devices and sub-devices
>>> +	relationships to applications.  
>>
>> This sentence is not clear. I propose this:
>>
>> 	An API designed to expose and control the relationships of the Media
>> 	Harware to applications.
>>
>>> +
>>> +	See :ref:`media_controller`.
>>> +
>>> +    Media hardware
>>> +	A group of hardware components that together make a larger
>>> +	user-facing functional media hardware. For instance the SoC ISP IP  
>>
>> I'd just say "form the functional". The term 'user-facing' is out of place here.
>>
>>> +	cores and external camera sensors together make a  
>>
>> make a -> form the
>>
>> Possible synonym for 'form': 'constitute'. I'm OK with either.
>>
>>> +	camera media hardware.
>>> +
>>> +    Media hardware control
>>> +	Type of control for a media hardware supported by V4L2 drivers.
>>> +
>>> +	See :ref:`v4l2_hardware_control`.
>>> +
>>> +    Microprocessor
>>> +	An electronic circuitry that carries out the instructions
>>> +	of a computer program by performing the basic arithmetic, logical,
>>> +	control and input/output (I/O) operations specified by the
>>> +	instructions on a single integrated circuit.
>>> +
>>> +    SMBus
>>> +	A subset of I²C, with defines a stricter usage of the bus.
>>> +
>>> +    Serial Peripheral Interface Bus - SPI
>>> +	Synchronous serial communication interface specification used for
>>> +	short distance communication, primarily in embedded systems.
>>> +
>>> +    System on a Chip - SoC
>>> +	An integrated circuit that integrates all components of a computer
>>> +	or other electronic systems.
>>> +
>>> +    V4L2 device node
>>> +	A device node that is associated to a V4L2 main driver,
>>> +	as specified in :ref:`v4l2_device_naming`.
>>> +
>>> +    V4L2 hardware
>>> +	A hardware used to on a media device supported by the V4L2
>>> +	subsystem.  
>>
>> No idea what you mean here. Perhaps this:
>>
>> Hardware that is controlled by a V4L2 main driver or a V4L2 sub-device driver.
>> V4L2 hardware is a subset of the Media hardware. Often the two are the same,
>> but Media hardware can also contain other non-V4L2 hardware such as DVB hardware.
>>
>>> +
>>> +    V4L2 main driver
>>> +	The V4L2 device driver that implements the main logic to talk with
>>> +	the V4L2 hardware.
>>> +
>>> +	Also known as bridge driver.
>>> +
>>> +	See :ref:`v4l2_hardware_control`.
>>> +
>>> +    V4L2 sub-device
>>> +	Part of the media hardware that is implemented via a
>>> +	V4L2 sub-device driver.  
>>
>> When we talk about 'V4L2 sub-device' we talk about a driver that implement
>> the subdev kernel API. I suggest that you change 'V4L2 sub-device' to
>> 'V4L2 sub-device driver', then explain that such a driver implements support
>> for a Hardware component.
>>
>>> +
>>> +	See :ref:`subdev`.
>>> +
>>> +    Vdevnode-centric
>>> +	V4L2 hardware that it is controlled via V4L2 device nodes.  
>>
>> 'that it' -> 'that'
>>
>> This also needs a reference:
>>
>> 	See :ref:`v4l2_hardware_control`.
>>
>>> +
>>> +	See :ref:`v4l2_hardware_control`.
>>> diff --git a/Documentation/media/uapi/v4l/v4l2.rst b/Documentation/media/uapi/v4l/v4l2.rst
>>> index 2128717299b3..698c060939f0 100644
>>> --- a/Documentation/media/uapi/v4l/v4l2.rst
>>> +++ b/Documentation/media/uapi/v4l/v4l2.rst
>>> @@ -32,6 +32,7 @@ This part describes the Video for Linux API version 2 (V4L2 API) specification.
>>>      videodev
>>>      capture-example
>>>      v4l2grab-example
>>> +    glossary
>>>      biblio
>>>  
>>>  
>>>   
>>
>> Regards,
>>
>> 	Hans
> 
> I agree with all proposed changes. I'm folding the attached patch to it.
> 
> Thanks,
> Mauro
> 
> diff --git a/Documentation/media/uapi/v4l/glossary.rst b/Documentation/media/uapi/v4l/glossary.rst
> index b6767da1a46e..e95820d91bac 100644
> --- a/Documentation/media/uapi/v4l/glossary.rst
> +++ b/Documentation/media/uapi/v4l/glossary.rst
> @@ -13,15 +13,18 @@ Glossary
>  .. glossary::
>  
>      Bridge driver
> -	The same as V4L2 main driver.
> +	See: V4L2 main driver.
> +
> +    Chip:
> +	See: Integrated circuit.
>  
>      Device Node
> -	A character device node in the file system used to control and do
> -	input/output data transfers from/to a Kernel driver.
> +	A character device node in the file system used to control and/or
> +	do input/output data transfers from/to a Kernel driver.
>  
>      Digital Signal Processor - DSP
>  	A specialized microprocessor, with its architecture optimized for
> -	the operational needs of digital signal processing.
> +	the operational requirements of digital signal processing.
>  
>      Driver
>  	The part of the Linux Kernel that implements support
> @@ -47,7 +50,8 @@ Glossary
>  
>      Inter-Integrated Circuit - I²C
>  	A  multi-master, multi-slave, packet switched, single-ended,
> -	serial computer bus used to control V4L2 sub-devices.
> +	serial computer bus. Most V4L2 sub-device are controlled
> +	via this bus.
>  
>  	See http://www.nxp.com/docs/en/user-guide/UM10204.pdf.
>  
> @@ -67,7 +71,7 @@ Glossary
>  	See https://en.wikipedia.org/wiki/Semiconductor_intellectual_property_core).
>  
>      IP block
> -	The same as IP core.
> +	See: IP core.
>  
>      MC-centric
>  	V4L2 hardware that requires a Media controller.
> @@ -75,15 +79,15 @@ Glossary
>  	See :ref:`v4l2_hardware_control`.
>  
>      Media Controller
> -	An API designed to expose and control devices and sub-devices
> -	relationships to applications.
> +	An API designed to expose and control the relationships of the Media
> +	Harware to applications.
>  
>  	See :ref:`media_controller`.
>  
>      Media hardware
> -	A group of hardware components that together make a larger
> -	user-facing functional media hardware. For instance the SoC ISP IP
> -	cores and external camera sensors together make a
> +	A group of hardware components that together form the
> +	functional media hardware. For instance the SoC ISP IP
> +	cores and external camera sensors together form the
>  	camera media hardware.
>  
>      Media hardware control
> @@ -113,8 +117,10 @@ Glossary
>  	as specified in :ref:`v4l2_device_naming`.
>  
>      V4L2 hardware
> -	A hardware used to on a media device supported by the V4L2
> -	subsystem.
> +	Hardware that is controlled by a V4L2 main driver or a V4L2
> +	sub-device driver. V4L2 hardware is a subset of the
> +	Media hardware. Often the two are the same, but Media hardware
> +	can also contain other non-V4L2 hardware such as DVB hardware.
>  
>      V4L2 main driver
>  	The V4L2 device driver that implements the main logic to talk with
> @@ -125,12 +131,15 @@ Glossary
>  	See :ref:`v4l2_hardware_control`.
>  
>      V4L2 sub-device
> -	Part of the media hardware that is implemented via a
> -	V4L2 sub-device driver.
> +	See: :ref:`V4L2 sub-device driver`
> +
> +    V4L2 sub-device driver
> +	Part of the media hardware that implements support for
> +	a hardware component.

The description now no longer fits the term. I suggest:

"The V4L2 driver that implements support for a hardware component."

Otherwise this looks good.

Regards,

	Hans

>  
>  	See :ref:`subdev`.
>  
>      Vdevnode-centric
> -	V4L2 hardware that it is controlled via V4L2 device nodes.
> +	V4L2 hardware that is controlled via V4L2 device nodes.
>  
>  	See :ref:`v4l2_hardware_control`.
> 
> 

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