document types of hardware control for V4L2
Subsystems (2)
v2 cover document types of hardware control for V4L2
On 2010, we introduced a new way to control complex V4L2 devices used on embedded systems, but this was never documented, nor it is possible for an userspace applicatin to detect the kind of control a device supports.
This series fill the gap.
Mauro Carvalho Chehab (3):
media: open.rst: better document device node naming
media: open.rst: document devnode-centric and mc-centric types
media: videodev2: add a flag for MC-centric devices
-
v2:
- added a patch at the beginning of the series better defining the device node naming rules;
- better defined the differenes between device hardware and V4L2 device node as suggested by Laurent and with changes proposed by Hans and Sakari
- changed the caps flag to indicate MC-centric devices
- removed the final patch that would use the new caps flag. I'll write it once we agree on the new caps flag.
Documentation/media/uapi/v4l/open.rst | 104 +++++++++++++++++++++-- Documentation/media/uapi/v4l/vidioc-querycap.rst | 5 ++ include/uapi/linux/videodev2.h | 2 + 3 files changed, 106 insertions(+), 5 deletions(-)
Signature · 1 line
2.13.3
PATCH v2 1/3 media: open.rst: better document device node naming
Right now, only kAPI documentation describes the device naming. However, such description is needed at the uAPI too. Add it, and describe how to get an unique identify for a given device.
--- Documentation/media/uapi/v4l/open.rst | 40 ++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)
Documentation/media/uapi/v4l/open.rst +35 -5
@@ -7,12 +7,12 @@ Opening and Closing Devices *************************** -Device Naming -============= +V4L2 Device Node Naming +======================= V4L2 drivers are implemented as kernel modules, loaded manually by the system administrator or automatically when a device is first discovered. -The driver modules plug into the "videodev" kernel module. It provides +The driver modules plug into the ``videodev`` kernel module. It provides helper functions and a common application interface specified in this document.
@@ -20,8 +20,38 @@ Each driver thus loaded registers one or more device nodes with major number 81 and a minor number between 0 and 255. Minor numbers are allocated dynamically unless the kernel is compiled with the kernel option CONFIG_VIDEO_FIXED_MINOR_RANGES. In that case minor numbers -are allocated in ranges depending on the device node type (video, radio, -etc.). +are allocated in ranges depending on the device node type. + +The existing V4L2 device node types are: + +======================== ====================================================== +Default device node name Usage +======================== ====================================================== +``/dev/videoX`` Video input/output devices +``/dev/vbiX`` Vertical blank data (i.e. closed captions, teletext) +``/dev/radioX`` Radio tuners +``/dev/swradioX`` Software Defined Radio tuners +``/dev/v4l-touchX`` Touch sensors +======================== ====================================================== + +Where ``X`` is a non-negative number. + +.. note:: + + 1. The actual device node name is system-dependent, as udev rules may apply. + 2. There's not warranty that ``X`` will remain the same for the same + device, as the number depends on the device driver's probe order. + If you need an unique name, udev default rules produce + ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` that can use to uniquelly + identify a V4L2 device node:: + + $ tree /dev/v4l + /dev/v4l + ├── by-id + │ └── usb-OmniVision._USB_Camera-B4.04.27.1-video-index0 -> ../../video0 + └── by-path + └── pci-0000:00:14.0-usb-0:2:1.0-video-index0 -> ../../video0 + Many drivers support "video_nr", "radio_nr" or "vbi_nr" module options to select specific video/radio/vbi node numbers. This allows the
Signature · 1 line
2.13.3
Re: [PATCH v2 1/3] media: open.rst: better document device node naming
Em Fri, 25 Aug 2017 09:52:40 -0300
Mauro Carvalho Chehab <[email protected]> escreveu:
Quoted 50 lines
Right now, only kAPI documentation describes the device naming. However, such description is needed at the uAPI too. Add it, and describe how to get an unique identify for a given device.
Signed-off-by Mauro Carvalho Chehab <[email protected]>--- Documentation/media/uapi/v4l/open.rst | 40 ++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)Documentation/media/uapi/v4l/open.rst +18
-5@@ -7,12 +7,12 @@ Opening and Closing Devices *************************** -Device Naming -============= +V4L2 Device Node Naming +======================= V4L2 drivers are implemented as kernel modules, loaded manually by the system administrator or automatically when a device is first discovered. -The driver modules plug into the "videodev" kernel module. It provides +The driver modules plug into the ``videodev`` kernel module. It provides helper functions and a common application interface specified in this document.@@ -20,8 +20,38 @@ Each driver thus loaded registers one or more device nodes with major number 81 and a minor number between 0 and 255. Minor numbers are allocated dynamically unless the kernel is compiled with the kernel option CONFIG_VIDEO_FIXED_MINOR_RANGES. In that case minor numbers -are allocated in ranges depending on the device node type (video, radio, -etc.). +are allocated in ranges depending on the device node type. + +The existing V4L2 device node types are: + +======================== ====================================================== +Default device node name Usage +======================== ====================================================== +``/dev/videoX`` Video input/output devices +``/dev/vbiX`` Vertical blank data (i.e. closed captions, teletext) +``/dev/radioX`` Radio tuners +``/dev/swradioX`` Software Defined Radio tuners +``/dev/v4l-touchX`` Touch sensors +======================== ====================================================== + +Where ``X`` is a non-negative number.
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 47
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +10
-0+ +.. note:: + + 1. The actual device node name is system-dependent, as udev rules may apply. + 2. There's not warranty that ``X`` will remain the same for the same + device, as the number depends on the device driver's probe order. + If you need an unique name, udev default rules produce + ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` that can use to uniquelly + identify a V4L2 device node:: +
In time:
Documentation/media/uapi/v4l/open.rst +2 -2
@@ -106,8 +106,8 @@ Where ``X`` is a non-negative number. 2. There's not warranty that ``X`` will remain the same for the same device, as the number depends on the device driver's probe order. If you need an unique name, udev default rules produce - ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` that can use to uniquelly - identify a V4L2 device node:: + ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` that can be used to + uniquely identify a V4L2 device node:: $ tree /dev/v4l /dev/v4l
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 57
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +7
-0+ $ tree /dev/v4l + /dev/v4l + ├── by-id + │ └── usb-OmniVision._USB_Camera-B4.04.27.1-video-index0 -> ../../video0 + └── by-path + └── pci-0000:00:14.0-usb-0:2:1.0-video-index0 -> ../../video0 + Many drivers support "video_nr", "radio_nr" or "vbi_nr" module options to select specific video/radio/vbi node numbers. This allows the
Thanks,
Mauro
Re: [PATCH v2 1/3] media: open.rst: better document device node naming
In reply to Mauro Carvalho ChehabQuoted 35 lines · Mauro Carvalho Chehab
Right now, only kAPI documentation describes the device naming. However, such description is needed at the uAPI too. Add it, and describe how to get an unique identify for a given device.
Signed-off-by Mauro Carvalho Chehab <[email protected]>--- Documentation/media/uapi/v4l/open.rst | 40 ++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)Documentation/media/uapi/v4l/open.rst +3
-5@@ -7,12 +7,12 @@ Opening and Closing Devices *************************** -Device Naming -============= +V4L2 Device Node Naming +======================= V4L2 drivers are implemented as kernel modules, loaded manually by the system administrator or automatically when a device is first discovered. -The driver modules plug into the "videodev" kernel module. It provides +The driver modules plug into the ``videodev`` kernel module. It provides helper functions and a common application interface specified in this document.@@ -20,8 +20,38 @@ Each driver thus loaded registers one or more device nodes with major number 81 and a minor number between 0 and 255. Minor numbers are allocated dynamically unless the kernel is compiled with the kernel option CONFIG_VIDEO_FIXED_MINOR_RANGES. In that case minor numbers -are allocated in ranges depending on the device node type (video, radio, -etc.).
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 32
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +10
-0+are allocated in ranges depending on the device node type. + +The existing V4L2 device node types are: + +======================== ====================================================== +Default device node name Usage +======================== ====================================================== +``/dev/videoX`` Video input/output devices +``/dev/vbiX`` Vertical blank data (i.e. closed captions, teletext) +``/dev/radioX`` Radio tuners
add: and modulators.
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 33
Quoted 1 line
Documentation/media/uapi/v4l/open.rst +1
-0+``/dev/swradioX`` Software Defined Radio tuners
Ditto.
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 42
Quoted 9 lines
Documentation/media/uapi/v4l/open.rst +9
-0+``/dev/v4l-touchX`` Touch sensors +======================== ====================================================== + +Where ``X`` is a non-negative number. + +.. note:: + + 1. The actual device node name is system-dependent, as udev rules may apply. + 2. There's not warranty that ``X`` will remain the same for the same
"There is no"
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 45
Quoted 3 lines
Documentation/media/uapi/v4l/open.rst +3
-0+ device, as the number depends on the device driver's probe order. + If you need an unique name, udev default rules produce + ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` that can use to uniquelly
``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` directories containing links
that be can used to uniquely
Documentation/media/uapi/v4l/open.rst Each driver thus loaded registers one or more device nodes with major · line 57
Quoted 13 lines
Documentation/media/uapi/v4l/open.rst +9
-0+ identify a V4L2 device node:: + + $ tree /dev/v4l + /dev/v4l + ├── by-id + │ └── usb-OmniVision._USB_Camera-B4.04.27.1-video-index0 -> ../../video0 + └── by-path + └── pci-0000:00:14.0-usb-0:2:1.0-video-index0 -> ../../video0 + Many drivers support "video_nr", "radio_nr" or "vbi_nr" module options to select specific video/radio/vbi node numbers. This allows the
With these changes:
Thanks!
Hans
PATCH v2 2/3 media: open.rst: document devnode-centric and mc-centric types
In reply to Mauro Carvalho ChehabFrom: "[email protected]" <[email protected]>
When we added support for omap3, back in 2010, we added a new type of V4L2 devices that aren't fully controlled via the V4L2 device node. Yet, we never made it clear, at the V4L2 spec, about the differences between both types.
Let's document them with the current implementation.
--- Documentation/media/uapi/v4l/open.rst | 53 +++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)
Documentation/media/uapi/v4l/open.rst +53 -0
@@ -6,6 +6,59 @@ Opening and Closing Devices *************************** +Types of V4L2 hardware control +============================== + +V4L2 hardware is usually complex: support for the hardware is implemented +via a main driver (also known as bridge driver) and often several +additional drivers. The main driver always exposes one or +more **V4L2 device nodes** (see :ref:`v4l2_device_naming`). + +The other drivers are called **V4L2 sub-devices** and provide control to +other parts of the hardware usually connected via a serial bus (like +I²C, SMBus or SPI). Depending on the main driver, they can be implicitly +controlled directly by the main driver or explicitly via +the **V4L2 sub-device API** (see :ref:`subdev`). + +When V4L2 was originally designed, there was only one type of hardware +control. The entire V4L2 hardware is controlled via the +**V4L2 device nodes**. We refer to this kind of control as +**V4L2 device node centric** (or, simply, **vdev-centric**). + +Since the end of 2010, a new type of V4L2 hardware control was added, in +order to support complex devices that are common for embedded systems. +Those hardware are controlled mainly via the media controller and +sub-devices. So, they are called: **Media controller centric** +(or, simply, "**MC-centric**"). + +For **vdev-centric** hardware control, the hardware is controlled via +the **V4L2 device nodes**. They may optionally support the +:ref:`media controller API <media_controller>` as well, in order to let +the application to know with device nodes are available. + +.. note:: + + A **vdev-centric** may optionally expose V4L2 sub-devices via + :ref:`sub-device API <subdev>`. In that case, it has to implement + the :ref:`media controller API <media_controller>` as well. + +For **MC-centric** hardware control, before using the V4L2 hardware, +it is required to set the pipelines via the +:ref:`media controller API <media_controller>`. For those devices, the +sub-devices' configuration can be controlled via the +:ref:`sub-device API <subdev>`, whith creates one device node +per sub-device. + +In summary, for **MC-centric** hardware control: + +- The **V4L2 device** node is responsible for controlling the streaming + features; +- The **media controller device** is responsible to setup the pipelines; +- The **V4L2 sub-devices** are responsible for sub-device + specific settings. + + +.. _v4l2_device_naming: V4L2 Device Node Naming =======================
Signature · 1 line
2.13.3
Re: [PATCH v2 2/3] media: open.rst: document devnode-centric and mc-centric types
Quoted 32 lines · Mauro Carvalho Chehab
From: "[email protected]" <[email protected]>
When we added support for omap3, back in 2010, we added a new type of V4L2 devices that aren't fully controlled via the V4L2 device node. Yet, we never made it clear, at the V4L2 spec, about the differences between both types.
Let's document them with the current implementation.
Signed-off-by Mauro Carvalho Chehab <[email protected]>--- Documentation/media/uapi/v4l/open.rst | 53 +++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)Documentation/media/uapi/v4l/open.rst +10
-0@@ -6,6 +6,59 @@ Opening and Closing Devices *************************** +Types of V4L2 hardware control +============================== + +V4L2 hardware is usually complex: support for the hardware is implemented +via a main driver (also known as bridge driver) and often several +additional drivers. The main driver always exposes one or +more **V4L2 device nodes** (see :ref:`v4l2_device_naming`). + +The other drivers are called **V4L2 sub-devices** and provide control to +other parts of the hardware usually connected via a serial bus (like
Documentation/media/uapi/v4l/open.rst line 28
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +10
-0+I²C, SMBus or SPI). Depending on the main driver, they can be implicitly +controlled directly by the main driver or explicitly via +the **V4L2 sub-device API** (see :ref:`subdev`). + +When V4L2 was originally designed, there was only one type of hardware +control. The entire V4L2 hardware is controlled via the +**V4L2 device nodes**. We refer to this kind of control as +**V4L2 device node centric** (or, simply, **vdev-centric**). + +Since the end of 2010, a new type of V4L2 hardware control was added, in
Just drop 'the end of'.
s/, in/ in/
Documentation/media/uapi/v4l/open.rst line 30
Quoted 2 lines
Documentation/media/uapi/v4l/open.rst +2
-0+order to support complex devices that are common for embedded systems. +Those hardware are controlled mainly via the media controller and
Such hardware is
Documentation/media/uapi/v4l/open.rst line 37
Quoted 7 lines
Documentation/media/uapi/v4l/open.rst +7
-0+sub-devices. So, they are called: **Media controller centric** +(or, simply, "**MC-centric**"). + +For **vdev-centric** hardware control, the hardware is controlled via +the **V4L2 device nodes**. They may optionally support the +:ref:`media controller API <media_controller>` as well, in order to let +the application to know with device nodes are available.
to know with -> know which
Documentation/media/uapi/v4l/open.rst line 41
Quoted 4 lines
Documentation/media/uapi/v4l/open.rst +4
-0+ +.. note:: + + A **vdev-centric** may optionally expose V4L2 sub-devices via
I propose adding 'also' before 'expose' to indicate that it is in addition to the V4L2 device nodes that were mentioned in the previous paragraph.
Documentation/media/uapi/v4l/open.rst line 46
Quoted 5 lines
Documentation/media/uapi/v4l/open.rst +5
-0+ :ref:`sub-device API <subdev>`. In that case, it has to implement + the :ref:`media controller API <media_controller>` as well. + +For **MC-centric** hardware control, before using the V4L2 hardware, +it is required to set the pipelines via the
I'd reword this a bit:
For **MC-centric** hardware control it is required to configure the pipelines via the :ref:media controller API <media_controller> before the hardware can be used.
Documentation/media/uapi/v4l/open.rst line 47
Quoted 1 line
Documentation/media/uapi/v4l/open.rst +1
-0+:ref:`media controller API <media_controller>`. For those devices, the
s/those/such/
Documentation/media/uapi/v4l/open.rst line 49
Quoted 2 lines
Documentation/media/uapi/v4l/open.rst +2
-0+sub-devices' configuration can be controlled via the +:ref:`sub-device API <subdev>`, whith creates one device node
s/whith/which/
Quoted 6 lines
Documentation/media/uapi/v4l/open.rst +5
-0+per sub-device. + +In summary, for **MC-centric** hardware control: + +- The **V4L2 device** node is responsible for controlling the streaming
Documentation/media/uapi/v4l/open.rst line 64
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +7
-0+ features; +- The **media controller device** is responsible to setup the pipelines; +- The **V4L2 sub-devices** are responsible for sub-device + specific settings. + + +.. _v4l2_device_naming: V4L2 Device Node Naming =======================
The only thing I am not sure about is vdev-centric vs V4L2-centric. 'Laziness while typing' is not a convincing argument :-)
Regards,
Hans
Re: [PATCH v2 2/3] media: open.rst: document devnode-centric and mc-centric types
Em Fri, 25 Aug 2017 15:42:21 +0200
Hans Verkuil <[email protected]> escreveu:
Quoted 46 lines · Mauro Carvalho Chehab
Quoted 32 lines
From: "[email protected]" <[email protected]>
When we added support for omap3, back in 2010, we added a new type of V4L2 devices that aren't fully controlled via the V4L2 device node. Yet, we never made it clear, at the V4L2 spec, about the differences between both types.
Let's document them with the current implementation.
Signed-off-by Mauro Carvalho Chehab <[email protected]>--- Documentation/media/uapi/v4l/open.rst | 53 +++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)Documentation/media/uapi/v4l/open.rst +10
-0@@ -6,6 +6,59 @@ Opening and Closing Devices *************************** +Types of V4L2 hardware control +============================== + +V4L2 hardware is usually complex: support for the hardware is implemented +via a main driver (also known as bridge driver) and often several +additional drivers. The main driver always exposes one or +more **V4L2 device nodes** (see :ref:`v4l2_device_naming`). + +The other drivers are called **V4L2 sub-devices** and provide control to +other parts of the hardware usually connected via a serial bus (likeDocumentation/media/uapi/v4l/open.rst line 28
Quoted 10 lines
Documentation/media/uapi/v4l/open.rst +10
-0+I²C, SMBus or SPI). Depending on the main driver, they can be implicitly +controlled directly by the main driver or explicitly via +the **V4L2 sub-device API** (see :ref:`subdev`). + +When V4L2 was originally designed, there was only one type of hardware +control. The entire V4L2 hardware is controlled via the +**V4L2 device nodes**. We refer to this kind of control as +**V4L2 device node centric** (or, simply, **vdev-centric**). + +Since the end of 2010, a new type of V4L2 hardware control was added, inJust drop 'the end of'.
Quoted 1 line
s/, in/ in/
I anded by changing it to:
Later (kernel 2.6.39),
Quoted 58 lines
Documentation/media/uapi/v4l/open.rst line 30
Quoted 3 lines
Documentation/media/uapi/v4l/open.rst +2
-0+order to support complex devices that are common for embedded systems. +Those hardware are controlled mainly via the media controller andSuch hardware is
Documentation/media/uapi/v4l/open.rst line 37
Quoted 7 lines
Documentation/media/uapi/v4l/open.rst +7
-0+sub-devices. So, they are called: **Media controller centric** +(or, simply, "**MC-centric**"). + +For **vdev-centric** hardware control, the hardware is controlled via +the **V4L2 device nodes**. They may optionally support the +:ref:`media controller API <media_controller>` as well, in order to let +the application to know with device nodes are available.to know with -> know which
Documentation/media/uapi/v4l/open.rst line 41
Quoted 4 lines
Documentation/media/uapi/v4l/open.rst +4
-0+ +.. note:: + + A **vdev-centric** may optionally expose V4L2 sub-devices viaI propose adding 'also' before 'expose' to indicate that it is in addition to the V4L2 device nodes that were mentioned in the previous paragraph.
Documentation/media/uapi/v4l/open.rst line 46
Quoted 5 lines
Documentation/media/uapi/v4l/open.rst +5
-0+ :ref:`sub-device API <subdev>`. In that case, it has to implement + the :ref:`media controller API <media_controller>` as well. + +For **MC-centric** hardware control, before using the V4L2 hardware, +it is required to set the pipelines via theI'd reword this a bit:
For **MC-centric** hardware control it is required to configure the pipelines via the :ref:
media controller API <media_controller>before the hardware can be used.Documentation/media/uapi/v4l/open.rst line 47
Quoted 1 line
Documentation/media/uapi/v4l/open.rst +1
-0+:ref:`media controller API <media_controller>`. For those devices, thes/those/such/
Documentation/media/uapi/v4l/open.rst line 49
Quoted 2 lines
Documentation/media/uapi/v4l/open.rst +2
-0+sub-devices' configuration can be controlled via the +:ref:`sub-device API <subdev>`, whith creates one device nodes/whith/which/
Quoted 13 lines
Documentation/media/uapi/v4l/open.rst +12
-0+per sub-device. + +In summary, for **MC-centric** hardware control: + +- The **V4L2 device** node is responsible for controlling the streaming + features; +- The **media controller device** is responsible to setup the pipelines; +- The **V4L2 sub-devices** are responsible for sub-device + specific settings. + + +.. _v4l2_device_naming:
Quoted 2 lines
Documentation/media/uapi/v4l/open.rst line 64
Quoted 2 lines
Documentation/media/uapi/v4l/open.rst +0
-0V4L2 Device Node Naming =======================
Changes done. I'll place on a new version of this series.
Quoted 4 lines
Quoted 1 line
The only thing I am not sure about is vdev-centric vs V4L2-centric. 'Laziness while typing' is not a convincing argument :-)
Despite the laziness of playing a lot with shifts to type V4L2-centric, the thing that bothers me with V4L2 is that the subdev API is part of V4L2 spec. So, IMHO, it is still a confusing name.
As this actually refers to "V4L2 Device Node", with is now properly specified (due to patch 1/3), "vdev" is a good shortcut for it.
Let's reverse the question: what's wrong with "vdev-centric"?
Thanks,
Mauro
PATCH v2 3/3 media: videodev2: add a flag for MC-centric devices
In reply to Mauro Carvalho ChehabFrom: Mauro Carvalho Chehab <[email protected]>
As both vdev-centric and MC-centric devices may implement the same APIs, we need a flag to allow userspace to distinguish between them.
--- Documentation/media/uapi/v4l/open.rst | 11 +++++++++++ Documentation/media/uapi/v4l/vidioc-querycap.rst | 5 +++++ include/uapi/linux/videodev2.h | 2 ++ 3 files changed, 18 insertions(+)
Documentation/media/uapi/v4l/open.rst +11 -0
@@ -6,6 +6,10 @@ Opening and Closing Devices *************************** + +.. _v4l2_hardware_control: + + Types of V4L2 hardware control ==============================
@@ -49,6 +53,13 @@ sub-devices' configuration can be controlled via the :ref:`sub-device API <subdev>`, whith creates one device node per sub-device. +.. attention:: + + Devices that require **mc-centric** hardware control should report + a ``V4L2_MC_CENTRIC`` :c:type:`v4l2_capability` flag + (see :ref:`VIDIOC_QUERYCAP`). + + In summary, for **MC-centric** hardware control: - The **V4L2 device** node is responsible for controlling the streaming
Documentation/media/uapi/v4l/vidioc-querycap.rst +5 -0
@@ -252,6 +252,11 @@ specification the ioctl returns an ``EINVAL`` error code. * - ``V4L2_CAP_TOUCH`` - 0x10000000 - This is a touch device. + * - ``V4L2_MC_CENTRIC`` + - 0x20000000 + - Indicates that the device require **mc-centric** hardware + control, and thus can't be used by **v4l2-centric** applications. + See :ref:`v4l2_hardware_control` for more details. * - ``V4L2_CAP_DEVICE_CAPS`` - 0x80000000 - The driver fills the ``device_caps`` field. This capability can
include/uapi/linux/videodev2.h +2 -0
@@ -460,6 +460,8 @@ struct v4l2_capability {#define V4L2_CAP_TOUCH 0x10000000/* Is a touch device */ +#define V4L2_CAP_MC_CENTRIC 0x20000000/* Device require mc-centric hardware control */ +#define V4L2_CAP_DEVICE_CAPS 0x80000000/* sets device capabilities field */ /*
Signature · 1 line
2.13.3