Re: [PATCH RFC 2/2] staging: vc04_services: Document VCHIQ character device

Stefan Wahren
2025-05-21T11:39:25Z

Hi,

Am 21.05.25 um 13:28 schrieb Laurent Pinchart:
> On Wed, May 21, 2025 at 01:20:54PM +0200, Greg KH wrote:
>> On Sat, May 10, 2025 at 12:11:52AM +0200, Stefan Wahren wrote:
>>> From: Phil Elwell <phil@raspberrypi.com>
>>>
>>> Document the IOCTLs for the VCHIQ character device, which provide
>>> a userspace interface to access the VideoCore VPU of the
>>> Raspberry Pi. Several ARM side libraries make use of it like EGL,
>>> MMAL and OpenMAX.
>>>
>>> Link: https://github.com/raspberrypi/linux/pull/6801
>>> Signed-off-by: Phil Elwell <phil@raspberrypi.com>
>>> [wahrenst@gmx.net: Rewrite commit log]
>>> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
>>> ---
>>> .../vc04_services/Documentation/vchiq-cdev | 87 +++++++++++++++++++
>>> 1 file changed, 87 insertions(+)
>>> create mode 100644 drivers/staging/vc04_services/Documentation/vchiq-cdev
>>>
>>> diff --git a/drivers/staging/vc04_services/Documentation/vchiq-cdev b/drivers/staging/vc04_services/Documentation/vchiq-cdev
>>> new file mode 100644
>>> index 000000000000..99ab2567643e
>>> --- /dev/null
>>> +++ b/drivers/staging/vc04_services/Documentation/vchiq-cdev
>>> @@ -0,0 +1,87 @@
>>> +What: /dev/vchiq
>>> +Date: October 2016
>>> +KernelVersion: 4.9
>>> +Contact: kernel-list@raspberrypi.com
>>> +Description:
>>> + The ioctl interface for the VCHIQ character device.
>>> + Following actions are supported:
>>> +
>>> + * VCHIQ_IOC_CONNECT:
>>> + Establish/confirm the link to the VPU peer.
>> I understand the need, but this does not document the parameters to the
>> ioctls, so it's not all that useful. How about just a normal
>> documentation file with this all written out?
> That would be my preference too, somewhere in
> Documentation/userspace-api/.
>
could you please point me to a comparable IOCTL documenation to better
understand your expectations?