Linux/AM5718: User pointer support for V4L2 capture

150436

Part Number: AM5718

Tool/software: Linux

Hi,

We are trying to use USER pointer instead of mmap, but when we request for user pointer using VIDIOC_REQBUFS ioctl, it is returning error. How to enable this in v4l2 driver?

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

The software team have been notified. They will respond here.

0 Manisha Agrawal over 8 years ago in reply to Biser Gatchev-XID

TI__Mastermind 22946 points

Please share more details. Who is allocating the buffer, how are you trying to get the user pointer? Please create the problem in standalone test bench that can be replicated on Processor SDK 4.1.

0 150436 over 8 years ago in reply to Manisha Agrawal

Prodigy 160 points

Hi Manisha,

Please find the v4l2 capture application in the below link. It works for mmap, but fails in case of user pointer.
www.linuxtv.org/.../capture-example.html

In init_userp function we are allocating memory.
when we run the application we getting /dev/video0 does not support user pointer i/o.

0 Manisha Agrawal over 8 years ago in reply to 150436

TI__Mastermind 22946 points

Is this using Processor SDK on AM57x GP/IDK EVM?? If yes, which version of Processor SDK are you using?? Are you trying to use VIP capture or VPE driver memory to memory operations? Both are V4l2 device. Please use below instruction to find which device you want to use. For example, using Processor SDK 4.1 on AM57x GP EVM, below v4l2 devices are listed.

# v4l2-ctl --list-devices

wbcap (platform:omapwb-cap):

/dev/video11

omapwb-m2m (platform:omapwb-m2m):

/dev/video10

vip (platform:vip):

/dev/video1

vpe (platform:vpe):

/dev/video0

If you want to configure vpe device, please follow the v4l2-m2m example here -

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Linux/AM5718: User pointer support for V4L2 capture