Add the helper API v4l2_async_pad_init_and_register_subdev(), which
combines media_entity_pads_init(), v4l2_subdev_init_finalize(), and
v4l2_async_register_subdev() into a single call.

Reduce code duplication and simplify error handling in drivers.

Only change dwc and cdns. If agree add API, more driver can be simplified.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Frank Li (3):
      media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()
      media: synopsys: Use v4l2_async_pad_init_and_register_subdev() to simplify code
      media: cadence: cdns-csi2rx: Use v4l2_async_pad_init_and_register_subdev() to simplify code

 drivers/media/platform/cadence/cdns-csi2rx.c     | 18 ++++----------
 drivers/media/platform/synopsys/dw-mipi-csi2rx.c | 15 +++---------
 drivers/media/v4l2-core/v4l2-async.c             | 30 ++++++++++++++++++++++++
 include/media/v4l2-async.h                       | 18 ++++++++++++++
 4 files changed, 55 insertions(+), 26 deletions(-)
---
base-commit: bc0bfce7d0f8204e0bbadcee72e87ad9ec105c73
change-id: 20260210-v4l2_init_register-0e6d0adcfa21

Best regards,
--
Frank Li <Frank.Li@nxp.com>

Hi Frank,

Thanks for your patches.

On 2/10/26 22:42, Frank Li wrote:
> Add the helper API v4l2_async_pad_init_and_register_subdev(), which
> combines media_entity_pads_init(), v4l2_subdev_init_finalize(), and
> v4l2_async_register_subdev() into a single call.

I think this is a good idea, but can you extend that to offer variants
for v4l2_async_register_subdev_sensor and v4l2_device_register_subdev too?

The function names are awfully long, though. Can we call this
    media_register_subdev{_async,_sensor,}
maybe?

Best regards,
Michael

> 
> Reduce code duplication and simplify error handling in drivers.
> 
> Only change dwc and cdns. If agree add API, more driver can be simplified.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> Frank Li (3):
>       media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()
>       media: synopsys: Use v4l2_async_pad_init_and_register_subdev() to simplify code
>       media: cadence: cdns-csi2rx: Use v4l2_async_pad_init_and_register_subdev() to simplify code
> 
>  drivers/media/platform/cadence/cdns-csi2rx.c     | 18 ++++----------
>  drivers/media/platform/synopsys/dw-mipi-csi2rx.c | 15 +++---------
>  drivers/media/v4l2-core/v4l2-async.c             | 30 ++++++++++++++++++++++++
>  include/media/v4l2-async.h                       | 18 ++++++++++++++
>  4 files changed, 55 insertions(+), 26 deletions(-)
> ---
> base-commit: bc0bfce7d0f8204e0bbadcee72e87ad9ec105c73
> change-id: 20260210-v4l2_init_register-0e6d0adcfa21
> 
> Best regards,
> --
> Frank Li <Frank.Li@nxp.com>
>

On Fri, Feb 20, 2026 at 10:01:01AM +0100, Michael Riesch wrote:
> Hi Frank,
>
> Thanks for your patches.
>
> On 2/10/26 22:42, Frank Li wrote:
> > Add the helper API v4l2_async_pad_init_and_register_subdev(), which
> > combines media_entity_pads_init(), v4l2_subdev_init_finalize(), and
> > v4l2_async_register_subdev() into a single call.
>
> I think this is a good idea, but can you extend that to offer variants
> for v4l2_async_register_subdev_sensor and v4l2_device_register_subdev too?
>
> The function names are awfully long, though. Can we call this
>     media_register_subdev{_async,_sensor,}
> maybe?

How about media_async_register_subdev()? which basic align other API
naming. I want to add more helper APIs.

drivers/media/platform/synopsys/dw-mipi-csi2rx.c have about 600 lines code
but related hardware register codes are below 20 line, only few registers.

I just post this simple version to gather feedback from maintainers and
reviewers on the overall approach.

Frank

>
> Best regards,
> Michael
>
> >
> > Reduce code duplication and simplify error handling in drivers.
> >
> > Only change dwc and cdns. If agree add API, more driver can be simplified.
> >
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> > Frank Li (3):
> >       media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()
> >       media: synopsys: Use v4l2_async_pad_init_and_register_subdev() to simplify code
> >       media: cadence: cdns-csi2rx: Use v4l2_async_pad_init_and_register_subdev() to simplify code
> >
> >  drivers/media/platform/cadence/cdns-csi2rx.c     | 18 ++++----------
> >  drivers/media/platform/synopsys/dw-mipi-csi2rx.c | 15 +++---------
> >  drivers/media/v4l2-core/v4l2-async.c             | 30 ++++++++++++++++++++++++
> >  include/media/v4l2-async.h                       | 18 ++++++++++++++
> >  4 files changed, 55 insertions(+), 26 deletions(-)
> > ---
> > base-commit: bc0bfce7d0f8204e0bbadcee72e87ad9ec105c73
> > change-id: 20260210-v4l2_init_register-0e6d0adcfa21
> >
> > Best regards,
> > --
> > Frank Li <Frank.Li@nxp.com>
> >
>

Hi Frank,

On 2/20/26 16:46, Frank Li wrote:
> On Fri, Feb 20, 2026 at 10:01:01AM +0100, Michael Riesch wrote:
>> Hi Frank,
>>
>> Thanks for your patches.
>>
>> On 2/10/26 22:42, Frank Li wrote:
>>> Add the helper API v4l2_async_pad_init_and_register_subdev(), which
>>> combines media_entity_pads_init(), v4l2_subdev_init_finalize(), and
>>> v4l2_async_register_subdev() into a single call.
>>
>> I think this is a good idea, but can you extend that to offer variants
>> for v4l2_async_register_subdev_sensor and v4l2_device_register_subdev too?
>>
>> The function names are awfully long, though. Can we call this
>>     media_register_subdev{_async,_sensor,}
>> maybe?
> 
> How about media_async_register_subdev()? which basic align other API
> naming. I want to add more helper APIs.

This would work for me.

> drivers/media/platform/synopsys/dw-mipi-csi2rx.c have about 600 lines code
> but related hardware register codes are below 20 line, only few registers.
> 
> I just post this simple version to gather feedback from maintainers and
> reviewers on the overall approach.

Sure, that's reasonable.

Just saying that if you plan to provide more helpers, there may be a
smart way to do so without copying the new helper function code three
times. Maybe

int helper(struct v4l2_subdev* sd, u16 num_pads, struct media_pad *pads,
	   struct module *module,
	   int (*cb)(struct v4l2_subdev *, struct module *))

and

#define media_async_register_subdev(sd, num_pads, pads) \
	helper(sd, num_pads, pads, THIS_MODULE,
	__v4l2_async_register_subdev)

or so?

Best regards,
Michael

> 
> Frank
> 
>>
>> Best regards,
>> Michael
>>
>>>
>>> Reduce code duplication and simplify error handling in drivers.
>>>
>>> Only change dwc and cdns. If agree add API, more driver can be simplified.
>>>
>>> Signed-off-by: Frank Li <Frank.Li@nxp.com>
>>> ---
>>> Frank Li (3):
>>>       media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()
>>>       media: synopsys: Use v4l2_async_pad_init_and_register_subdev() to simplify code
>>>       media: cadence: cdns-csi2rx: Use v4l2_async_pad_init_and_register_subdev() to simplify code
>>>
>>>  drivers/media/platform/cadence/cdns-csi2rx.c     | 18 ++++----------
>>>  drivers/media/platform/synopsys/dw-mipi-csi2rx.c | 15 +++---------
>>>  drivers/media/v4l2-core/v4l2-async.c             | 30 ++++++++++++++++++++++++
>>>  include/media/v4l2-async.h                       | 18 ++++++++++++++
>>>  4 files changed, 55 insertions(+), 26 deletions(-)
>>> ---
>>> base-commit: bc0bfce7d0f8204e0bbadcee72e87ad9ec105c73
>>> change-id: 20260210-v4l2_init_register-0e6d0adcfa21
>>>
>>> Best regards,
>>> --
>>> Frank Li <Frank.Li@nxp.com>
>>>
>>