[PATCH 0/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[PATCH 0/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[Frank Li]

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>

[PATCH 1/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[Frank Li]

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.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/media/v4l2-core/v4l2-async.c | 30 ++++++++++++++++++++++++++++++
 include/media/v4l2-async.h           | 18 ++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index 1c08bba9ecb91f46b7479da613d6c1688d4b0b5c..65e4aa46372a02f9ddc04571436f46c90259e200 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -19,6 +19,7 @@
 #include <linux/slab.h>
 #include <linux/types.h>
 
+#include <media/media-entity.h>
 #include <media/v4l2-async.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-fwnode.h>
@@ -881,6 +882,35 @@ int __v4l2_async_register_subdev(struct v4l2_subdev *sd, struct module *module)
 }
 EXPORT_SYMBOL(__v4l2_async_register_subdev);
 
+int __v4l2_async_pad_init_and_register_subdev(struct v4l2_subdev *sd,
+					      u16 num_pads,
+					      struct media_pad *pads,
+					      struct module *module)
+{
+	int ret;
+
+	ret = media_entity_pads_init(&sd->entity, num_pads, pads);
+	if (ret)
+		return ret;
+
+	ret = v4l2_subdev_init_finalize(sd);
+	if (ret)
+		goto err_entity_cleanup;
+
+	ret = __v4l2_async_register_subdev(sd, module);
+	if (ret)
+		goto err_subdev_cleanup;
+
+	return 0;
+
+err_subdev_cleanup:
+	v4l2_subdev_cleanup(sd);
+err_entity_cleanup:
+	media_entity_cleanup(&sd->entity);
+	return ret;
+}
+EXPORT_SYMBOL(__v4l2_async_pad_init_and_register_subdev);
+
 void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
 {
 	struct v4l2_async_connection *asc, *asc_tmp;
diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
index f26c323e9c963065fd7c19d6d9835df1194bc069..81f1f418a246902178d5fa8f9d5e48b14301386f 100644
--- a/include/media/v4l2-async.h
+++ b/include/media/v4l2-async.h
@@ -336,6 +336,24 @@ int __v4l2_async_register_subdev(struct v4l2_subdev *sd, struct module *module);
 int __must_check
 v4l2_async_register_subdev_sensor(struct v4l2_subdev *sd);
 
+struct media_pad;
+int __must_check
+__v4l2_async_pad_init_and_register_subdev(struct v4l2_subdev *sd, u16 num_pads,
+					  struct media_pad *pads,
+					  struct module *module);
+/**
+ * v4l2_async_pad_init_and_register_subdev - Initialize the entity pads and
+ *					     registers a sub-device to the
+ *					     asynchronous subdevice framework
+ * @sd: pointer to &struct v4l2_subdev
+ * @num_pads: total number of sink and source pads
+ * @pads: Array of @num_pads pads.
+ *
+ * Returns an error on failure, 0 on success.
+ */
+#define v4l2_async_pad_init_and_register_subdev(sd, num_pads, pads)	\
+	__v4l2_async_pad_init_and_register_subdev(sd, num_pads, pads,	\
+						  THIS_MODULE)
 /**
  * v4l2_async_unregister_subdev - unregisters a sub-device to the asynchronous
  *	subdevice framework

-- 
2.43.0

[PATCH 2/3] media: synopsys: Use v4l2_async_pad_init_and_register_subdev() to simplify code

[Frank Li]

Use v4l2_async_pad_init_and_register_subdev() to simplify the code.

No functional changes.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/media/platform/synopsys/dw-mipi-csi2rx.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/media/platform/synopsys/dw-mipi-csi2rx.c b/drivers/media/platform/synopsys/dw-mipi-csi2rx.c
index 5dc55b59d6aeed4b6cb207c8e2ebe0fb3c462644..64ad7ac62c085400e2544cceb91cfa55c66910bd 100644
--- a/drivers/media/platform/synopsys/dw-mipi-csi2rx.c
+++ b/drivers/media/platform/synopsys/dw-mipi-csi2rx.c
@@ -681,15 +681,10 @@ static int dw_mipi_csi2rx_register(struct dw_mipi_csi2rx_device *csi2)
 	pads[DW_MIPI_CSI2RX_PAD_SINK].flags = MEDIA_PAD_FL_SINK |
 					      MEDIA_PAD_FL_MUST_CONNECT;
 	pads[DW_MIPI_CSI2RX_PAD_SRC].flags = MEDIA_PAD_FL_SOURCE;
-	ret = media_entity_pads_init(&sd->entity, DW_MIPI_CSI2RX_PAD_MAX, pads);
-	if (ret)
-		goto err_notifier_unregister;
-
-	ret = v4l2_subdev_init_finalize(sd);
-	if (ret)
-		goto err_entity_cleanup;
 
-	ret = v4l2_async_register_subdev(sd);
+	ret = v4l2_async_pad_init_and_register_subdev(sd,
+						      DW_MIPI_CSI2RX_PAD_MAX,
+						      pads);
 	if (ret) {
 		dev_err(sd->dev, "failed to register CSI-2 subdev\n");
 		goto err_subdev_cleanup;
@@ -698,10 +693,6 @@ static int dw_mipi_csi2rx_register(struct dw_mipi_csi2rx_device *csi2)
 	return 0;
 
 err_subdev_cleanup:
-	v4l2_subdev_cleanup(sd);
-err_entity_cleanup:
-	media_entity_cleanup(&sd->entity);
-err_notifier_unregister:
 	v4l2_async_nf_unregister(&csi2->notifier);
 	v4l2_async_nf_cleanup(&csi2->notifier);
 err:

-- 
2.43.0

[PATCH 3/3] media: cadence: cdns-csi2rx: Use v4l2_async_pad_init_and_register_subdev() to simplify code

[Frank Li]

Use v4l2_async_pad_init_and_register_subdev() to simplify the code.

No functional changes.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
build test only
---
 drivers/media/platform/cadence/cdns-csi2rx.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
index 8c19f125da3e50f55a0ae280b05e7918ce115101..1a18a9d0ea602c91c07a4bf4573ec0346edc7650 100644
--- a/drivers/media/platform/cadence/cdns-csi2rx.c
+++ b/drivers/media/platform/cadence/cdns-csi2rx.c
@@ -855,11 +855,6 @@ static int csi2rx_probe(struct platform_device *pdev)
 	csi2rx->subdev.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
 	csi2rx->subdev.entity.ops = &csi2rx_media_ops;
 
-	ret = media_entity_pads_init(&csi2rx->subdev.entity, CSI2RX_PAD_MAX,
-				     csi2rx->pads);
-	if (ret)
-		goto err_cleanup;
-
 	csi2rx->error_irq = platform_get_irq_byname_optional(pdev, "error_irq");
 
 	if (csi2rx->error_irq < 0) {
@@ -875,13 +870,11 @@ static int csi2rx_probe(struct platform_device *pdev)
 		}
 	}
 
-	ret = v4l2_subdev_init_finalize(&csi2rx->subdev);
-	if (ret)
-		goto err_cleanup;
-
-	ret = v4l2_async_register_subdev(&csi2rx->subdev);
+	ret = v4l2_async_pad_init_and_register_subdev(&csi2rx->subdev,
+						      CSI2RX_PAD_MAX,
+						      csi2rx->pads);
 	if (ret < 0)
-		goto err_free_state;
+		goto err_cleanup;
 
 	dev_info(&pdev->dev,
 		 "Probed CSI2RX with %u/%u lanes, %u streams, %s D-PHY\n",
@@ -891,12 +884,9 @@ static int csi2rx_probe(struct platform_device *pdev)
 
 	return 0;
 
-err_free_state:
-	v4l2_subdev_cleanup(&csi2rx->subdev);
 err_cleanup:
 	v4l2_async_nf_unregister(&csi2rx->notifier);
 	v4l2_async_nf_cleanup(&csi2rx->notifier);
-	media_entity_cleanup(&csi2rx->subdev.entity);
 err_free_priv:
 	kfree(csi2rx);
 	return ret;

-- 
2.43.0

Re: [PATCH 0/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[Michael Riesch]

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>
> 

Re: [PATCH 0/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[Frank Li]

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>
> >
>

Re: [PATCH 0/3] media: v4l: async: add helper API v4l2_async_pad_init_and_register_subdev()

[Michael Riesch]

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>
>>>
>>