[PATCH v4 0/4] media: imx-mipi-csis: Get the number of active lanes from mbus_config

[PATCH v4 0/4] media: imx-mipi-csis: Get the number of active lanes from mbus_config

[Isaac Scott]

It is possible that the number of desired active MIPI CSI2 data lanes
does not match the maximum listed in device tree. Add a helper function
to v4l2_common that calls the get_mbus_config op to get the number of
actively used data lanes in drivers that support it.

Compare it to the number of lanes configured in device tree, and if its
invalid, use the number present in device tree.

This series also uses the helper in imx-mipi-csis driver to set the
currently configured num_data_lanes, while keeping track of the number
of data lanes set in device tree to ensure we can still use all possible
lanes if we need to, and the upstream subdev driver requests them.

Tested on v6.15, compile tested on media/next.

---------

Changes v3 -> v4:

- Updated base tree to media/next
- Used local 'lanes' variable consistently in
  v4l2_get_active_data_lanes()
- Removed device tree references in documentation
- Made comment a single line
- Collected tag for patch 1/4
- Removed unnecessary num_data_lanes assignments in async_register in
  imx-mipi-csis
- Removed some debug print changes
- Checked return value of v4l2_get_active_data_lanes() before assignment
  to csis->num_data_lanes
- Added patch to move redundant debug print in mipi_csis_probe()

Changes v2 -> v3:

- Rename dt_lanes to max_data_lanes
- Remove check for < 0 on unsigned int max_data_lanes in
  v4l2_get_active_data_lanes()
- Added comment to explain that mbus_config is expected to be zeroed at
  init in drivers implementing get_mbus_config subdev pad op
- Wrapped signature in header file and source for
  v4l2_get_active_data_lanes()
- Added kernel-doc documentation for v4l2_get_active_data_lanes()
- Added debug message to indicate an invalid number of active lanes
- Changed csis->max_data_lanes to csis->num_data_lanes
- Changed uses of csis->bus.num_data_lanes to csis->num_data_lanes where
  appropriate to make csis->bus immutable after probe

Changes v1 -> v2:

- Added helper function to get active data lanes in v4l2-common
- Store the maximum data lanes possible, as configured in device tree
- Added media: prefix to commit titles

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
Isaac Scott (4):
      media: v4l: Add helper to get number of active lanes via a pad
      media: imx-mipi-csis: Move redundant debug print in probe
      media: imx-mipi-csis: Store the number of data_lanes configured in dt
      media: imx-mipi-csis: Get number of active lanes via mbus_config

 drivers/media/platform/nxp/imx-mipi-csis.c | 19 ++++++++++++-------
 drivers/media/v4l2-core/v4l2-common.c      | 29 +++++++++++++++++++++++++++++
 include/media/v4l2-common.h                | 20 ++++++++++++++++++++
 3 files changed, 61 insertions(+), 7 deletions(-)
---
base-commit: 40b7a19f321e65789612ebaca966472055dab48c
change-id: 20250925-active-data-lanes-b5d994ff024a

Best regards,
-- 
Isaac Scott <isaac.scott@ideasonboard.com>

[PATCH v4 1/4] media: v4l: Add helper to get number of active lanes via a pad

[Isaac Scott]

Sometimes, users will not use all of the MIPI CSI 2 lanes available when
connecting to the MIPI CSI receiver of their device. Add a helper
function that checks the mbus_config for the device driver to allow
users to define the number of active data lanes through the
get_mbus_config op.

If the driver does not implement this op, fall back to using the maximum
number of lanes available.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-common.c | 29 +++++++++++++++++++++++++++++
 include/media/v4l2-common.h           | 20 ++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index b367d479d6b3..2b4cec25e751 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -573,6 +573,35 @@ s64 v4l2_get_link_freq(const struct media_pad *pad, unsigned int mul,
 	return v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div);
 }
 EXPORT_SYMBOL_GPL(v4l2_get_link_freq);
+
+unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad,
+					unsigned int max_data_lanes)
+{
+	struct v4l2_mbus_config mbus_config = {};
+	struct v4l2_subdev *sd;
+	unsigned int lanes;
+	int ret;
+
+	sd = media_entity_to_v4l2_subdev(pad->entity);
+	ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index,
+			       &mbus_config);
+	if (ret < 0 && ret != -ENOIOCTLCMD)
+		return ret;
+
+	/* This relies on the mbus_config being zeroed at init time */
+	lanes = mbus_config.bus.mipi_csi2.num_data_lanes;
+	if (!lanes)
+		return max_data_lanes;
+
+	if (lanes > max_data_lanes) {
+		dev_dbg(sd->dev, "Active data lanes (%u) exceeds max (%u)\n",
+			lanes, max_data_lanes);
+		return -EINVAL;
+	}
+
+	return lanes;
+}
+EXPORT_SYMBOL_GPL(v4l2_get_active_data_lanes);
 #endif
 
 /*
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 5c0a7f6b5bb6..950df46cb27a 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -581,6 +581,26 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
 #ifdef CONFIG_MEDIA_CONTROLLER
 s64 v4l2_get_link_freq(const struct media_pad *pad, unsigned int mul,
 		       unsigned int div);
+
+/**
+ * v4l2_get_active_data_lanes - Get number of active data lanes from driver
+ *
+ * @pad: The transmitter's media pad.
+ * @max_data_lanes: The maximum number of active data lanes supported by
+ *		    the MIPI CSI link in hardware.
+ *
+ * This function is intended for obtaining the number of data lanes that are
+ * actively being used by the driver for a MIPI CSI-2 device on a given media pad.
+ * This information is derived from a mbus_config fetched from a device driver
+ * using the get_mbus_config v4l2_subdev pad op.
+ *
+ * Return:
+ * * >0: Number of active data lanes
+ * * %-EINVAL: Number of active data lanes is invalid, as it exceeds the maximum
+ *	       supported data lanes.
+ */
+unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad,
+					unsigned int max_data_lanes);
 #endif
 
 void v4l2_simplify_fraction(u32 *numerator, u32 *denominator,

-- 
2.43.0

[PATCH v4 2/4] media: imx-mipi-csis: Move redundant debug print in probe

[Isaac Scott]

The number of data lanes is already printed as part of
mipi_csis_async_register(), making the first part of this print
redundant. Remove the redundant print, and move the debug print for
clock frequency to mipi_csis_parse_dt().

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/platform/nxp/imx-mipi-csis.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
index d5de7854f579..7c2a679dca2e 100644
--- a/drivers/media/platform/nxp/imx-mipi-csis.c
+++ b/drivers/media/platform/nxp/imx-mipi-csis.c
@@ -1481,6 +1481,7 @@ static int mipi_csis_parse_dt(struct mipi_csis_device *csis)
 	struct device_node *node = csis->dev->of_node;
 
 	of_property_read_u32(node, "clock-frequency", &csis->clk_frequency);
+	dev_dbg(csis->dev, "clock frequency: %u\n", csis->clk_frequency);
 
 	csis->num_channels = 1;
 	of_property_read_u32(node, "fsl,num-channels", &csis->num_channels);
@@ -1566,9 +1567,6 @@ static int mipi_csis_probe(struct platform_device *pdev)
 			goto err_unregister_all;
 	}
 
-	dev_info(dev, "lanes: %d, freq: %u\n",
-		 csis->bus.num_data_lanes, csis->clk_frequency);
-
 	return 0;
 
 err_unregister_all:

-- 
2.43.0

Re: [PATCH v4 2/4] media: imx-mipi-csis: Move redundant debug print in probe

[Frank Li]

On Thu, Sep 25, 2025 at 04:54:27PM +0100, Isaac Scott wrote:
> The number of data lanes is already printed as part of
> mipi_csis_async_register(), making the first part of this print
> redundant. Remove the redundant print, and move the debug print for
> clock frequency to mipi_csis_parse_dt().
>
> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index d5de7854f579..7c2a679dca2e 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -1481,6 +1481,7 @@ static int mipi_csis_parse_dt(struct mipi_csis_device *csis)
>  	struct device_node *node = csis->dev->of_node;
>
>  	of_property_read_u32(node, "clock-frequency", &csis->clk_frequency);
> +	dev_dbg(csis->dev, "clock frequency: %u\n", csis->clk_frequency);
>
>  	csis->num_channels = 1;
>  	of_property_read_u32(node, "fsl,num-channels", &csis->num_channels);
> @@ -1566,9 +1567,6 @@ static int mipi_csis_probe(struct platform_device *pdev)
>  			goto err_unregister_all;
>  	}
>
> -	dev_info(dev, "lanes: %d, freq: %u\n",
> -		 csis->bus.num_data_lanes, csis->clk_frequency);
> -
>  	return 0;
>
>  err_unregister_all:
>
> --
> 2.43.0
>

[PATCH v4 3/4] media: imx-mipi-csis: Store the number of data_lanes configured in dt

[Isaac Scott]

The number of active data lanes in use on a MIPI CSI2 bus is not
necessarily always the maximum. To allow us to configure the number of
data lanes actively in use, store the maximum to ensure we can configure
a number of data lanes that is supported.

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/platform/nxp/imx-mipi-csis.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
index 7c2a679dca2e..838a1ad123b5 100644
--- a/drivers/media/platform/nxp/imx-mipi-csis.c
+++ b/drivers/media/platform/nxp/imx-mipi-csis.c
@@ -351,6 +351,8 @@ struct mipi_csis_device {
 	u32 hs_settle;
 	u32 clk_settle;
 
+	unsigned int num_data_lanes;
+
 	spinlock_t slock;	/* Protect events */
 	struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
 	struct dentry *debugfs_root;
@@ -573,7 +575,7 @@ static void mipi_csis_system_enable(struct mipi_csis_device *csis, int on)
 	val = mipi_csis_read(csis, MIPI_CSIS_DPHY_CMN_CTRL);
 	val &= ~MIPI_CSIS_DPHY_CMN_CTRL_ENABLE;
 	if (on) {
-		mask = (1 << (csis->bus.num_data_lanes + 1)) - 1;
+		mask = (1 << (csis->num_data_lanes + 1)) - 1;
 		val |= (mask & MIPI_CSIS_DPHY_CMN_CTRL_ENABLE);
 	}
 	mipi_csis_write(csis, MIPI_CSIS_DPHY_CMN_CTRL, val);
@@ -623,7 +625,7 @@ static int mipi_csis_calculate_params(struct mipi_csis_device *csis,
 
 	/* Calculate the line rate from the pixel rate. */
 	link_freq = v4l2_get_link_freq(csis->source.pad, csis_fmt->width,
-				       csis->bus.num_data_lanes * 2);
+				       csis->num_data_lanes * 2);
 	if (link_freq < 0) {
 		dev_err(csis->dev, "Unable to obtain link frequency: %d\n",
 			(int)link_freq);
@@ -668,7 +670,7 @@ static void mipi_csis_set_params(struct mipi_csis_device *csis,
 				 const struct v4l2_mbus_framefmt *format,
 				 const struct csis_pix_format *csis_fmt)
 {
-	int lanes = csis->bus.num_data_lanes;
+	int lanes = csis->num_data_lanes;
 	u32 val;
 
 	val = mipi_csis_read(csis, MIPI_CSIS_CMN_CTRL);
@@ -1366,8 +1368,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
 	}
 
 	csis->bus = vep.bus.mipi_csi2;
+	csis->num_data_lanes = csis->bus.num_data_lanes;
 
-	dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
+	dev_dbg(csis->dev, "max data lanes: %d\n", csis->bus.num_data_lanes);
 	dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
 
 	asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,

-- 
2.43.0

Re: [PATCH v4 3/4] media: imx-mipi-csis: Store the number of data_lanes configured in dt

[Frank Li]

On Thu, Sep 25, 2025 at 04:54:28PM +0100, Isaac Scott wrote:
> The number of active data lanes in use on a MIPI CSI2 bus is not
> necessarily always the maximum. To allow us to configure the number of
> data lanes actively in use, store the maximum to ensure we can configure
> a number of data lanes that is supported.
>

This patch just add num_data_lanes, and use csis->num_data_lanes instead
of bus.num_data_lanes.

So commit message not reflect what you did

"
media: imx-mipi-csis: Add num_data_lanes in mipi_csis_device

Add num_data_lanes field in mipi_csis_device, set equal to
csis->bus.num_data_lanes. Prepare to support cases where the number of
active data lanes differs from the maximum supported lanes.

No functional changes.
"

Frank

> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index 7c2a679dca2e..838a1ad123b5 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -351,6 +351,8 @@ struct mipi_csis_device {
>  	u32 hs_settle;
>  	u32 clk_settle;
>
> +	unsigned int num_data_lanes;
> +
>  	spinlock_t slock;	/* Protect events */
>  	struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
>  	struct dentry *debugfs_root;
> @@ -573,7 +575,7 @@ static void mipi_csis_system_enable(struct mipi_csis_device *csis, int on)
>  	val = mipi_csis_read(csis, MIPI_CSIS_DPHY_CMN_CTRL);
>  	val &= ~MIPI_CSIS_DPHY_CMN_CTRL_ENABLE;
>  	if (on) {
> -		mask = (1 << (csis->bus.num_data_lanes + 1)) - 1;
> +		mask = (1 << (csis->num_data_lanes + 1)) - 1;
>  		val |= (mask & MIPI_CSIS_DPHY_CMN_CTRL_ENABLE);
>  	}
>  	mipi_csis_write(csis, MIPI_CSIS_DPHY_CMN_CTRL, val);
> @@ -623,7 +625,7 @@ static int mipi_csis_calculate_params(struct mipi_csis_device *csis,
>
>  	/* Calculate the line rate from the pixel rate. */
>  	link_freq = v4l2_get_link_freq(csis->source.pad, csis_fmt->width,
> -				       csis->bus.num_data_lanes * 2);
> +				       csis->num_data_lanes * 2);
>  	if (link_freq < 0) {
>  		dev_err(csis->dev, "Unable to obtain link frequency: %d\n",
>  			(int)link_freq);
> @@ -668,7 +670,7 @@ static void mipi_csis_set_params(struct mipi_csis_device *csis,
>  				 const struct v4l2_mbus_framefmt *format,
>  				 const struct csis_pix_format *csis_fmt)
>  {
> -	int lanes = csis->bus.num_data_lanes;
> +	int lanes = csis->num_data_lanes;
>  	u32 val;
>
>  	val = mipi_csis_read(csis, MIPI_CSIS_CMN_CTRL);
> @@ -1366,8 +1368,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
>  	}
>
>  	csis->bus = vep.bus.mipi_csi2;
> +	csis->num_data_lanes = csis->bus.num_data_lanes;
>
> -	dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
> +	dev_dbg(csis->dev, "max data lanes: %d\n", csis->bus.num_data_lanes);
>  	dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
>
>  	asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,
>
> --
> 2.43.0
>

Re: [PATCH v4 3/4] media: imx-mipi-csis: Store the number of data_lanes configured in dt

[Isaac Scott]

Hi Frank,

Thank you for your review!

Quoting Frank Li (2025-09-25 22:49:00)
> On Thu, Sep 25, 2025 at 04:54:28PM +0100, Isaac Scott wrote:
> > The number of active data lanes in use on a MIPI CSI2 bus is not
> > necessarily always the maximum. To allow us to configure the number of
> > data lanes actively in use, store the maximum to ensure we can configure
> > a number of data lanes that is supported.
> >
> 
> This patch just add num_data_lanes, and use csis->num_data_lanes instead
> of bus.num_data_lanes.
> 
> So commit message not reflect what you did
> 
> "
> media: imx-mipi-csis: Add num_data_lanes in mipi_csis_device
> 
> Add num_data_lanes field in mipi_csis_device, set equal to
> csis->bus.num_data_lanes. Prepare to support cases where the number of
> active data lanes differs from the maximum supported lanes.
> 
> No functional changes.
> "

Yes, that is much better, thank you for your suggestions (on this and
the next patch), I'll wait to see if there are any other comments and
improve my commit messages in the next version.

Best wishes,
Isaac

> 
> Frank
> 
> > Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
> > ---
> >  drivers/media/platform/nxp/imx-mipi-csis.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> > index 7c2a679dca2e..838a1ad123b5 100644
> > --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> > +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> > @@ -351,6 +351,8 @@ struct mipi_csis_device {
> >       u32 hs_settle;
> >       u32 clk_settle;
> >
> > +     unsigned int num_data_lanes;
> > +
> >       spinlock_t slock;       /* Protect events */
> >       struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
> >       struct dentry *debugfs_root;
> > @@ -573,7 +575,7 @@ static void mipi_csis_system_enable(struct mipi_csis_device *csis, int on)
> >       val = mipi_csis_read(csis, MIPI_CSIS_DPHY_CMN_CTRL);
> >       val &= ~MIPI_CSIS_DPHY_CMN_CTRL_ENABLE;
> >       if (on) {
> > -             mask = (1 << (csis->bus.num_data_lanes + 1)) - 1;
> > +             mask = (1 << (csis->num_data_lanes + 1)) - 1;
> >               val |= (mask & MIPI_CSIS_DPHY_CMN_CTRL_ENABLE);
> >       }
> >       mipi_csis_write(csis, MIPI_CSIS_DPHY_CMN_CTRL, val);
> > @@ -623,7 +625,7 @@ static int mipi_csis_calculate_params(struct mipi_csis_device *csis,
> >
> >       /* Calculate the line rate from the pixel rate. */
> >       link_freq = v4l2_get_link_freq(csis->source.pad, csis_fmt->width,
> > -                                    csis->bus.num_data_lanes * 2);
> > +                                    csis->num_data_lanes * 2);
> >       if (link_freq < 0) {
> >               dev_err(csis->dev, "Unable to obtain link frequency: %d\n",
> >                       (int)link_freq);
> > @@ -668,7 +670,7 @@ static void mipi_csis_set_params(struct mipi_csis_device *csis,
> >                                const struct v4l2_mbus_framefmt *format,
> >                                const struct csis_pix_format *csis_fmt)
> >  {
> > -     int lanes = csis->bus.num_data_lanes;
> > +     int lanes = csis->num_data_lanes;
> >       u32 val;
> >
> >       val = mipi_csis_read(csis, MIPI_CSIS_CMN_CTRL);
> > @@ -1366,8 +1368,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
> >       }
> >
> >       csis->bus = vep.bus.mipi_csi2;
> > +     csis->num_data_lanes = csis->bus.num_data_lanes;
> >
> > -     dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
> > +     dev_dbg(csis->dev, "max data lanes: %d\n", csis->bus.num_data_lanes);
> >       dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
> >
> >       asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,
> >
> > --
> > 2.43.0
> >

[PATCH v4 4/4] media: imx-mipi-csis: Get number of active lanes via mbus_config

[Isaac Scott]

The number of lanes actively used by a MIPI CSI transmitter may differ
from that which is defined in device tree, due to the source device not
using all of the connected data lanes on the board. As such, call on
v4l2_get_active_data_lanes() to check if the driver reports a differing
number of lanes to the maximum, and use that number of active lanes.

If the number of active data lanes is invalid, or the op is not
supported, use the maximum number of allowed data lanes.

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/platform/nxp/imx-mipi-csis.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
index 838a1ad123b5..637ef6e614fa 100644
--- a/drivers/media/platform/nxp/imx-mipi-csis.c
+++ b/drivers/media/platform/nxp/imx-mipi-csis.c
@@ -1034,6 +1034,10 @@ static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable)
 	format = v4l2_subdev_state_get_format(state, CSIS_PAD_SINK);
 	csis_fmt = find_csis_format(format->code);
 
+	ret = v4l2_get_active_data_lanes(csis->source.pad,
+					 csis->bus.num_data_lanes);
+	csis->num_data_lanes = ret < 0 ? csis->bus.num_data_lanes : ret;
+
 	ret = mipi_csis_calculate_params(csis, csis_fmt);
 	if (ret < 0)
 		goto err_unlock;

-- 
2.43.0

Re: [PATCH v4 4/4] media: imx-mipi-csis: Get number of active lanes via mbus_config

[Frank Li]

On Thu, Sep 25, 2025 at 04:54:29PM +0100, Isaac Scott wrote:
> The number of lanes actively used by a MIPI CSI transmitter may differ
> from that which is defined in device tree, due to the source device not
> using all of the connected data lanes on the board. As such, call on
> v4l2_get_active_data_lanes() to check if the driver reports a differing
> number of lanes to the maximum, and use that number of active lanes.
>
> If the number of active data lanes is invalid, or the op is not
> supported, use the maximum number of allowed data lanes.

Is below message better?

media: mipi-csis: Support active data lanes differing from maximum

Call v4l2_get_active_data_lanes() to get the number of lanes actively used
by the MIPI CSI transmitter, which may differs from the maximum defined in
the device tree.

If the driver reports an invalid number of active lanes, or the
operation is not supported, fall back to the maximum number of allowed
data lanes

Frank
>
> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index 838a1ad123b5..637ef6e614fa 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -1034,6 +1034,10 @@ static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable)
>  	format = v4l2_subdev_state_get_format(state, CSIS_PAD_SINK);
>  	csis_fmt = find_csis_format(format->code);
>
> +	ret = v4l2_get_active_data_lanes(csis->source.pad,
> +					 csis->bus.num_data_lanes);
> +	csis->num_data_lanes = ret < 0 ? csis->bus.num_data_lanes : ret;
> +
>  	ret = mipi_csis_calculate_params(csis, csis_fmt);
>  	if (ret < 0)
>  		goto err_unlock;
>
> --
> 2.43.0
>