[PATCH v3 0/3] usb: usb251xb: support usage case without I2C control

[PATCH v3 0/3] usb: usb251xb: support usage case without I2C control

[Jisheng Zhang]

Currently, the usb251xb assumes i2c control. But from HW point of
view, the hub supports usage case without any i2c, we only want the
gpio controls.

Refactor the code so that register writes for configuration are only
performed if the device has a i2c_client provided and also register as
a platform driver. This allows the driver to be used to manage GPIO
based control of the device.

Since v2:
 - add usage example w/o i2c control in dt-binding
 - update commit msg
 - remove of_match_ptr

Since v1:
 - make the modern pm macros usage a separate patch
 - use pm_sleep_ptr instead of pm_ptr for usb251xb_plat_pm_ops, because
   this ops is for PM_SLEEP only.

Jisheng Zhang (3):
  dt-bindings: usb: usb251xb: support usage case without I2C control
  usb: usb251xb: use modern PM macros
  usb: usb251xb: support usage case without I2C control

 .../devicetree/bindings/usb/usb251xb.yaml     |   9 +-
 drivers/usb/misc/usb251xb.c                   | 108 +++++++++++++++---
 2 files changed, 102 insertions(+), 15 deletions(-)

-- 
2.50.0

[PATCH v3 1/3] dt-bindings: usb: usb251xb: support usage case without I2C control

[Jisheng Zhang]

Currently, the usb251xb assumes i2c control, and the corresponding
dt node looks like the following:

i2c {
	usb-hub@2c {
		compatible = "microchip,usb2512b";
		reg = <0x2c>;
		reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
	};
};

But from HW point of view, the hub supports usage case without any i2c
control, I.E we only want the gpio controls, for example the following
dt node:

usb-hub {
	compatible = "microchip,usb2512b";
	reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
};

Modify the dt-binding of usb2512b to support this usage case, and add
usage example to the examples section.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 Documentation/devicetree/bindings/usb/usb251xb.yaml | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/usb/usb251xb.yaml b/Documentation/devicetree/bindings/usb/usb251xb.yaml
index ac5b99710332..0329a6aaaa92 100644
--- a/Documentation/devicetree/bindings/usb/usb251xb.yaml
+++ b/Documentation/devicetree/bindings/usb/usb251xb.yaml
@@ -240,7 +240,6 @@ additionalProperties: false
 
 required:
   - compatible
-  - reg
 
 examples:
   - |
@@ -269,3 +268,11 @@ examples:
         swap-dx-lanes = <1 2>;
       };
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    usb-hub {
+      /* I2C is not connected */
+      compatible = "microchip,usb2512b";
+      reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
+    };
-- 
2.50.0

Re: [PATCH v3 1/3] dt-bindings: usb: usb251xb: support usage case without I2C control

[Krzysztof Kozlowski]

On Thu, Aug 21, 2025 at 12:17:41AM +0800, Jisheng Zhang wrote:
> Currently, the usb251xb assumes i2c control, and the corresponding
> dt node looks like the following:
> 
> i2c {
> 	usb-hub@2c {
> 		compatible = "microchip,usb2512b";
> 		reg = <0x2c>;
> 		reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
> 	};
> };

Above is redundant, obvious from stagtement that USB can be a device on
I2C bus. Just keep it simple.

> 
> But from HW point of view, the hub supports usage case without any i2c
> control, I.E we only want the gpio controls, for example the following
> dt node:
> 
> usb-hub {
> 	compatible = "microchip,usb2512b";
> 	reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
> };
> 
> Modify the dt-binding of usb2512b to support this usage case, and add
> usage example to the examples section.
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
>  Documentation/devicetree/bindings/usb/usb251xb.yaml | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

[PATCH v3 2/3] usb: usb251xb: use modern PM macros

[Jisheng Zhang]

Use the modern PM macros for the suspend and resume functions to be
automatically dropped by the compiler when CONFIG_PM or
CONFIG_PM_SLEEP are disabled, without having to use __maybe_unused.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 drivers/usb/misc/usb251xb.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
index 4fb453ca5450..cb2f946de42c 100644
--- a/drivers/usb/misc/usb251xb.c
+++ b/drivers/usb/misc/usb251xb.c
@@ -698,7 +698,7 @@ static int usb251xb_i2c_probe(struct i2c_client *i2c)
 	return usb251xb_probe(hub);
 }
 
-static int __maybe_unused usb251xb_suspend(struct device *dev)
+static int usb251xb_suspend(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct usb251xb *hub = i2c_get_clientdata(client);
@@ -706,7 +706,7 @@ static int __maybe_unused usb251xb_suspend(struct device *dev)
 	return regulator_disable(hub->vdd);
 }
 
-static int __maybe_unused usb251xb_resume(struct device *dev)
+static int usb251xb_resume(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct usb251xb *hub = i2c_get_clientdata(client);
@@ -719,7 +719,7 @@ static int __maybe_unused usb251xb_resume(struct device *dev)
 	return usb251xb_connect(hub);
 }
 
-static SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
+static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
 
 static const struct i2c_device_id usb251xb_id[] = {
 	{ "usb2422" },
@@ -739,7 +739,7 @@ static struct i2c_driver usb251xb_i2c_driver = {
 	.driver = {
 		.name = DRIVER_NAME,
 		.of_match_table = usb251xb_of_match,
-		.pm = &usb251xb_pm_ops,
+		.pm = pm_sleep_ptr(&usb251xb_pm_ops),
 	},
 	.probe = usb251xb_i2c_probe,
 	.id_table = usb251xb_id,
-- 
2.50.0

Re: [PATCH v3 2/3] usb: usb251xb: use modern PM macros

[Richard Leitner]

Hi Jisheng,

thanks for tackling this issue!

On Thu, Aug 21, 2025 at 12:17:42AM +0800, Jisheng Zhang wrote:
> Use the modern PM macros for the suspend and resume functions to be
> automatically dropped by the compiler when CONFIG_PM or
> CONFIG_PM_SLEEP are disabled, without having to use __maybe_unused.
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
>  drivers/usb/misc/usb251xb.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Reviewed-by: Richard Leitner <richard.leitner@linux.dev>

> 
> diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
> index 4fb453ca5450..cb2f946de42c 100644
> --- a/drivers/usb/misc/usb251xb.c
> +++ b/drivers/usb/misc/usb251xb.c
> @@ -698,7 +698,7 @@ static int usb251xb_i2c_probe(struct i2c_client *i2c)
>  	return usb251xb_probe(hub);
>  }
>  
> -static int __maybe_unused usb251xb_suspend(struct device *dev)
> +static int usb251xb_suspend(struct device *dev)
>  {
>  	struct i2c_client *client = to_i2c_client(dev);
>  	struct usb251xb *hub = i2c_get_clientdata(client);
> @@ -706,7 +706,7 @@ static int __maybe_unused usb251xb_suspend(struct device *dev)
>  	return regulator_disable(hub->vdd);
>  }
>  
> -static int __maybe_unused usb251xb_resume(struct device *dev)
> +static int usb251xb_resume(struct device *dev)
>  {
>  	struct i2c_client *client = to_i2c_client(dev);
>  	struct usb251xb *hub = i2c_get_clientdata(client);
> @@ -719,7 +719,7 @@ static int __maybe_unused usb251xb_resume(struct device *dev)
>  	return usb251xb_connect(hub);
>  }
>  
> -static SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
> +static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
>  
>  static const struct i2c_device_id usb251xb_id[] = {
>  	{ "usb2422" },
> @@ -739,7 +739,7 @@ static struct i2c_driver usb251xb_i2c_driver = {
>  	.driver = {
>  		.name = DRIVER_NAME,
>  		.of_match_table = usb251xb_of_match,
> -		.pm = &usb251xb_pm_ops,
> +		.pm = pm_sleep_ptr(&usb251xb_pm_ops),
>  	},
>  	.probe = usb251xb_i2c_probe,
>  	.id_table = usb251xb_id,
> -- 
> 2.50.0
> 

[PATCH v3 3/3] usb: usb251xb: support usage case without I2C control

[Jisheng Zhang]

Currently, the usb251xb assumes i2c control. But from HW point of
view, the hub supports usage case without any i2c, we only want the
gpio controls.

Refactor the code so that register writes for configuration are only
performed if the device has a i2c_client provided and also register as
a platform driver. This allows the driver to be used to manage GPIO
based control of the device.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 drivers/usb/misc/usb251xb.c | 108 +++++++++++++++++++++++++++++++-----
 1 file changed, 94 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
index cb2f946de42c..e9a9404d17b2 100644
--- a/drivers/usb/misc/usb251xb.c
+++ b/drivers/usb/misc/usb251xb.c
@@ -17,6 +17,7 @@
 #include <linux/module.h>
 #include <linux/nls.h>
 #include <linux/of.h>
+#include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 
@@ -242,15 +243,19 @@ static int usb251xb_check_dev_children(struct device *dev, void *child)
 static int usb251x_check_gpio_chip(struct usb251xb *hub)
 {
 	struct gpio_chip *gc = gpiod_to_chip(hub->gpio_reset);
-	struct i2c_adapter *adap = hub->i2c->adapter;
+	struct i2c_adapter *adap;
 	int ret;
 
+	if (!hub->i2c)
+		return 0;
+
 	if (!hub->gpio_reset)
 		return 0;
 
 	if (!gc)
 		return -EINVAL;
 
+	adap = hub->i2c->adapter;
 	ret = usb251xb_check_dev_children(&adap->dev, gc->parent);
 	if (ret) {
 		dev_err(hub->dev, "Reset GPIO chip is at the same i2c-bus\n");
@@ -271,7 +276,8 @@ static void usb251xb_reset(struct usb251xb *hub)
 	if (!hub->gpio_reset)
 		return;
 
-	i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
+	if (hub->i2c)
+		i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
 
 	gpiod_set_value_cansleep(hub->gpio_reset, 1);
 	usleep_range(1, 10);	/* >=1us RESET_N asserted */
@@ -280,7 +286,8 @@ static void usb251xb_reset(struct usb251xb *hub)
 	/* wait for hub recovery/stabilization */
 	usleep_range(500, 750);	/* >=500us after RESET_N deasserted */
 
-	i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
+	if (hub->i2c)
+		i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
 }
 
 static int usb251xb_connect(struct usb251xb *hub)
@@ -289,7 +296,11 @@ static int usb251xb_connect(struct usb251xb *hub)
 	int err, i;
 	char i2c_wb[USB251XB_I2C_REG_SZ];
 
-	memset(i2c_wb, 0, USB251XB_I2C_REG_SZ);
+	if (!hub->i2c) {
+		usb251xb_reset(hub);
+		dev_info(dev, "hub is put in default configuration.\n");
+		return 0;
+	}
 
 	if (hub->skip_config) {
 		dev_info(dev, "Skip hub configuration, only attach.\n");
@@ -698,18 +709,13 @@ static int usb251xb_i2c_probe(struct i2c_client *i2c)
 	return usb251xb_probe(hub);
 }
 
-static int usb251xb_suspend(struct device *dev)
+static int usb251xb_suspend(struct usb251xb *hub)
 {
-	struct i2c_client *client = to_i2c_client(dev);
-	struct usb251xb *hub = i2c_get_clientdata(client);
-
 	return regulator_disable(hub->vdd);
 }
 
-static int usb251xb_resume(struct device *dev)
+static int usb251xb_resume(struct usb251xb *hub)
 {
-	struct i2c_client *client = to_i2c_client(dev);
-	struct usb251xb *hub = i2c_get_clientdata(client);
 	int err;
 
 	err = regulator_enable(hub->vdd);
@@ -719,7 +725,23 @@ static int usb251xb_resume(struct device *dev)
 	return usb251xb_connect(hub);
 }
 
-static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
+static int usb251xb_i2c_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct usb251xb *hub = i2c_get_clientdata(client);
+
+	return usb251xb_suspend(hub);
+}
+
+static int usb251xb_i2c_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct usb251xb *hub = i2c_get_clientdata(client);
+
+	return usb251xb_resume(hub);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_i2c_pm_ops, usb251xb_i2c_suspend, usb251xb_i2c_resume);
 
 static const struct i2c_device_id usb251xb_id[] = {
 	{ "usb2422" },
@@ -739,13 +761,71 @@ static struct i2c_driver usb251xb_i2c_driver = {
 	.driver = {
 		.name = DRIVER_NAME,
 		.of_match_table = usb251xb_of_match,
-		.pm = pm_sleep_ptr(&usb251xb_pm_ops),
+		.pm = pm_sleep_ptr(&usb251xb_i2c_pm_ops),
 	},
 	.probe = usb251xb_i2c_probe,
 	.id_table = usb251xb_id,
 };
 
-module_i2c_driver(usb251xb_i2c_driver);
+static int usb251xb_plat_probe(struct platform_device *pdev)
+{
+	struct usb251xb *hub;
+
+	hub = devm_kzalloc(&pdev->dev, sizeof(*hub), GFP_KERNEL);
+	if (!hub)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, hub);
+	hub->dev = &pdev->dev;
+
+	return usb251xb_probe(hub);
+}
+
+static int usb251xb_plat_suspend(struct device *dev)
+{
+	return usb251xb_suspend(dev_get_drvdata(dev));
+}
+
+static int usb251xb_plat_resume(struct device *dev)
+{
+	return usb251xb_resume(dev_get_drvdata(dev));
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_plat_pm_ops, usb251xb_plat_suspend, usb251xb_plat_resume);
+
+static struct platform_driver usb251xb_plat_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = usb251xb_of_match,
+		.pm = pm_sleep_ptr(&usb251xb_plat_pm_ops),
+	},
+	.probe		= usb251xb_plat_probe,
+};
+
+static int __init usb251xb_init(void)
+{
+	int err;
+
+	err = i2c_add_driver(&usb251xb_i2c_driver);
+	if (err)
+		return err;
+
+	err = platform_driver_register(&usb251xb_plat_driver);
+	if (err) {
+		i2c_del_driver(&usb251xb_i2c_driver);
+		return err;
+	}
+
+	return 0;
+}
+module_init(usb251xb_init);
+
+static void __exit usb251xb_exit(void)
+{
+	platform_driver_unregister(&usb251xb_plat_driver);
+	i2c_del_driver(&usb251xb_i2c_driver);
+}
+module_exit(usb251xb_exit);
 
 MODULE_AUTHOR("Richard Leitner <richard.leitner@skidata.com>");
 MODULE_DESCRIPTION("USB251x/xBi USB 2.0 Hub Controller Driver");
-- 
2.50.0

Re: [PATCH v3 3/3] usb: usb251xb: support usage case without I2C control

[Richard Leitner]

Hi Jisheng,

On Thu, Aug 21, 2025 at 12:17:43AM +0800, Jisheng Zhang wrote:
> Currently, the usb251xb assumes i2c control. But from HW point of
> view, the hub supports usage case without any i2c, we only want the
> gpio controls.
> 
> Refactor the code so that register writes for configuration are only
> performed if the device has a i2c_client provided and also register as
> a platform driver. This allows the driver to be used to manage GPIO
> based control of the device.
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
>  drivers/usb/misc/usb251xb.c | 108 +++++++++++++++++++++++++++++++-----
>  1 file changed, 94 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
> index cb2f946de42c..e9a9404d17b2 100644
> --- a/drivers/usb/misc/usb251xb.c
> +++ b/drivers/usb/misc/usb251xb.c
> @@ -17,6 +17,7 @@
>  #include <linux/module.h>
>  #include <linux/nls.h>
>  #include <linux/of.h>
> +#include <linux/platform_device.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/slab.h>
>  
> @@ -242,15 +243,19 @@ static int usb251xb_check_dev_children(struct device *dev, void *child)
>  static int usb251x_check_gpio_chip(struct usb251xb *hub)
>  {
>  	struct gpio_chip *gc = gpiod_to_chip(hub->gpio_reset);
> -	struct i2c_adapter *adap = hub->i2c->adapter;
> +	struct i2c_adapter *adap;
>  	int ret;
>  
> +	if (!hub->i2c)
> +		return 0;
> +
>  	if (!hub->gpio_reset)
>  		return 0;
>  
>  	if (!gc)
>  		return -EINVAL;
>  
> +	adap = hub->i2c->adapter;
>  	ret = usb251xb_check_dev_children(&adap->dev, gc->parent);
>  	if (ret) {
>  		dev_err(hub->dev, "Reset GPIO chip is at the same i2c-bus\n");
> @@ -271,7 +276,8 @@ static void usb251xb_reset(struct usb251xb *hub)
>  	if (!hub->gpio_reset)
>  		return;
>  
> -	i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> +	if (hub->i2c)
> +		i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
>  
>  	gpiod_set_value_cansleep(hub->gpio_reset, 1);
>  	usleep_range(1, 10);	/* >=1us RESET_N asserted */
> @@ -280,7 +286,8 @@ static void usb251xb_reset(struct usb251xb *hub)
>  	/* wait for hub recovery/stabilization */
>  	usleep_range(500, 750);	/* >=500us after RESET_N deasserted */
>  
> -	i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> +	if (hub->i2c)
> +		i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
>  }
>  
>  static int usb251xb_connect(struct usb251xb *hub)
> @@ -289,7 +296,11 @@ static int usb251xb_connect(struct usb251xb *hub)
>  	int err, i;
>  	char i2c_wb[USB251XB_I2C_REG_SZ];
>  
> -	memset(i2c_wb, 0, USB251XB_I2C_REG_SZ);
> +	if (!hub->i2c) {
> +		usb251xb_reset(hub);
> +		dev_info(dev, "hub is put in default configuration.\n");
> +		return 0;
> +	}

You dropped the memset of write buffer. Are you sure this doesn't cause
any issues? (Sorry, I'm currently travelling, so I wasn't able to test
the series on real hw)

Apart from that the patch LGTM. Thanks! :-)

>  
>  	if (hub->skip_config) {
>  		dev_info(dev, "Skip hub configuration, only attach.\n");
> @@ -698,18 +709,13 @@ static int usb251xb_i2c_probe(struct i2c_client *i2c)
>  	return usb251xb_probe(hub);
>  }
>  
> -static int usb251xb_suspend(struct device *dev)
> +static int usb251xb_suspend(struct usb251xb *hub)
>  {
> -	struct i2c_client *client = to_i2c_client(dev);
> -	struct usb251xb *hub = i2c_get_clientdata(client);
> -
>  	return regulator_disable(hub->vdd);
>  }
>  
> -static int usb251xb_resume(struct device *dev)
> +static int usb251xb_resume(struct usb251xb *hub)
>  {
> -	struct i2c_client *client = to_i2c_client(dev);
> -	struct usb251xb *hub = i2c_get_clientdata(client);
>  	int err;
>  
>  	err = regulator_enable(hub->vdd);
> @@ -719,7 +725,23 @@ static int usb251xb_resume(struct device *dev)
>  	return usb251xb_connect(hub);
>  }
>  
> -static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
> +static int usb251xb_i2c_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct usb251xb *hub = i2c_get_clientdata(client);
> +
> +	return usb251xb_suspend(hub);
> +}
> +
> +static int usb251xb_i2c_resume(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct usb251xb *hub = i2c_get_clientdata(client);
> +
> +	return usb251xb_resume(hub);
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_i2c_pm_ops, usb251xb_i2c_suspend, usb251xb_i2c_resume);
>  
>  static const struct i2c_device_id usb251xb_id[] = {
>  	{ "usb2422" },
> @@ -739,13 +761,71 @@ static struct i2c_driver usb251xb_i2c_driver = {
>  	.driver = {
>  		.name = DRIVER_NAME,
>  		.of_match_table = usb251xb_of_match,
> -		.pm = pm_sleep_ptr(&usb251xb_pm_ops),
> +		.pm = pm_sleep_ptr(&usb251xb_i2c_pm_ops),
>  	},
>  	.probe = usb251xb_i2c_probe,
>  	.id_table = usb251xb_id,
>  };
>  
> -module_i2c_driver(usb251xb_i2c_driver);
> +static int usb251xb_plat_probe(struct platform_device *pdev)
> +{
> +	struct usb251xb *hub;
> +
> +	hub = devm_kzalloc(&pdev->dev, sizeof(*hub), GFP_KERNEL);
> +	if (!hub)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, hub);
> +	hub->dev = &pdev->dev;
> +
> +	return usb251xb_probe(hub);
> +}
> +
> +static int usb251xb_plat_suspend(struct device *dev)
> +{
> +	return usb251xb_suspend(dev_get_drvdata(dev));
> +}
> +
> +static int usb251xb_plat_resume(struct device *dev)
> +{
> +	return usb251xb_resume(dev_get_drvdata(dev));
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_plat_pm_ops, usb251xb_plat_suspend, usb251xb_plat_resume);
> +
> +static struct platform_driver usb251xb_plat_driver = {
> +	.driver = {
> +		.name = DRIVER_NAME,
> +		.of_match_table = usb251xb_of_match,
> +		.pm = pm_sleep_ptr(&usb251xb_plat_pm_ops),
> +	},
> +	.probe		= usb251xb_plat_probe,
> +};
> +
> +static int __init usb251xb_init(void)
> +{
> +	int err;
> +
> +	err = i2c_add_driver(&usb251xb_i2c_driver);
> +	if (err)
> +		return err;
> +
> +	err = platform_driver_register(&usb251xb_plat_driver);
> +	if (err) {
> +		i2c_del_driver(&usb251xb_i2c_driver);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +module_init(usb251xb_init);
> +
> +static void __exit usb251xb_exit(void)
> +{
> +	platform_driver_unregister(&usb251xb_plat_driver);
> +	i2c_del_driver(&usb251xb_i2c_driver);
> +}
> +module_exit(usb251xb_exit);
>  
>  MODULE_AUTHOR("Richard Leitner <richard.leitner@skidata.com>");
>  MODULE_DESCRIPTION("USB251x/xBi USB 2.0 Hub Controller Driver");
> -- 
> 2.50.0
> 

regards;rl

Re: [PATCH v3 3/3] usb: usb251xb: support usage case without I2C control

[Jisheng Zhang]

On Sun, Aug 24, 2025 at 08:55:09PM +0200, Richard Leitner wrote:
> Hi Jisheng,
> 
> On Thu, Aug 21, 2025 at 12:17:43AM +0800, Jisheng Zhang wrote:
> > Currently, the usb251xb assumes i2c control. But from HW point of
> > view, the hub supports usage case without any i2c, we only want the
> > gpio controls.
> > 
> > Refactor the code so that register writes for configuration are only
> > performed if the device has a i2c_client provided and also register as
> > a platform driver. This allows the driver to be used to manage GPIO
> > based control of the device.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> >  drivers/usb/misc/usb251xb.c | 108 +++++++++++++++++++++++++++++++-----
> >  1 file changed, 94 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
> > index cb2f946de42c..e9a9404d17b2 100644
> > --- a/drivers/usb/misc/usb251xb.c
> > +++ b/drivers/usb/misc/usb251xb.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/module.h>
> >  #include <linux/nls.h>
> >  #include <linux/of.h>
> > +#include <linux/platform_device.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/slab.h>
> >  
> > @@ -242,15 +243,19 @@ static int usb251xb_check_dev_children(struct device *dev, void *child)
> >  static int usb251x_check_gpio_chip(struct usb251xb *hub)
> >  {
> >  	struct gpio_chip *gc = gpiod_to_chip(hub->gpio_reset);
> > -	struct i2c_adapter *adap = hub->i2c->adapter;
> > +	struct i2c_adapter *adap;
> >  	int ret;
> >  
> > +	if (!hub->i2c)
> > +		return 0;
> > +
> >  	if (!hub->gpio_reset)
> >  		return 0;
> >  
> >  	if (!gc)
> >  		return -EINVAL;
> >  
> > +	adap = hub->i2c->adapter;
> >  	ret = usb251xb_check_dev_children(&adap->dev, gc->parent);
> >  	if (ret) {
> >  		dev_err(hub->dev, "Reset GPIO chip is at the same i2c-bus\n");
> > @@ -271,7 +276,8 @@ static void usb251xb_reset(struct usb251xb *hub)
> >  	if (!hub->gpio_reset)
> >  		return;
> >  
> > -	i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> > +	if (hub->i2c)
> > +		i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> >  
> >  	gpiod_set_value_cansleep(hub->gpio_reset, 1);
> >  	usleep_range(1, 10);	/* >=1us RESET_N asserted */
> > @@ -280,7 +286,8 @@ static void usb251xb_reset(struct usb251xb *hub)
> >  	/* wait for hub recovery/stabilization */
> >  	usleep_range(500, 750);	/* >=500us after RESET_N deasserted */
> >  
> > -	i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> > +	if (hub->i2c)
> > +		i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> >  }
> >  
> >  static int usb251xb_connect(struct usb251xb *hub)
> > @@ -289,7 +296,11 @@ static int usb251xb_connect(struct usb251xb *hub)
> >  	int err, i;
> >  	char i2c_wb[USB251XB_I2C_REG_SZ];
> >  
> > -	memset(i2c_wb, 0, USB251XB_I2C_REG_SZ);
> > +	if (!hub->i2c) {
> > +		usb251xb_reset(hub);
> > +		dev_info(dev, "hub is put in default configuration.\n");
> > +		return 0;
> > +	}
> 
> You dropped the memset of write buffer. Are you sure this doesn't cause
> any issues? (Sorry, I'm currently travelling, so I wasn't able to test
> the series on real hw)

oops, good catch! Even if the removing memset() works it should be in a
seperate patch. I will send v2 soon. Thanks for your review!

> 
> Apart from that the patch LGTM. Thanks! :-)
> 
> >  
> >  	if (hub->skip_config) {
> >  		dev_info(dev, "Skip hub configuration, only attach.\n");
> > @@ -698,18 +709,13 @@ static int usb251xb_i2c_probe(struct i2c_client *i2c)
> >  	return usb251xb_probe(hub);
> >  }
> >  
> > -static int usb251xb_suspend(struct device *dev)
> > +static int usb251xb_suspend(struct usb251xb *hub)
> >  {
> > -	struct i2c_client *client = to_i2c_client(dev);
> > -	struct usb251xb *hub = i2c_get_clientdata(client);
> > -
> >  	return regulator_disable(hub->vdd);
> >  }
> >  
> > -static int usb251xb_resume(struct device *dev)
> > +static int usb251xb_resume(struct usb251xb *hub)
> >  {
> > -	struct i2c_client *client = to_i2c_client(dev);
> > -	struct usb251xb *hub = i2c_get_clientdata(client);
> >  	int err;
> >  
> >  	err = regulator_enable(hub->vdd);
> > @@ -719,7 +725,23 @@ static int usb251xb_resume(struct device *dev)
> >  	return usb251xb_connect(hub);
> >  }
> >  
> > -static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_pm_ops, usb251xb_suspend, usb251xb_resume);
> > +static int usb251xb_i2c_suspend(struct device *dev)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	struct usb251xb *hub = i2c_get_clientdata(client);
> > +
> > +	return usb251xb_suspend(hub);
> > +}
> > +
> > +static int usb251xb_i2c_resume(struct device *dev)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	struct usb251xb *hub = i2c_get_clientdata(client);
> > +
> > +	return usb251xb_resume(hub);
> > +}
> > +
> > +static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_i2c_pm_ops, usb251xb_i2c_suspend, usb251xb_i2c_resume);
> >  
> >  static const struct i2c_device_id usb251xb_id[] = {
> >  	{ "usb2422" },
> > @@ -739,13 +761,71 @@ static struct i2c_driver usb251xb_i2c_driver = {
> >  	.driver = {
> >  		.name = DRIVER_NAME,
> >  		.of_match_table = usb251xb_of_match,
> > -		.pm = pm_sleep_ptr(&usb251xb_pm_ops),
> > +		.pm = pm_sleep_ptr(&usb251xb_i2c_pm_ops),
> >  	},
> >  	.probe = usb251xb_i2c_probe,
> >  	.id_table = usb251xb_id,
> >  };
> >  
> > -module_i2c_driver(usb251xb_i2c_driver);
> > +static int usb251xb_plat_probe(struct platform_device *pdev)
> > +{
> > +	struct usb251xb *hub;
> > +
> > +	hub = devm_kzalloc(&pdev->dev, sizeof(*hub), GFP_KERNEL);
> > +	if (!hub)
> > +		return -ENOMEM;
> > +
> > +	platform_set_drvdata(pdev, hub);
> > +	hub->dev = &pdev->dev;
> > +
> > +	return usb251xb_probe(hub);
> > +}
> > +
> > +static int usb251xb_plat_suspend(struct device *dev)
> > +{
> > +	return usb251xb_suspend(dev_get_drvdata(dev));
> > +}
> > +
> > +static int usb251xb_plat_resume(struct device *dev)
> > +{
> > +	return usb251xb_resume(dev_get_drvdata(dev));
> > +}
> > +
> > +static DEFINE_SIMPLE_DEV_PM_OPS(usb251xb_plat_pm_ops, usb251xb_plat_suspend, usb251xb_plat_resume);
> > +
> > +static struct platform_driver usb251xb_plat_driver = {
> > +	.driver = {
> > +		.name = DRIVER_NAME,
> > +		.of_match_table = usb251xb_of_match,
> > +		.pm = pm_sleep_ptr(&usb251xb_plat_pm_ops),
> > +	},
> > +	.probe		= usb251xb_plat_probe,
> > +};
> > +
> > +static int __init usb251xb_init(void)
> > +{
> > +	int err;
> > +
> > +	err = i2c_add_driver(&usb251xb_i2c_driver);
> > +	if (err)
> > +		return err;
> > +
> > +	err = platform_driver_register(&usb251xb_plat_driver);
> > +	if (err) {
> > +		i2c_del_driver(&usb251xb_i2c_driver);
> > +		return err;
> > +	}
> > +
> > +	return 0;
> > +}
> > +module_init(usb251xb_init);
> > +
> > +static void __exit usb251xb_exit(void)
> > +{
> > +	platform_driver_unregister(&usb251xb_plat_driver);
> > +	i2c_del_driver(&usb251xb_i2c_driver);
> > +}
> > +module_exit(usb251xb_exit);
> >  
> >  MODULE_AUTHOR("Richard Leitner <richard.leitner@skidata.com>");
> >  MODULE_DESCRIPTION("USB251x/xBi USB 2.0 Hub Controller Driver");
> > -- 
> > 2.50.0
> > 
> 
> regards;rl