linux-kernel - Re: [PATCH v5 2/5] i3c: add sysfs attribute for device NACK retry

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Message-ID: <aS9WNRyfRg9IUpna@lizhi-Precision-Tower-5810>
Date: Tue, 2 Dec 2025 16:12:21 -0500
From: Frank Li <Frank.li@....com>
To: adrianhoyin.ng@...era.com
Cc: alexandre.belloni@...tlin.com, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/5] i3c: add sysfs attribute for device NACK retry

On Tue, Dec 02, 2025 at 04:26:10PM +0800, adrianhoyin.ng@...era.com wrote:
> From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
>
> Add a `dev_nack_retry` sysfs attribute to allow reading and updating the
> device NACK retry count. A new `dev_nack_retry` field and an optional
> `set_dev_nack_retry()` callback are added to i3c_master_controller.
> The attribute is created only when the callback is implemented.
>
> Updates are applied under the I3C bus maintenance lock to ensure safe
> hardware reconfiguration.
>
> Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> ---
>  drivers/i3c/master.c       | 44 ++++++++++++++++++++++++++++++++++++++
>  include/linux/i3c/master.h |  2 ++
>  2 files changed, 46 insertions(+)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index d946db75df70..ab630c77b3c2 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -685,6 +685,44 @@ static ssize_t hotjoin_show(struct device *dev, struct device_attribute *da, cha
>
>  static DEVICE_ATTR_RW(hotjoin);
>
> +static ssize_t dev_nack_retry_show(struct device *dev, struct device_attribute *attr,
> +				   char *buf)
> +{
> +	struct i3c_bus *i3cbus = dev_to_i3cbus(dev);
> +
> +	return sysfs_emit(buf, "%u\n", i3cbus->cur_master->common.master->dev_nack_retry);
> +}
> +
> +static ssize_t dev_nack_retry_store(struct device *dev, struct device_attribute *attr,
> +				    const char *buf, size_t count)
> +{
> +	struct i3c_bus *i3cbus = dev_to_i3cbus(dev);
> +	struct i3c_master_controller *master;
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	master = i3cbus->cur_master->common.master;

why not use dev_to_i3cmaster() ?

> +
> +	if (i3cbus->cur_master->common.master->ops->set_dev_nack_retry) {

This file exist only if set_dev_nack_retry is not NULL. So needn't check
again here

> +		master->dev_nack_retry = val;
> +
> +		i3c_bus_maintenance_lock(i3cbus);
> +		ret = master->ops->set_dev_nack_retry(master);
> +		i3c_bus_maintenance_unlock(i3cbus);
> +	}
> +
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR_RW(dev_nack_retry);
> +
>  static struct attribute *i3c_masterdev_attrs[] = {
>  	&dev_attr_mode.attr,
>  	&dev_attr_current_master.attr,
> @@ -2962,6 +3000,9 @@ int i3c_master_register(struct i3c_master_controller *master,
>  	i3c_master_register_new_i3c_devs(master);
>  	i3c_bus_normaluse_unlock(&master->bus);
>
> +	if (master->ops->set_dev_nack_retry)
> +		device_create_file(&master->dev, &dev_attr_dev_nack_retry);
> +
>  	return 0;
>
>  err_del_dev:
> @@ -2987,6 +3028,9 @@ void i3c_master_unregister(struct i3c_master_controller *master)
>  {
>  	i3c_bus_notify(&master->bus, I3C_NOTIFY_BUS_REMOVE);
>
> +	if (master->ops->set_dev_nack_retry)
> +		device_remove_file(&master->dev, &dev_attr_dev_nack_retry);
> +
>  	i3c_master_i2c_adapter_cleanup(master);
>  	i3c_master_unregister_i3c_devs(master);
>  	i3c_master_bus_cleanup(master);
> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> index c52a82dd79a6..ccbc9a14bd6e 100644
> --- a/include/linux/i3c/master.h
> +++ b/include/linux/i3c/master.h
> @@ -491,6 +491,7 @@ struct i3c_master_controller_ops {
>  	int (*enable_hotjoin)(struct i3c_master_controller *master);
>  	int (*disable_hotjoin)(struct i3c_master_controller *master);
>  	int (*set_speed)(struct i3c_master_controller *master, enum i3c_open_drain_speed speed);
> +	int (*set_dev_nack_retry)(struct i3c_master_controller *master);

Need update kernel doc.

Frank

>  };
>
>  /**
> @@ -534,6 +535,7 @@ struct i3c_master_controller {
>  	} boardinfo;
>  	struct i3c_bus bus;
>  	struct workqueue_struct *wq;
> +	unsigned int dev_nack_retry;
>  };
>
>  /**
> --
> 2.49.GIT
>