linux-kernel - Re: [PATCH v6 2/5] i3c: add sysfs attribute for device NACK retry

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aTCfQIWkZ4/U2U/6@lizhi-Precision-Tower-5810>
Date: Wed, 3 Dec 2025 15:36:16 -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 v6 2/5] i3c: add sysfs attribute for device NACK retry

On Wed, Dec 03, 2025 at 03:21:03PM +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       | 41 ++++++++++++++++++++++++++++++++++++++
>  include/linux/i3c/master.h |  5 +++++
>  2 files changed, 46 insertions(+)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index d946db75df70..e67f54c6e865 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -685,6 +685,41 @@ 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);

dev_to_i3cmaster(dev)->dev_nack_retry.

needn't i3cbus varaible.

> +}
> +
> +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 = dev_to_i3cmaster(dev);

you move it to top

struct i3c_master_controller *master = dev_to_i3cmaster(dev);

> +	master->dev_nack_retry = val;

save retry value after set_dev_nack_retry(), in case set_dev_nack_retry()
return failue. master->dev_nack_retry should keep previous correct value.

So you need add argument at set_dev_nack_retry(master, val).

Frank

> +
> +	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 +2997,9 @@ 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 +3025,9 @@ 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..ee254864c8d2 100644
> --- a/include/linux/i3c/master.h
> +++ b/include/linux/i3c/master.h
> @@ -462,6 +462,8 @@ struct i3c_bus {
>   * @enable_hotjoin: enable hot join event detect.
>   * @disable_hotjoin: disable hot join event detect.
>   * @set_speed: adjust I3C open drain mode timing.
> + * @set_dev_nack_retry: configure device NACK retry count for the master
> + *                      controller.
>   */
>  struct i3c_master_controller_ops {
>  	int (*bus_init)(struct i3c_master_controller *master);
> @@ -491,6 +493,7 @@ 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);
>  };
>
>  /**
> @@ -510,6 +513,7 @@ struct i3c_master_controller_ops {
>   * @boardinfo: board-level information attached to devices connected on the bus
>   * @bus: I3C bus exposed by this master
>   * @wq: workqueue which can be used by master
> + * @dev_nack_retry: retry count when slave device nack
>   *	drivers if they need to postpone operations that need to take place
>   *	in a thread context. Typical examples are Hot Join processing which
>   *	requires taking the bus lock in maintenance, which in turn, can only
> @@ -534,6 +538,7 @@ struct i3c_master_controller {
>  	} boardinfo;
>  	struct i3c_bus bus;
>  	struct workqueue_struct *wq;
> +	unsigned int dev_nack_retry;
>  };
>
>  /**
> --
> 2.49.GIT
>