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Date:   Tue, 11 Jul 2023 15:59:33 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Abhijit Gangurde <abhijit.gangurde@amd.com>
Cc:     linux-kernel@vger.kernel.org, Nipun.Gupta@amd.com,
        nikhil.agarwal@amd.com, puneet.gupta@amd.com, git@amd.com,
        michal.simek@amd.com,
        Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Subject: Re: [PATCH 2/4] cdx: add sysfs for reset_all
Message-ID: <2023071111-unreached-probation-45c5@gregkh>
References: <20230711121027.936487-1-abhijit.gangurde@amd.com>
 <20230711121027.936487-3-abhijit.gangurde@amd.com>
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On Tue, Jul 11, 2023 at 05:40:25PM +0530, Abhijit Gangurde wrote:
> Add sysfs for reset_all entry which resets all the
> devices on the CDX bus.

On all CDX busses, right?  Why all?  Why not per-bus?


> 
> Co-developed-by: Puneet Gupta <puneet.gupta@amd.com>
> Signed-off-by: Puneet Gupta <puneet.gupta@amd.com>
> Co-developed-by: Nipun Gupta <nipun.gupta@amd.com>
> Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
> Signed-off-by: Abhijit Gangurde <abhijit.gangurde@amd.com>
> Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
> Tested-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-cdx | 11 ++++++++++
>  drivers/cdx/cdx.c                       | 29 +++++++++++++++++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-cdx b/Documentation/ABI/testing/sysfs-bus-cdx
> index 0afa85b3c63b..d9e00058471d 100644
> --- a/Documentation/ABI/testing/sysfs-bus-cdx
> +++ b/Documentation/ABI/testing/sysfs-bus-cdx
> @@ -22,6 +22,17 @@ Description:
>  
>  		  # echo 0 > /sys/bus/cdx/enable
>  
> +What:		/sys/bus/cdx/reset_all
> +Date:		July 2023
> +Contact:	puneet.gupta@amd.com
> +Description:
> +		Writing y/1/on to this file resets all the devices
> +		present on the CDX bus
> +
> +		For example::
> +
> +		  # echo 1 > /sys/bus/cdx/reset_all

What does resetting a device mean will happen?

> +
>  What:		/sys/bus/cdx/devices/.../vendor
>  Date:		March 2023
>  Contact:	nipun.gupta@amd.com
> diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
> index 48c493a43491..4d20047b55bb 100644
> --- a/drivers/cdx/cdx.c
> +++ b/drivers/cdx/cdx.c
> @@ -106,6 +106,11 @@ int cdx_dev_reset(struct device *dev)
>  }
>  EXPORT_SYMBOL_GPL(cdx_dev_reset);
>  
> +static int reset_cdx_device(struct device *dev, void *data)
> +{
> +	return cdx_dev_reset(dev);
> +}
> +
>  /**
>   * cdx_unregister_device - Unregister a CDX device
>   * @dev: CDX device
> @@ -433,9 +438,33 @@ static ssize_t rescan_store(const struct bus_type *bus,
>  }
>  static BUS_ATTR_WO(rescan);
>  
> +static ssize_t reset_all_store(const struct bus_type *bus,
> +			       const char *buf, size_t count)
> +{
> +	bool val;
> +	int ret;
> +
> +	if (kstrtobool(buf, &val) < 0)
> +		return -EINVAL;
> +
> +	if (!val)
> +		return -EINVAL;
> +
> +	/* Reset all the devices attached to cdx bus */
> +	ret = bus_for_each_dev(bus, NULL, NULL, reset_cdx_device);

No locking needed?


> +	if (ret) {
> +		pr_err("error in CDX bus reset\n");

What error?  For what device?  Put the error message in the reset
callback, not here, as you have no idea what device failed.

thanks,

greg k-h