linux-kernel - Re: [PATCH] driver core: bus: Return -EIO instead of 0 when show/store invalid bus attribute

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Message-ID: <2024072316-yeah-snide-ca28@gregkh>
Date: Tue, 23 Jul 2024 19:31:09 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org,
	Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH] driver core: bus: Return -EIO instead of 0 when
 show/store invalid bus attribute

On Tue, Jul 23, 2024 at 10:55:43PM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> Return -EIO instead of 0 when show/store invalid bus attribute as
> class/device/driver/kobject attribute.

Why?  What is this now going to break?  You are changing a user-visable
api that has been this way for 20+ years, how was this tested?

> 
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/base/bus.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index ffea0728b8b2..e84522a90102 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -152,7 +152,7 @@ static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
>  {
>  	struct bus_attribute *bus_attr = to_bus_attr(attr);
>  	struct subsys_private *subsys_priv = to_subsys_private(kobj);
> -	ssize_t ret = 0;
> +	ssize_t ret = -EIO;
>  
>  	if (bus_attr->show)
>  		ret = bus_attr->show(subsys_priv->bus, buf);
> @@ -164,7 +164,7 @@ static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
>  {
>  	struct bus_attribute *bus_attr = to_bus_attr(attr);
>  	struct subsys_private *subsys_priv = to_subsys_private(kobj);
> -	ssize_t ret = 0;
> +	ssize_t ret = -EIO;

Why -EIO?  What is wrong with returning an empty string?

I think I know why you picked this but you better document the heck out
of it AND test it very very well first.

thanks,

greg k-h