linux-kernel - Re: [PATCH v2] driver core: bus: Remove an impossible error handling path in bus_add

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Message-ID: <2024101316-designing-renegade-6f00@gregkh>
Date: Sun, 13 Oct 2024 17:02:43 +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 v2] driver core: bus: Remove an impossible error handling
 path in bus_add_driver()

On Tue, Sep 17, 2024 at 02:53:32PM +0800, Zijun Hu wrote:
> On 2024/9/17 14:49, Zijun Hu wrote:
> > From: Zijun Hu <quic_zijuhu@...cinc.com>
> > 
> > For the following function call chain:
> > API driver_register() -> bus_add_driver() -> driver_attach()
> > 
> > There is an error handling path for driver_attach() returning non-zero
> > or failure in bus_add_driver(), remove it with below reasons:
> > 
> > - It is impossible for driver_attach() to have failure in bus_add_driver()
> >   For int driver_attach(const struct device_driver *drv), the only factor
> >   which makes it failed is that bus_to_subsys(@drv->bus) is NULL, but
> >   the factor has been excluded by bus_add_driver() before calling it.
> > 
> > - driver_attach() is irrelevant with driver_register(), so the former's
> >   result should not also have an impact on the later.
> > 
> > Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> > ---
> > Changes in v2:
> > - Remove the error handling path instead of WARN_ON() it.
> > - Correct title and commit message
> > - Link to v1: https://lore.kernel.org/r/20240915-bus_add_driver_fix-v1-1-ce5cf1f66601@quicinc.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 657c93c38b0d..54ff92aece92 100644
> > --- a/drivers/base/bus.c
> > +++ b/drivers/base/bus.c
> > @@ -674,7 +674,8 @@ int bus_add_driver(struct device_driver *drv)
> >  	if (sp->drivers_autoprobe) {
> >  		error = driver_attach(drv);
> >  		if (error)
> > -			goto out_del_list;
> > +			pr_warn("%s: failed to attach driver '%s' to bus '%s'\n",
> > +				__func__, drv->name, sp->bus->name);
> 
> driver_attach() has __must_check attribute and this error may be
> inconsequential for driver_register(), so give pr_warn() here

Yes, but you  now ignore the error, so someone will come back and add
that error handling in.  I'd just leave it as-is.

thanks,

greg k-h