linux-kernel - Re: [PATCH v2 1/2] Drivers: hv: util: Don't force error code to ENODEV in util

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Message-ID: <20241209173056.GA1194@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Mon, 9 Dec 2024 09:30:56 -0800
From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To: Michael Kelley <mhklinux@...look.com>
Cc: "kys@...rosoft.com" <kys@...rosoft.com>,
	"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
	"wei.liu@...nel.org" <wei.liu@...nel.org>,
	"decui@...rosoft.com" <decui@...rosoft.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"vkuznets@...hat.com" <vkuznets@...hat.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] Drivers: hv: util: Don't force error code to
 ENODEV in util_probe()

On Sun, Dec 08, 2024 at 11:12:15PM +0000, Michael Kelley wrote:
> From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com> Sent: Sunday, December 8, 2024 9:31 AM
> > 
> > On Wed, Nov 06, 2024 at 07:42:46AM -0800, mhkelley58@...il.com wrote:
> > > From: Michael Kelley <mhklinux@...look.com>
> > >
> > > If the util_init function call in util_probe() returns an error code,
> > > util_probe() always return ENODEV, and the error code from the util_init
> > > function is lost. The error message output in the caller, vmbus_probe(),
> > > doesn't show the real error code.
> > >
> > > Fix this by just returning the error code from the util_init function.
> > > There doesn't seem to be a reason to force ENODEV, as other errors
> > > such as ENOMEM can already be returned from util_probe(). And the
> > > code in call_driver_probe() implies that ENODEV should mean that a
> > > matching driver wasn't found, which is not the case here.
> > >
> > > Suggested-by: Dexuan Cui <decui@...rosoft.com>
> > > Signed-off-by: Michael Kelley <mhklinux@...look.com>
> > > ---
> > > Changes in v2: None. This is the first version of Patch 1 of this series.
> > > The "v2" is due to changes to Patch 2 of the series.
> > >
> > >  drivers/hv/hv_util.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> > > index c4f525325790..370722220134 100644
> > > --- a/drivers/hv/hv_util.c
> > > +++ b/drivers/hv/hv_util.c
> > > @@ -590,10 +590,8 @@ static int util_probe(struct hv_device *dev,
> > >  	srv->channel = dev->channel;
> > >  	if (srv->util_init) {
> > >  		ret = srv->util_init(srv);
> > > -		if (ret) {
> > > -			ret = -ENODEV;
> > > +		if (ret)
> > >  			goto error1;
> > > -		}
> > 
> > After reviewing V2 of this series, I couldn’t find any scenario where
> > 'util_init' in any driver returns a value other than 0. 
> 
> Yeah, I noticed the same thing when doing this patch set.
> 
> > In such cases,
> > could we consider making all these functions 'void' ?
> > 
> > After this ee can remove the check for util_int return type.
> 
> I decided against making these changes. It seemed like code churn
> for not much benefit. And there's the possibility of some future
> change reintroducing an error code in one of the util_init functions,
> in which case we would need to put things back like they are now.
> Certainly this is a judgment call, but my take was to leave things
> as they are.
> 
> The changes you suggest would probably go as a third patch in
> the series. Wei Liu has already picked up the two patches as they
> are, so it would be fine to create an independent patch with the
> changes you suggest, if we want to go that route. My preference
> isn't that strong either way.

I realized later that the patch is already merged. I believe it's fine
to leave it as is unless someone feels motivated enough to push this change.

- Saurabh