linux-kernel - Re: [PATCH v2] remoteproc: use %pe format string to print return error code

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Message-ID: <20211116162933.GA2318486@p14s>
Date:   Tue, 16 Nov 2021 09:29:33 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Mark-PK Tsai <mark-pk.tsai@...iatek.com>
Cc:     bjorn.andersson@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-remoteproc@...r.kernel.org, matthias.bgg@...il.com,
        ohad@...ery.com, yj.chiang@...iatek.com
Subject: Re: [PATCH v2] remoteproc: use %pe format string to print return
 error code

Good day,

On Tue, Nov 16, 2021 at 09:57:03PM +0800, Mark-PK Tsai wrote:
> > > > > Use %pe format string to print return error code which
> > > > > make the error message easier to understand.
> > > > >
> > > > > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@...iatek.com>
> > > > > ---
> > > > >  drivers/remoteproc/remoteproc_core.c | 4 ++--
> > > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > > > > index 502b6604b757..2242da320368 100644
> > > > > --- a/drivers/remoteproc/remoteproc_core.c
> > > > > +++ b/drivers/remoteproc/remoteproc_core.c
> > > > > @@ -575,8 +575,8 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
> > > > >                                            dma_get_mask(rproc->dev.parent));
> > > > >         if (ret) {
> > > > >                 dev_warn(dev,
> > > > > -                        "Failed to set DMA mask %llx. Trying to continue... %x\n",
> > > > > -                        dma_get_mask(rproc->dev.parent), ret);
> > > > > +                        "Failed to set DMA mask %llx. Trying to continue... (%pe)\n",
> > > > > +                        dma_get_mask(rproc->dev.parent), ERR_PTR(ret));
> > > >
> > > > Macro ERR_PTR() is used to convert error codes to pointer type when
> > > > returning from a function - I fail to see how doing so in a dev_warn()
> > > > context can make the message easier to understand.  Can you provide an
> > > > example?
> > >
> > > Hi,
> > >
> > > When dma_coerce_mask_and_coherent() fail, the output log will be as following.
> > >
> > > format          log
> > > %x              Trying to continue... fffffffb
> > > %d              Trying to continue... -5
> > > %pe             Trying to continue... -5        (if CONFIG_SYMBOLIC_ERRNAME is not set)
> > > %pe             Trying to continue... -EIO      (if CONFIG_SYMBOLIC_ERRNAME=y)
> >
> > When failing, functions dma_coerce_mask_and_coherent() returns -EIO.
> > Casting that to a (void *) with ERR_PTR() does not change that value.
> > Since variable @ret is already declared as "int" the real fix is to
> > change "%x" to "%d".
> 
> There're some other drivers do the same thing in the recent kernel, so I think
> it's fine to casting the `ret` to a (void *) for more user friendly.
> But I suppose it would depend on the maintainer's opinion.
> 
> So how about previous patch I sent, which also fix this issue by using %d.
> 
> https://lore.kernel.org/lkml/20211102120805.27137-1-mark-pk.tsai@mediatek.com/

I had not seen Russell's reply in the link you posted above.  I am not
completely sure about his solution but his insight and guidance in kernel
programming have precedence over mine.

I will take this patch.

Thanks,
Mathieu


>