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

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Message-ID: <CANLsYkzsoXw8vCC-OBqHyQv216Rbjf9ZR7FuFK-zxC7gMzt9Kg@mail.gmail.com>
Date:   Fri, 12 Nov 2021 09:25:40 -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

On Thu, 11 Nov 2021 at 19:13, Mark-PK Tsai <mark-pk.tsai@...iatek.com> wrote:
>
> > Hi Mark,
> >
> >
> > >
> > > 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".