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

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Message-ID: <20211116135703.19432-1-mark-pk.tsai@mediatek.com>
Date:   Tue, 16 Nov 2021 21:57:03 +0800
From:   Mark-PK Tsai <mark-pk.tsai@...iatek.com>
To:     <mathieu.poirier@...aro.org>
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>, <mark-pk.tsai@...iatek.com>,
        <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

> > > > 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/