Re: [PATCH] net: lantiq_etop: check the result of request_irq()

[Hauke Mehrtens]

On 12/21/20 7:04 PM, Andrew Lunn wrote:
> On Tue, Dec 22, 2020 at 12:59:08AM +0900, Masahiro Yamada wrote:
> > On Tue, Dec 22, 2020 at 12:26 AM Andrew Lunn <andrew@xxxxxxx> wrote:
> > > On Mon, Dec 21, 2020 at 02:43:23PM +0900, Masahiro Yamada wrote:
> > > > The declaration of request_irq() in <linux/interrupt.h> is marked as
> > > > __must_check.
> > > >
> > > > Without the return value check, I see the following warnings:
> > > >
> > > > drivers/net/ethernet/lantiq_etop.c: In function 'ltq_etop_hw_init':
> > > > drivers/net/ethernet/lantiq_etop.c:273:4: warning: ignoring return value of 'request_irq', declared with attribute warn_unused_result [-Wunused-result]
> > > >    273 |    request_irq(irq, ltq_etop_dma_irq, 0, "etop_tx", priv);
> > > >        |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > drivers/net/ethernet/lantiq_etop.c:281:4: warning: ignoring return value of 'request_irq', declared with attribute warn_unused_result [-Wunused-result]
> > > >    281 |    request_irq(irq, ltq_etop_dma_irq, 0, "etop_rx", priv);
> > > >        |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > Reported-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> > > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> > > > ---
> > > >
> > > >   drivers/net/ethernet/lantiq_etop.c | 13 +++++++++++--
> > > >   1 file changed, 11 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/lantiq_etop.c b/drivers/net/ethernet/lantiq_etop.c
> > > > index 2d0c52f7106b..960494f9752b 100644
> > > > --- a/drivers/net/ethernet/lantiq_etop.c
> > > > +++ b/drivers/net/ethernet/lantiq_etop.c
> > > > @@ -264,13 +264,18 @@ ltq_etop_hw_init(struct net_device *dev)
> > > >        for (i = 0; i < MAX_DMA_CHAN; i++) {
> > > >                int irq = LTQ_DMA_CH0_INT + i;
> > > >                struct ltq_etop_chan *ch = &priv->ch[i];
> > > > +             int ret;
> > > >
> > > >                ch->idx = ch->dma.nr = i;
> > > >                ch->dma.dev = &priv->pdev->dev;
> > > >
> > > >                if (IS_TX(i)) {
> > > >                        ltq_dma_alloc_tx(&ch->dma);
> > > > -                     request_irq(irq, ltq_etop_dma_irq, 0, "etop_tx", priv);
> > > > +                     ret = request_irq(irq, ltq_etop_dma_irq, 0, "etop_tx", priv);
> > > > +                     if (ret) {
> > > > +                             netdev_err(dev, "failed to request irq\n");
> > > > +                             return ret;
> > >
> > > You need to cleanup what ltq_dma_alloc_tx() did.
> >
> >
> > Any failure from this function will roll back
> > in the following paths:
> >
> >    ltq_etop_hw_exit()
> >       -> ltq_etop_free_channel()
> >            -> ltq_dma_free()
> >
> >
> > So, dma is freed anyway.
> >
> > One problem I see is,
> > ltq_etop_hw_exit() frees all DMA channels,
> > some of which may not have been allocated yet.
> >
> > If it is a bug, it is an existing bug.
> >
> >
> > > > +                     }
> > > >                } else if (IS_RX(i)) {
> > > >                        ltq_dma_alloc_rx(&ch->dma);
> > > >                        for (ch->dma.desc = 0; ch->dma.desc < LTQ_DESC_NUM;
> > > > @@ -278,7 +283,11 @@ ltq_etop_hw_init(struct net_device *dev)
> > > >                                if (ltq_etop_alloc_skb(ch))
> > > >                                        return -ENOMEM;
> >
> >
> > This -ENOMEM does not roll back anything here.
> >
> > As stated above, dma_free_coherent() is called.
> > The problem is, ltq_etop_hw_exit() rolls back too much.
> >
> > If your requirement is "this driver is completely wrong. Please rewrite it",
> > sorry, I cannot (unless I am paid to do so).
> >
> > I am just following this driver's roll-back model.
> >
> > Please do not expect more to a person who
> > volunteers to eliminate build warnings.
> >
> > Of course, if somebody volunteers to rewrite this driver correctly,
> > that is appreciated.
>
> Hi Hauke
>
> Do you still have this hardware? Do you have time to take a look at
> the cleanup code?
>
> Thanks
> 	Andrew

Hi Andrew,

I have this hardware somewhere at home, but I never made it work.
If I find some time I can have a loom at this problem in the next few weeks.

Hauke