Re: [PATCH] net: broadcom: bcm4908enet: add platform_get_irq_byname error checking

Dan Carpenter
2022-09-13T10:52:32Z

On Mon, Sep 12, 2022 at 11:14:42AM -0700, Florian Fainelli wrote:
> On 9/12/22 04:29, Dan Carpenter wrote:
> > On Fri, Sep 09, 2022 at 02:25:45PM +0800, Yu Zhe wrote:
> > > The platform_get_irq_byname() function returns negative error codes on error,
> > > check it.
> > >
> > > Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
> > > ---
> > > drivers/net/ethernet/broadcom/bcm4908_enet.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/broadcom/bcm4908_enet.c b/drivers/net/ethernet/broadcom/bcm4908_enet.c
> > > index c131d8118489..d985056db6c2 100644
> > > --- a/drivers/net/ethernet/broadcom/bcm4908_enet.c
> > > +++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c
> > > @@ -705,6 +705,8 @@ static int bcm4908_enet_probe(struct platform_device *pdev)
> > > return netdev->irq;
> > > enet->irq_tx = platform_get_irq_byname(pdev, "tx");
> > > + if (enet->irq_tx < 0)
> > > + return enet->irq_tx;
> >
> > If you read the driver, then you will see that this is deliberate.
> > Search for irq_tx and read the comments. I'm not a subsystem expert so
> > I don't know if this an ideal way to write the code, but it's done
> > deliberately so please don't change it unless you can test it.
>
> Yup, the transmit interrupt is deemed optional, or at least was up to some
> point during the driver development. There is however a worthy bug you could
> fix:
>
> static int bcm4908_enet_stop(struct net_device *netdev)
> {
> struct bcm4908_enet *enet = netdev_priv(netdev);
> struct bcm4908_enet_dma_ring *tx_ring = &enet->tx_ring;
> struct bcm4908_enet_dma_ring *rx_ring = &enet->rx_ring;
>
> netif_stop_queue(netdev);
> netif_carrier_off(netdev);
> napi_disable(&rx_ring->napi);
> napi_disable(&tx_ring->napi);
>
> bcm4908_enet_dma_rx_ring_disable(enet, &enet->rx_ring);
> bcm4908_enet_dma_tx_ring_disable(enet, &enet->tx_ring);
>
> bcm4908_enet_dma_uninit(enet);
>
> free_irq(enet->irq_tx, enet);
>
> We might attempt to free an invalid interrupt here ^^

Freeing a negative IRQ does not cause an issue. The irq_to_desc()
function will return NULL so it becomes a no-op.

It's ugly code because you have to read in a couple different files to
verify that it works...