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SubjectRe: [PATCH] uio: uio_pdrv_genirq V2
On Thu, Jul 10, 2008 at 08:56:39AM +0200, Uwe Kleine-König wrote:
> > +
> > +static irqreturn_t uio_pdrv_genirq_handler(int irq, struct uio_info *dev_info)
> > +{
> > + struct uio_pdrv_genirq_platdata *priv = dev_info->priv;
> > + unsigned long flags;
> > +
> > + /* Just disable the interrupt in the interrupt controller, and
> > + * remember the state so we can allow user space to enable it later.
> > + */
> > + spin_lock_irqsave(&priv->lock, flags);
> > + if (!priv->irq_disabled) {
> > + disable_irq_nosync(irq);
> > + priv->irq_disabled = 1;
> > + }
> > + spin_unlock_irqrestore(&priv->lock, flags);
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static int uio_pdrv_genirq_irqcontrol(struct uio_info *dev_info, s32 irq_on)
> > +{
> > + struct uio_pdrv_genirq_platdata *priv = dev_info->priv;
> > + unsigned long flags;
> > +
> > + /* Allow user space to enable and disable the interrupt
> > + * in the interrupt controller, but keep track of the
> > + * state to prevent per-irq depth damage.
> > + */
> > +
> > + spin_lock_irqsave(&priv->lock, flags);
> > + if (irq_on && priv->irq_disabled)
> > + enable_irq(dev_info->irq);
> > + else if (!irq_on && !priv->irq_disabled)
> > + disable_irq(dev_info->irq);
> I'm not sure if this is a problem on SMP. Should you use
> disable_irq_nosync here, too? Probably it's OK.

*_nosync should not be needed, as he doesn't call irqcontrol from the irq
handler. But using the same lock in handler and irqcontrol presents a
problem, as Alan pointed out.

>
> > +
> > + priv->irq_disabled = !irq_on;
> > + spin_unlock_irqrestore(&priv->lock, flags);
> > + return 0;
> > +}
>
>
> > + ret = uio_register_device(&pdev->dev, priv->uioinfo);
> > + if (ret) {
> > + dev_err(&pdev->dev, "unable to register uio device\n");
> > + goto bad1;
> > + }
> > +
> > + platform_set_drvdata(pdev, priv);
> This should probably go before uio_register_device. (Uups, this is an
> issue for uio_pdrv, too.)

Yes, because uio_register_device will enable the irq, and you might
arrive in the handler without having your platform data in place.

Thanks,
Hans

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