Messages in this thread | | | Date | Tue, 1 Sep 2009 13:43:11 -0700 | From | Andrew Morton <> | Subject | Re: [patch 2.6.31-rc7] gpiolib: allow poll() on value |
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On Thu, 27 Aug 2009 16:50:57 -0700 David Brownell <david-b@pacbell.net> wrote:
> From: Daniel Gl__ckner <dg@emlix.com> > Subject: [PATCH v3] gpiolib: allow poll(2) on gpio value > > Many gpio chips allow to generate interrupts when the value of a pin > changes. This patch gives usermode application the opportunity to make > use of this feature by calling poll(2) on the /sys/class/gpio/gpioN/value > sysfs file. The edge to trigger can be set in the edge file in the same > directory. Possible values are "none", "rising", "falling", and "both". > > Using level triggers is not possible with current sysfs since nothing > changes the GPIO value (and the IRQ keeps triggering). Edge triggering > will "just work". Note that if there was an event between read() and > poll(), the poll() returns immediately. > > Also note that this version only supports true GPIO interrupts. Some > later patch might be able to synthesize this behavior by timer-driven > polling; some systems seem to need that. > > ... > > +static struct idr pdesc_idr;
There's no locking to protect this tree. If that isn't a bug then I'd suggest that a comment be added here explaining why.
> +static irqreturn_t gpio_sysfs_irq(int irq, void *priv) > +{ > + struct work_struct *work = priv; > + > + schedule_work(work); > + return IRQ_HANDLED; > +}
The only place where we explicitly cancel the pending work is in gpio_setup_irq(). Is that sufficient? Is there any way in which the work callback can occur after things have been freed/closed/deinitialised/etc?
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