On Mon, 17 Dec 2012 16:11:22 +0100
Marcos Lois Bermúdez <marcos.disca...@gmail.com> wrote:
> For my understand if i call for example:
>
> request_threaded_irq(irqmum, NULL, irq_handle, IRQF_TRIGGER_FALLING,
> DEVICE_NAME, priv);
>
> This seem to make a old Hard IRQ handler, and inside of this handler
> sleep APIs can't be used, but i see some SPI drivers that seem to
> register a IRQ of this form and make API calls that can sleep in the
> handler.
Not quite. The prototype for request_threaded_irq() is:
int request_threaded_irq(unsigned int irq, irq_handler_t handler,
irq_handler_t thread_fn, unsigned long irqflags,
const char *devname, void *dev_id)
Note the presents of *two* handlers, called "handler" and "thread_fn".
The first, "handler", is called in interrupt context; it's job is usually
to quiet the device and return; it cannot sleep. If it's return value is
IRQ_WAKE_THREAD, the thread_fn() will be called in process context; it
*can* sleep. In the example you cite, there is no immediate handler, only
the thread_fn(); the call to a blocking function from within the
thread_fn() is correct.
Hope that helps,
jon
Jonathan Corbet / LWN.net / cor...@lwn.net
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