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include/hw/irq.h: New function qemu_irq_is_connected()

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Mostly devices don't need to care whether one of their output
qemu_irq lines is connected, because functions like qemu_set_irq()
silently do nothing if there is nothing on the other end.  However
sometimes a device might want to implement default behaviour for the
case where the machine hasn't wired the line up to anywhere.

Provide a function qemu_irq_is_connected() that devices can use for
this purpose.  (The test is trivial but encapsulating it in a
function makes it easier to see where we're doing it in case we need
to change the implementation later.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20200728103744.6909-2-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2020-08-03 17:55:03 +01:00
parent e7e5a9595a
commit faf7c6de34
1 changed files with 18 additions and 0 deletions
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18
include/hw/irq.h
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@ -55,4 +55,22 @@ qemu_irq qemu_irq_split(qemu_irq irq1, qemu_irq irq2);
on an existing vector of qemu_irq. */
void qemu_irq_intercept_in(qemu_irq *gpio_in, qemu_irq_handler handler, int n);
/**
* qemu_irq_is_connected: Return true if IRQ line is wired up
*
* If a qemu_irq has a device on the other (receiving) end of it,
* return true; otherwise return false.
*
* Usually device models don't need to care whether the machine model
* has wired up their outbound qemu_irq lines, because functions like
* qemu_set_irq() silently do nothing if there is nothing on the other
* end of the line. However occasionally a device model will want to
* provide default behaviour if its output is left floating, and
* it can use this function to identify when that is the case.
*/
static inline bool qemu_irq_is_connected(qemu_irq irq)
{
return irq != NULL;
}
#endif