The patch titled
genirq: introduce IRQF_ALLOW_NESTED flag for request_irq()
has been added to the -mm tree. Its filename is
genirq-introduce-irqf_allow_nested-flag-for-request_irq.patch
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Subject: genirq: introduce IRQF_ALLOW_NESTED flag for request_irq()
From: Marc Zyngier <maz@xxxxxxxxxxxxxxx>
Now that we enjoy threaded interrupts, we're starting to see irq_chip
implementations (wm831x, pca953x) that make use of threaded interrupts for
the controller, and nested interrupts for the client interrupt. It all
works very well, with one drawback:
Drivers requesting an IRQ must now know whether the handler will run in a
thread context of not, and call request_threaded_irq() or request_irq()
accordingly.
The problem is that the requesting driver sometimes doesn't know about the
nature of the interrupt, specially when the interrupt controller is a
discrete chip (typically a GPIO expander connected over I2C) that can be
connected to a wide variety of otherwise perfectly supported hardware.
The following patch introduces the IRQF_ALLOW_NESTED flag, that acts as a
"contract" between the driver and the genirq framework. By using this
flag as part of the request_irq() call, the driver informs the genirq
framework that the handler will happily run either in hardirq or nested
context, without any ill effect.
The benefit of this is a single API for drivers. It still requires the
driver to be audited, and the flag added to the request_irq() call.
Of course, this goes against Linus choice of having separate APIs for both
cases. The only alternative I can imagine for this is to use
request_threaded_irq() with the same function provided for both the
handler and the threaded handler. Ugly...
This patch has been tested on ARM and Blackfin platforms.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxxxxxxx>
Tested-by: Joachim Eastwood <joachim.eastwood@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/interrupt.h | 3 +++
kernel/irq/manage.c | 12 +++++++++---
2 files changed, 12 insertions(+), 3 deletions(-)
diff -puN include/linux/interrupt.h~genirq-introduce-irqf_allow_nested-flag-for-request_irq include/linux/interrupt.h
--- a/include/linux/interrupt.h~genirq-introduce-irqf_allow_nested-flag-for-request_irq
+++ a/include/linux/interrupt.h
@@ -52,6 +52,8 @@
* IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
* Used by threaded interrupts which need to keep the
* irq line disabled until the threaded handler has been run.
+ * IRQF_ALLOW_NESTED - Handler can be either run as hardirq or nested
+ * interrupt.
*/
#define IRQF_DISABLED 0x00000020
#define IRQF_SAMPLE_RANDOM 0x00000040
@@ -62,6 +64,7 @@
#define IRQF_NOBALANCING 0x00000800
#define IRQF_IRQPOLL 0x00001000
#define IRQF_ONESHOT 0x00002000
+#define IRQF_ALLOW_NESTED 0x00004000
/*
* Bits used by threaded handlers:
diff -puN kernel/irq/manage.c~genirq-introduce-irqf_allow_nested-flag-for-request_irq kernel/irq/manage.c
--- a/kernel/irq/manage.c~genirq-introduce-irqf_allow_nested-flag-for-request_irq
+++ a/kernel/irq/manage.c
@@ -641,12 +641,18 @@ __setup_irq(unsigned int irq, struct irq
/*
* Check whether the interrupt nests into another interrupt
- * thread.
+ * thread. Nested interrupt must provide a thread function
+ * unless it raises the IRQF_ALLOW_NESTED flag.
*/
nested = desc->status & IRQ_NESTED_THREAD;
if (nested) {
- if (!new->thread_fn)
- return -EINVAL;
+ if (!new->thread_fn) {
+ if (new->flags & IRQF_ALLOW_NESTED)
+ new->thread_fn = new->handler;
+ else
+ return -EINVAL;
+ }
+
/*
* Replace the primary handler which was provided from
* the driver for non nested interrupt handling by the
_
Patches currently in -mm which might be from maz@xxxxxxxxxxxxxxx are
linux-next.patch
genirq-introduce-irqf_allow_nested-flag-for-request_irq.patch
gpio-pca953xc-add-interrupt-handling-capability.patch
gpio-pca953xc-add-interrupt-handling-capability-fix.patch
gpio-pca953xc-add-interrupt-handling-capability-v4.patch
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