[PATCH] genirq: add IRQF_NO_AUTOEN for request_irq

[Barry Song]

This patch originated from the discussion with Dmitry in the below thread:
https://lore.kernel.org/linux-input/20210102042902.41664-1-song.bao.hua@xxxxxxxxxxxxx/
there are many drivers which don't want interrupts enabled automatically
due to request_irq().
So they are handling this issue by either way of the below two:
(1)
irq_set_status_flags(irq, IRQ_NOAUTOEN);
request_irq(dev, irq...);
(2)
request_irq(dev, irq...);
disable_irq(irq);

The code in the second way is silly and unsafe. In the small time gap
between request_irq and disable_irq, interrupts can still come.
The code in the first way is safe though we might be able to do it in
the generic irq code.

I guess Dmitry also prefers genirq handles this as he said
"What I would like to see is to allow passing something like IRQF_DISABLED
to request_irq() so that we would not need neither irq_set_status_flags()
nor disable_irq()" in the original email thread.

If this one is accepted, hundreds of drivers with this problem will be
handled afterwards.

Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
---
 include/linux/interrupt.h |  3 +++
 kernel/irq/manage.c       |  3 +++
 kernel/irq/settings.h     | 10 ++++++++++
 3 files changed, 16 insertions(+)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index bb8ff9083e7d..0f22d277078c 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,8 @@
  *                interrupt handler after suspending interrupts. For system
  *                wakeup devices users need to implement wakeup detection in
  *                their interrupt handlers.
+ * IRQF_NO_AUTOEN - Don't enable IRQ automatically when users request it. Users
+ *                will enable it explicitly by enable_irq() later.
  */
 #define IRQF_SHARED		0x00000080
 #define IRQF_PROBE_SHARED	0x00000100
@@ -74,6 +76,7 @@
 #define IRQF_NO_THREAD		0x00010000
 #define IRQF_EARLY_RESUME	0x00020000
 #define IRQF_COND_SUSPEND	0x00040000
+#define IRQF_NO_AUTOEN		0x00080000
 
 #define IRQF_TIMER		(__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
 
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index ab8567f32501..364e8b47d9ba 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1693,6 +1693,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 			irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
 		}
 
+		if (new->flags & IRQF_NO_AUTOEN)
+			irq_settings_set_noautoen(desc);
+
 		if (irq_settings_can_autoenable(desc)) {
 			irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
 		} else {
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 403378b9947b..a28958a9c548 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -145,6 +145,16 @@ static inline bool irq_settings_can_move_pcntxt(struct irq_desc *desc)
 	return desc->status_use_accessors & _IRQ_MOVE_PCNTXT;
 }
 
+static inline void irq_settings_clr_noautoen(struct irq_desc *desc)
+{
+	desc->status_use_accessors &= ~_IRQ_NOAUTOEN;
+}
+
+static inline void irq_settings_set_noautoen(struct irq_desc *desc)
+{
+	desc->status_use_accessors |= _IRQ_NOAUTOEN;
+}
+
 static inline bool irq_settings_can_autoenable(struct irq_desc *desc)
 {
 	return !(desc->status_use_accessors & _IRQ_NOAUTOEN);
-- 
2.25.1