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Subject[PATCH 1/1] genirq: Fix [devm_]irq_alloc_desc returning irq 0
Date
Since commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0
is invalid"), having a linux-irq with number 0 will trigger a WARN
when calling platform_get_irq*() to retrieve that linux-irq.

Since [devm_]irq_alloc_desc allocs 1 single irq and since irq 0 is
normally not used, it would return 0 before this commit, triggering
that WARN. This happens e.g. on Intel Bay Trail and Cherry Trail
devices using the LPE audio engine for HDMI audio:

[ 22.761392] ------------[ cut here ]------------
[ 22.761405] 0 is an invalid IRQ number
[ 22.761462] WARNING: CPU: 3 PID: 472 at drivers/base/platform.c:238 platform_get_irq_optional+0x108/0x180
[ 22.761470] Modules linked in: snd_hdmi_lpe_audio(+) ...
...
[ 22.762133] Call Trace:
[ 22.762158] platform_get_irq+0x17/0x30
[ 22.762182] hdmi_lpe_audio_probe+0x4a/0x6c0 [snd_hdmi_lpe_audio]
...
[ 22.762726] ---[ end trace ceece38854223a0b ]---

Change the 'from' parameter passed to __[devm_]irq_alloc_descs() by the
[devm_]irq_alloc_desc macros from 0 to 1, so that these macros
will no longer return 0.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
A quick grep for 'irq_alloc_desc\(' shows only 2 users of irq_alloc_desc():
1. drivers/gpu/drm/i915/display/intel_lpe_audio.c
2. drivers/sh/intc/virq.c
But that might very well be an incomplete list.
---
include/linux/irq.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 4aeb1c4c7e07..2efde6a79b7e 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -928,7 +928,7 @@ int __devm_irq_alloc_descs(struct device *dev, int irq, unsigned int from,
__irq_alloc_descs(irq, from, cnt, node, THIS_MODULE, NULL)

#define irq_alloc_desc(node) \
- irq_alloc_descs(-1, 0, 1, node)
+ irq_alloc_descs(-1, 1, 1, node)

#define irq_alloc_desc_at(at, node) \
irq_alloc_descs(at, at, 1, node)
@@ -943,7 +943,7 @@ int __devm_irq_alloc_descs(struct device *dev, int irq, unsigned int from,
__devm_irq_alloc_descs(dev, irq, from, cnt, node, THIS_MODULE, NULL)

#define devm_irq_alloc_desc(dev, node) \
- devm_irq_alloc_descs(dev, -1, 0, 1, node)
+ devm_irq_alloc_descs(dev, -1, 1, 1, node)

#define devm_irq_alloc_desc_at(dev, at, node) \
devm_irq_alloc_descs(dev, at, at, 1, node)
--
2.29.2
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