[PATCH] genirq: Fix [devm_]irq_alloc_desc returning irq 0

[Hans de Goede <hdegoede@redhat.com>]

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 c54365309e97..a36d35c25996 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -922,7 +922,7 @@ 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)
@@ -937,7 +937,7 @@ 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)
-- 
2.28.0