[PATCH net-next 2/4] can: at91_can: don't discard the IRQ lookup error in probe

[Chaosheng Qu]

at91_can_probe() looks up the memory resource and the interrupt together
and collapses both failures into -ENODEV:

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	irq = platform_get_irq(pdev, 0);
	if (!res || irq <= 0) {
		err = -ENODEV;
		goto exit_put;
	}

The driver matches through an of_match_table, so of_irq_get() returns
-EPROBE_DEFER while the interrupt controller has not been probed. The
probe overwrites it and the driver core stops retrying, leaving the
device unbound even though the interrupt controller appears later.

The irq <= 0 test also covers a 0 return, which platform_get_irq() never
produces; it warns and returns -EINVAL instead.

Split the two lookups: the memory resource keeps -ENODEV, the interrupt
returns the lookup error unchanged, as the neighbouring CAN platform
drivers do, e.g. commit 057bd6168d98 ("can: cc770: don't discard the IRQ
lookup error in probe"). This also drops an IRQ lookup that cannot
succeed when the memory resource is missing.

A device tree without an interrupt now reports -ENXIO rather than
-ENODEV; the driver core treats both as a failed probe.

Build tested on x86_64.

Assisted-by: LLM
Signed-off-by: Chaosheng Qu <chaosheng.qu.linux@xxxxxxxxx>
---
 drivers/net/can/at91_can.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c
index 58da323f14d7..3977de761636 100644
--- a/drivers/net/can/at91_can.c
+++ b/drivers/net/can/at91_can.c
@@ -1069,12 +1069,17 @@ static int at91_can_probe(struct platform_device *pdev)
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	irq = platform_get_irq(pdev, 0);
-	if (!res || irq <= 0) {
+	if (!res) {
 		err = -ENODEV;
 		goto exit_put;
 	}
 
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		err = irq;
+		goto exit_put;
+	}
+
 	if (!request_mem_region(res->start,
 				resource_size(res),
 				pdev->name)) {
-- 
2.43.0