[RFC 1/4] i2c: core: Allow i2c_board_info to specify that the core should not try to find an IRQ

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

When I2C devices are enumerated/instantiated through ACPI tables then
a single ACPI device may describe multiple separate I2C connected ICs.

This is handled by the drivers/platform/x86/i2c-multi-instantiate.c
code which contains a table which maps the ACPI-device-id to the
information necessary to instantiate the i2c-clients (type and IRQ
routing for each described IC).

In some cases the i2c-driver may need access to the ACPI-fwnode as
that may contain ACPI-methods supplying e.g. orientation-matrix info
for accelerometers.

Currently setting i2c_board_info.fwnode to point to the ACPI-fwnode
will cause the i2c-core to call i2c_acpi_get_irq() for any i2c-clients
for which i2c-multi-instantiate.c has not passed an IRQ in
i2c_board_info.irq, messing up the IRQ routing done by
i2c-multi-instantiate.c.

Make i2c_device_probe() accept a client->init_irq value < 0 to skip
the i2c-core IRQ handling, while still setting client->irq to 0
after checking for this, since most i2c-drivers expect client->irq == 0
for clients without an IRQ.

This allows i2c-multi-instantiate.c to set i2c_board_info.irq = -ENOENT
for clients without an IRQ and pass the ACPI-fwnode without issues.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/i2c/i2c-core-base.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 573b5da145d1..1887e2267031 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -467,11 +467,10 @@ static int i2c_device_probe(struct device *dev)
 			goto put_sync_adapter;
 		}
 
-		if (irq < 0)
-			irq = 0;
-
 		client->irq = irq;
 	}
+	if (client->irq < 0)
+		client->irq = 0;
 
 	driver = to_i2c_driver(dev->driver);
 
-- 
2.28.0