[PATCH RFC] spi: core: report OF style modalias when probing using DT

[Javier Martinez Canillas]

An SPI driver that supports both OF and legacy platforms, will have
both an OF and SPI ID table. This means that when built as a module,
the aliases will be filled from both tables, e.g:

$ modinfo cros_ec_spi | grep alias
alias:          spi:cros-ec-spi
alias:          of:N*T*Cgoogle,cros-ec-spi*

But currently always an alias of the form spi:<dev_id> is reported
even when the it was probed by matching the OF compatible string.

$ cat /sys/devices/12d40000.spi/spi_master/spi2/spi2.0/modalias
spi:cros-ec-spi

Drivers for IP blocks that are included in DT-only platforms, may not
have an updated SPI ID table so if a device is probed by matching its
compatible string, udev can get a MODALIAS uevent env var that doesn't
match with one of the valid aliases so the module won't be auto-loaded
by libkmod/modprobe.

This patch reports OF related uevent env vars (e.g: OF_COMPATIBLE) and
so the module can be auto-loaded and also report the correctly on sysfs:

$ cat /sys/devices/12d40000.spi/spi_master/spi2/spi2.0/modalias
of:Ncros-ecT<NULL>Cgoogle,cros-ec-spi

Signed-off-by: Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx>
---

NOTE: this will break module auto-loading for all drivers that rely on the
current behavior so it should not be applied unless is part of a series that
fix all the broken drivers.

 drivers/spi/spi.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 95cfe3b..154e1d6 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -63,6 +63,10 @@ modalias_show(struct device *dev, struct device_attribute
*a, char *buf)
 	const struct spi_device	*spi = to_spi_device(dev);
 	int len;

+	len = of_device_get_modalias(dev, buf, PAGE_SIZE - 1);
+	if (len != -ENODEV)
+		return len;
+
 	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
 	if (len != -ENODEV)
 		return len;
@@ -124,6 +128,10 @@ static int spi_uevent(struct device *dev, struct
kobj_uevent_env *env)
 	const struct spi_device		*spi = to_spi_device(dev);
 	int rc;

+	rc = of_device_uevent_modalias(dev, env);
+	if (rc != -ENODEV)
+		return rc;
+
 	rc = acpi_device_uevent_modalias(dev, env);
 	if (rc != -ENODEV)
 		return rc;
-- 
2.1.0
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