linux-kernel - [PATCH 1/3] ACPI: add module autoloading support for ACPI enumerated devices

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Date:	Mon, 14 Oct 2013 17:10:32 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	rjw@...k.pl
Cc:	linux-acpi@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, jarkko.nikula@...ux.intel.com,
	mika.westerberg@...ux.intel.com, Zhang Rui <rui.zhang@...el.com>
Subject: [PATCH 1/3] ACPI: add module autoloading support for ACPI enumerated devices

An ACPI enumerated device may have its compatible id strings.

To support the compatible ACPI ids (acpi_device->pnp.ids),
we introduced acpi_driver_match_device() to match
the driver->acpi_match_table and acpi_device->pnp.ids.

For those drivers, MODULE_DEVICE_TABLE(acpi, xxx) is used to
exports the driver module alias in the format of
"acpi:device_compatible_ids".
But in the mean time, the current code does not export the
ACPI compatible strings as part of the module_alias for the
ACPI enumerated devices, which will break the module autoloading.

Take the following piece of code for example,
static const struct acpi_device_id xxx_acpi_match[] = {
        { "INTABCD", 0 },
        { }
};
MODULE_DEVICE_TABLE(acpi, xxx_acpi_match);

If this piece of code is used in a platform driver for
an ACPI enumerated platform device, the platform driver module_alias
is "acpi:INTABCD", but the uevent attribute of its platform device node
is "platform:INTABCD:00" (PREFIX:pdev->name).
If this piece of code is used in an i2c driver for an ACPI enumerated
i2c device, the i2c driver module_alias is "acpi:INTABCD", but
the uevent of its i2c device node is "i2c:INTABCD:00" (PREFIX:client->name).

The reason why the module autoloading is not broken for now is that
the uevent file of the ACPI device node is "acpi:INTABCD".
Thus it is the ACPI device node creation that loads the platform/i2c driver.

So this is a problem that will affect us the day when the ACPI bus
is removed from device model.

This patch introduces a new function to exporting ACPI ids as the
module_alias, for the ACPI enumerate devices.

For any drivers using MODULE_DEVICE_TALBE(acpi, blabla), the uevent file
of its associated device must be fixed by invoking this function.

Signed-off-by: Zhang Rui <rui.zhang@...el.com>
---
 drivers/acpi/scan.c  |   24 ++++++++++++++++++++++++
 include/linux/acpi.h |    8 ++++++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 407ad13..db6f879 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -111,6 +111,30 @@ static int create_modalias(struct acpi_device *acpi_dev, char *modalias,
 	return len;
 }

+int acpi_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct acpi_device *acpi_dev;
+	int result;
+	int len;
+
+	result = acpi_bus_get_device(ACPI_HANDLE(dev), &acpi_dev);
+	if (result)
+		return result;
+
+	if (list_empty(&acpi_dev->pnp.ids))
+		return 0;
+
+	if (add_uevent_var(env, "MODALIAS="))
+		return -ENOMEM;
+	len = create_modalias(acpi_dev, &env->buf[env->buflen - 1],
+				sizeof(env->buf) - env->buflen);
+	if (len >= (sizeof(env->buf) - env->buflen))
+		return -ENOMEM;
+	env->buflen += len;
+	return 0;
+}
+EXPORT_SYMBOL(acpi_device_uevent_modalias);
+
 static ssize_t
 acpi_device_modalias_show(struct device *dev, struct device_attribute *attr, char *buf) {
 	struct acpi_device *acpi_dev = to_acpi_device(dev);
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index a5db4ae..117fa26 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -401,6 +401,8 @@ static inline bool acpi_driver_match_device(struct device *dev,
 	return !!acpi_match_device(drv->acpi_match_table, dev);
 }

+int acpi_device_uevent_modalias(struct device *, struct kobj_uevent_env *);
+
 #define ACPI_PTR(_ptr)	(_ptr)

 #else	/* !CONFIG_ACPI */
@@ -471,6 +473,12 @@ static inline bool acpi_driver_match_device(struct device *dev,
 	return false;
 }

+static inline int acpi_device_uevent_modalias(struct device *dev,
+				struct kobj_uevent_env *env)
+{
+	return -ENODEV;
+}
+
 #define ACPI_PTR(_ptr)	(NULL)

 #endif	/* !CONFIG_ACPI */
-- 
1.7.9.5

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