[PATCH 1/1] mmc: add MODALIAS linkage for MMC/SD devices

[Andy Whitcroft <apw@canonical.com>]

[Here is an updated patch which only uses information already exported in
the ABI.]

Currently we are using an explicit udev rule to trigger loading of the
mmc-block module when an MMC or SD card is detected:

    SUBSYSTEM=="mmc", RUN+="/sbin/modprobe -Qba mmc-block"

It makes much more sense for the mmc bus driver and the mmc-block module to
share MODALIAS information so that they are linked automatically.

Add MODALIAS attributes to the uevents as generated, and add the
corresponding MODULE_ALIAS marks to the mmc-block module so that it is
automatically loaded by udev.  Following discussion it was decided to
expose the textual types, and so I have followed the example set by
the dmi: aliases for handling text.  The aliases are of the following
form:

    mmc:t<type>:

For example:

    mmc:tMMC:

The entry ends with a separator (:) in order to allow simple differentiation
between common prefixes such as SD and SDIO in MODULE_ALIAS declarations.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
 drivers/mmc/card/block.c |    3 +++
 drivers/mmc/core/bus.c   |    5 +++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 3d067c3..9799273 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -41,6 +41,9 @@
 
 #include "queue.h"
 
+MODULE_ALIAS("mmc:tMMC:*");
+MODULE_ALIAS("mmc:tSD:*");
+
 /*
  * max 8 partitions per card
  */
diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
index f210a8e..7b34c00 100644
--- a/drivers/mmc/core/bus.c
+++ b/drivers/mmc/core/bus.c
@@ -84,6 +84,11 @@ mmc_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
 	}
 
 	retval = add_uevent_var(env, "MMC_NAME=%s", mmc_card_name(card));
+	if (retval)
+		return retval;
+
+	retval = add_uevent_var(env, "MODALIAS=mmc:t%s:",
+						(type) ? type : "UNKNOWN");
 
 	return retval;
 }
-- 
1.6.1.258.g7ff14.dirty