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platform: Add support for automatic device IDs

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Right now we have support for explicit platform device IDs, as well as
ID-less platform devices when a given device type can only have one
instance. However there are cases where multiple instances of a device
type can exist, and their IDs aren't (and can't be) known in advance
and do not matter. In that case we need automatic device IDs to avoid
device name collisions.

I am using magic ID value -2 (PLATFORM_DEVID_AUTO) for this, similar
to -1 for ID-less devices. The automatically allocated device IDs are
global (to avoid an additional per-driver cost.) We keep note that the
ID was automatically allocated so that it can be freed later.

Note that we also restore the ID to PLATFORM_DEVID_AUTO on error and
device deletion, to avoid avoid unexpected behavior on retry. I don't
really expect retries on platform device addition, but better safe
than sorry.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jean Delvare 2012-07-27 22:14:59 +02:00 • committed by Greg Kroah-Hartman
parent a525a3ddea
commit 689ae231af
2 changed files with 39 additions and 3 deletions
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4
include/linux/platform_device.h
View file

@ -14,11 +14,15 @@
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#define PLATFORM_DEVID_NONE (-1)
#define PLATFORM_DEVID_AUTO (-2)
struct mfd_cell;
struct platform_device {
const char * name;
int id;
bool id_auto;
struct device dev;
u32 num_resources;
struct resource * resource;