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 -4 for this (I left -2 and -3 free in case we ever need a couple of other magic values.) The automatically allocated device IDs are global (to avoid an additional per-driver cost) and are stored internally as negative numbers, starting with -4. This is required so that the IDs can be freed later. Externally the positive value is used. Signed-off-by: Jean Delvare <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> --- If anyone has a problem with the -4 or using negative device IDs internally, it would be possible to avoid that by adding a boolean attribute to every platform device to record whether the ID needs to be freed. This would cost some memory. drivers/base/platform.c | 33 +++++++++++++++++++++++++++++++-- include/linux/platform_device.h | 3 +++ 2 files changed, 34 insertions(+), 2 deletions(-) --- linux-3.5.orig/drivers/base/platform.c 2012-07-26 08:36:58.817173740 +0200 +++ linux-3.5/drivers/base/platform.c 2012-07-27 12:43:19.167592926 +0200 @@ -20,9 +20,13 @@ #include <linux/err.h> #include <linux/slab.h> #include <linux/pm_runtime.h> +#include <linux/idr.h> #include "base.h" +/* For automatically allocated device IDs */ +static DEFINE_IDA(platform_devid_ida); + #define to_platform_driver(drv) (container_of((drv), struct platform_driver, \ driver)) @@ -273,10 +277,29 @@ int platform_device_add(struct platform_ pdev->dev.bus = &platform_bus_type; - if (pdev->id != -1) + switch (pdev->id) { + default: dev_set_name(&pdev->dev, "%s.%d", pdev->name, pdev->id); - else + break; + case PLATFORM_DEVID_NONE: dev_set_name(&pdev->dev, "%s", pdev->name); + break; + case PLATFORM_DEVID_AUTO: + /* + * Automatically allocated device ID. Stored as a negative + * number so that we remember it must be freed. We use the + * opposite in the device name so that the user still sees a + * positive device ID. And we append a suffix to avoid + * namespace collision with explicit IDs. + */ + i = ida_simple_get(&platform_devid_ida, -PLATFORM_DEVID_AUTO, 0, + GFP_KERNEL); + if (i < 0) + return i; + pdev->id = -i; + dev_set_name(&pdev->dev, "%s.%d.auto", pdev->name, -pdev->id); + break; + } for (i = 0; i < pdev->num_resources; i++) { struct resource *p, *r = &pdev->resource[i]; @@ -309,6 +332,9 @@ int platform_device_add(struct platform_ return ret; failed: + if (pdev->id <= PLATFORM_DEVID_AUTO) + ida_simple_remove(&platform_devid_ida, -pdev->id); + while (--i >= 0) { struct resource *r = &pdev->resource[i]; unsigned long type = resource_type(r); @@ -336,6 +362,9 @@ void platform_device_del(struct platform if (pdev) { device_del(&pdev->dev); + if (pdev->id <= PLATFORM_DEVID_AUTO) + ida_simple_remove(&platform_devid_ida, -pdev->id); + for (i = 0; i < pdev->num_resources; i++) { struct resource *r = &pdev->resource[i]; unsigned long type = resource_type(r); --- linux-3.5.orig/include/linux/platform_device.h 2012-07-21 22:58:29.000000000 +0200 +++ linux-3.5/include/linux/platform_device.h 2012-07-27 10:57:20.378726053 +0200 @@ -14,6 +14,9 @@ #include <linux/device.h> #include <linux/mod_devicetable.h> +#define PLATFORM_DEVID_NONE (-1) +#define PLATFORM_DEVID_AUTO (-4) + struct mfd_cell; struct platform_device { -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
