[PATCH 3.0-rc2] OMAP: ams-delta: fix broken uevent sysfs entries

Janusz Krzysztofik jkrzyszt at tis.icnet.pl
Wed Jun 15 08:53:01 EDT 2011

On Tue 14 Jun 2011 at 14:00:00 Felipe Balbi wrote:
> On Tue, Jun 14, 2011 at 04:48:48AM -0700, Tony Lindgren wrote:
> > * Janusz Krzysztofik <jkrzyszt at tis.icnet.pl> [110606 18:15]:
> > > Removing __initdata tags, introduced by commit
> > > bdc58fb950a3a1b0bc3cbd8e23d21ecdde2ac9a2, "arm: omap1: fix a
> > > bunch of section mismatches", from corresponding platform_device
> > > structures declared in arch/arm/mach-omap1/board-ams-delta.c,
> > > corrects the problem for me, which may indicate that their
> > > members (.name ?) are still referred to during runtime so they
> > > shouldn't be freed after boot.
> > 
> > Sounds like this needs a bit more research where this initdata
> > gets used?

Not that I didn't do any research before, now I think that not only 
platform_device.name is required. See below.

> to me it sounds like missing __init/__exit annotations on the driver.
> See ams-delta-leds for instance:
> static int ams_delta_led_probe(struct platform_device *pdev)
> static int ams_delta_led_remove(struct platform_device *pdev)
> which means those drivers will have probe sitting outside or
> .init.text and trying to reference name which sits in .init.text ???
> Could that be the case here ?

Missing or not, addig them didn't help.

> But it could also be that the platform_device shouldn't be marked
> __initdata.

After either reverting one of commits mentioned, or applying my patch, 
a read from /sys/devices/platform/ams-delta-led/uevent, for example, 


The code responsible for returning these strings can be found in 

static int dev_uevent(struct kset *kset, struct kobject *kobj,
		struct kobj_uevent_env *env)
	struct device *dev = to_dev(kobj);
	if (dev->driver)
		add_uevent_var(env, "DRIVER=%s", dev->driver->name);

	/* have the bus specific function add its stuff */
	if (dev->bus && dev->bus->uevent) {
                retval = dev->bus->uevent(dev, env);

The dev->bus->uevent for a platform device happens to sit in 

static int platform_uevent(struct device *dev, struct kobj_uevent_env *env)
	struct platform_device  *pdev = to_platform_device(dev);
	add_uevent_var(env, "MODALIAS=%s%s", PLATFORM_MODULE_PREFIX,
		(pdev->id_entry) ? pdev->id_entry->name : pdev->name);

For me, it looks like struct kobject, pointed to by kobj, being a member 
of struct device, which in turn happens to be a member of struct 

AFAICU, there exist two sorts of platform devices from memory allocation 
point of view: those created with platform_device_alloc(), which 
allocates a memory where struct platform_device is kept, and those 
created with platfrom_device_add(), which is provided with a pointer to 
an already allocated platform device structure.

I can't find any piece of code which makes a copy of a platfrom deivce 
structure content pointed to while platform_device_add() is called from 
a board or machine file, either directly or indirectly via 
platform_device_register() or platform_add_devices().
Why should it be actually copied after all?.

Searching for an example usage of _initdata similiar to that introduced 
by commit bdc58fb950a3a1b0bc3cbd8e23d21ecdde2ac9a2, "arm: omap1: fix a 
bunch of section mismatches", I can find the following:

$ grep -r "struct .* platform_device .* = {" .|grep "__initdata"|grep -v '*'
./arch/arm/mach-omap1/board-ams-delta.c:static struct platform_device ams_delta_kp_device __initdata = {
./arch/arm/mach-omap1/board-ams-delta.c:static struct platform_device ams_delta_lcd_device __initdata = {
./arch/arm/mach-omap1/board-ams-delta.c:static struct platform_device ams_delta_led_device __initdata = {
./arch/arm/mach-omap1/board-ams-delta.c:static struct platform_device ams_delta_camera_device __initdata = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_mpu_gpio = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio1 = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio2 = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio3 = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio4 = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio5 = {
./arch/arm/mach-omap1/gpio7xx.c:static struct __initdata platform_device omap7xx_gpio6 = {
./arch/arm/mach-omap1/gpio15xx.c:static struct __initdata platform_device omap15xx_mpu_gpio = {
./arch/arm/mach-omap1/gpio15xx.c:static struct __initdata platform_device omap15xx_gpio = {
./arch/arm/mach-omap1/gpio16xx.c:static struct __initdata platform_device omap16xx_mpu_gpio = {
./arch/arm/mach-omap1/gpio16xx.c:static struct __initdata platform_device omap16xx_gpio1 = {
./arch/arm/mach-omap1/gpio16xx.c:static struct __initdata platform_device omap16xx_gpio2 = {
./arch/arm/mach-omap1/gpio16xx.c:static struct __initdata platform_device omap16xx_gpio3 = {
./arch/arm/mach-omap1/gpio16xx.c:static struct __initdata platform_device omap16xx_gpio4 = {
./arch/arm/mach-omap2/board-rx51-peripherals.c:static struct platform_device rx51_si4713_dev __initdata_or_module = {

So, there is no single exact pattern found in the whole tree, and a few 
instances of similiar patterns of two kinds found only inside omap. If I 
follow any of the two, either moving '__initdata' in front of 
'platform_device' or using '__initdata_or_module' instead, the problem 
no longer hits me (using my custom defconfig). However, the former seems 
not conformant to what one can learn from include/linux/init.h, so I 
suspect that placing __initdata like this can be a noop, while the 
latter means "can be init if no module support", which would probably 
still exhibit the problem if so configured.

How would you like to have this corrected then?


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