[PATCH 2/3] OMAP2+ devices add mac address allocation register api

[andy.green@linaro.org (Andy Green)]

On 06/29/12 17:40, the mail apparently from Tony Lindgren included:
> * Andy Green <andy.green@linaro.org> [120628 22:59]:
>> From: Andy Green <andy@warmcat.com>
>>
>> This exposes a new API in devices.c that lets a board register
>> a list of device paths representing network devices that have
>> no arrangements for their MAC address to be set by the board.
>>
>> It watches network device registrations via a notifier and
>> gives the devices requiring them a synthetic - but constant for
>> a given board - MAC address immediately.
> ...
>
>> --- a/arch/arm/mach-omap2/devices.c
>> +++ b/arch/arm/mach-omap2/devices.c
>> @@ -39,6 +42,9 @@
>>   #define L3_MODULES_MAX_LEN 12
>>   #define L3_MODULES 3
>>
>> +static const char * const *mac_device_fixup_paths;
>> +int count_mac_device_fixup_paths;
>
> This too should be static it seems to me. Or just make the
> paths array NULL terminated to get rid of the count.
>
>>   static int __init omap3_l3_init(void)
>>   {
>>   	struct omap_hwmod *oh;
>> @@ -627,6 +633,89 @@ static void omap_init_vout(void)
>>   static inline void omap_init_vout(void) {}
>>   #endif
>>
>> +static int omap_device_path_need_mac(struct device *dev)
>> +{
>> +	const char **try = (const char **)mac_device_fixup_paths;
>
> This cast you should be able to remove by setting the types right
> to start with?

I guess so, I recall meddling with it and throwing a cast at it.

>> +	const char *path;
>> +	int count = count_mac_device_fixup_paths;
>> +	const char *p;
>> +	int len;
>> +	struct device *devn;
>> +
>> +	while (count--) {
>> +
>> +		p = *try + strlen(*try);
>> +		devn = dev;
>> +
>> +		while (devn) {
>> +
>> +			path = dev_name(devn);
>> +			len = strlen(path);
>> +
>> +			if ((p - *try) < len) {
>> +				devn = NULL;
>> +				continue;
>> +			}
>> +
>> +			p -= len;
>> +
>> +			if (strncmp(path, p, len)) {
>> +				devn = NULL;
>> +				continue;
>> +			}
>> +
>> +			devn = devn->parent;
>> +			if (p == *try)
>> +				return count;
>> +
>> +			if (devn != NULL && (p - *try) < 2)
>> +				devn = NULL;
>> +
>> +			p--;
>> +			if (devn != NULL && *p != '/')
>> +				devn = NULL;
>> +		}
>> +
>> +		try++;
>> +	}
>> +
>> +	return -ENOENT;
>> +}
>
> I don't quite like having this device parsing code here. This should
> probably be a generic helper function somewhere under drivers. I would
> assume other SoCs could use it too?

OK... is it a job for drivers/misc or is there a better idea?

>> +static int omap_panda_netdev_event(struct notifier_block *this,
>> +						unsigned long event, void *ptr)
>> +{
>> +	struct net_device *dev = ptr;
>> +	struct sockaddr sa;
>> +	int n;
>> +
>> +	if (event != NETDEV_REGISTER)
>> +		return NOTIFY_DONE;
>> +
>> +	n = omap_device_path_need_mac(dev->dev.parent);
>> +	if (n < 0)
>> +		return NOTIFY_DONE;
>> +
>> +	sa.sa_family = dev->type;
>> +	omap2_die_id_to_ethernet_mac(sa.sa_data, n);
>> +	dev->netdev_ops->ndo_set_mac_address(dev, &sa);
>> +
>> +	return NOTIFY_DONE;
>> +}
>> +
>> +static struct notifier_block omap_panda_netdev_notifier = {
>> +	.notifier_call = omap_panda_netdev_event,
>> +	.priority = 1,
>> +};
>
> This is a bit similar to platform data callback functions that we are
> trying to get rid of. And as the question "how do we replace platform
> data callback functions" is still open for things like this, few
> questions come to mind that should be discussed:
>
> 1. How is this a better solution to passing the generated mac address in
>     platform data to the driver?

Well, I initially did this over a year ago as a generic way to pass 
platform data to devices that are appearing through deferred or async 
probing, like USB bus and SDIO bus.  It was not understood what the goal 
was by the people looking after those subsystems.

> 2. Is this really how we want to pass the board generated mac addresses
>     and other dynamically generated data to the drivers that are device
>     tree based?

The issue is that both these busses have an async probe, in the case of 
USB stack the maintainer was not interested last year in adding platform 
data.  Maybe it changed but that's my understanding.

> 3. What about mac address in board-generic.c when booting panda with
>     device tree?

I don't mind adapting it for that case.

> Also, what happens if the user has set the mac address and you replugs the
> cable or device? Do we now overwrite it? Might be worth checking that this
> follows the standard behaviour..

This is only useful for devices that are soldered on your board, and 
have deterministic "device paths" as is the case with Panda Ethernet and 
Wlan module that both benefit from this treatment.  If you mean pulling 
the RJ45 cable, it doesn't change anything about the MAC I can confirm.

-Andy

-- 
Andy Green | TI Landing Team Leader
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