On 11/28/2012 01:47 PM, Andy Green wrote:
> On 11/28/2012 07:13 PM, the mail apparently from Roger Quadros included:
>> On 11/27/2012 09:22 PM, Andy Green wrote:
>>> On 11/28/2012 02:09 AM, the mail apparently from Alan Stern included:
>>>> On Wed, 28 Nov 2012, Andy Green wrote:
>>>>
>>>>>> Greg's advice was simply not to rely on pathnames in sysfs because
>>>>>> they
>>>>>> aren't fixed in stone. That leaves plenty of other ways to approach
>>>>>> this problem.
>>>>>
>>>>> It's sage advice, but there is zero code provided in my patches that
>>>>> "relies on pathnames in sysfs".
>>>>
>>>> In your 1/5 patch, _device_path_generate() concatenates device name
>>>> strings, starting from a device root and separating elements with '/'
>>>> characters. Isn't that the same as a sysfs pathname?
>>>
>>> It's nothing to do with sysfs... yes some unrelated bits of sysfs also
>>> walk the device path. If we want to talk about how fragile the device
>>> path is as an id scheme over time we need to talk about likelihood of
>>> individual device names changing, not "sysfs". Anyway -->
>>>
>>>>>> Basically, what you want is for something related to device A (the
>>>>>> regulator or the GPIO) to happen whenever device B (the ehci-omap.0
>>>>>> platform device) is bound to a driver. The most straightforward
>>>>>> way to
>>>>>> arrange this is for A's driver to have a callback that is invoked
>>>>>> whenever B is bound or unbound. The most straightforward way to
>>>>>> arrange _that_ is to allow each platform_device to have a list of
>>>>>> callbacks.
>>>>>
>>>>> Sorry I didn't really understand this proposal yet. You want "A", the
>>>>> regulator, driver to grow a callback function that gets called when
>>>>> the
>>>>> targeted platform_device ("B", ehci-omap.0) probe happens. Could you
>>>>> expand what the callback prototype or new members in the struct might
>>>>> look like? It's your tuple thing or we pass it an opaque pointer that
>>>>> is the struct regulator * or suchlike?
>>>>
>>>> Well, it won't be exactly the same as the tuple thing because no
>>>> strings will be involved, but it would be similar. The callback would
>>>> receive an opaque pointer (presumably to the regulator) and a device
>>>> pointer (the B device).
>>>
>>> OK. So I try to sketch it out iteractively to try to get in sync:
>>>
>>> device.h:
>>>
>>> enum asset_event {
>>> AE_PROBED,
>>> AE_REMOVED
>>> };
>>>
>>> struct device_asset {
>>> char *name; /* name of regulator, clock, etc */
>>> void *asset; /* regulator, clock, etc */
>>> int (*handler)(struct device *dev_owner, enum asset_event
>>> asset_event, struct device_asset *asset);
>>> };
>>>
>>> struct device {
>>> ...
>>> struct device_asset *assets;
>>> ...
>>> };
>>>
>>>
>>> drivers/base/dd.c | really_probe():
>>>
>>> ...
>>> struct device_asset *asset;
>>> ...
>>> asset = dev->assets;
>>> while (asset && asset->name) {
>>> if (asset->handler(dev, AE_PROBED, asset)) {
>>> /* clean up and bail */
>>> }
>>> asset++;
>>> }
>>>
>>> /* do probe */
>>> ...
>>>
>>>
>>> drivers/base/dd.c | __device_release_driver: (is this really the best
>>> place to oppose probe()?)
>>>
>>> ...
>>> struct device_asset *asset;
>>> ...
>>>
>>> /* call device ->remove() */
>>> ...
>>> asset = dev->assets;
>>> while (asset && asset->name) {
>>> asset->handler(dev, AE_REMOVED, asset);
>>> asset++;
>>> }
>>> ...
>>>
>>>
>>> board file:
>>>
>>> static struct regulator myreg = {
>>> .name = "mydevice-regulator",
>>> };
>>>
>>> static struct device_asset mydevice_assets[] = {
>>> {
>>> .name = "mydevice-regulator",
>>> .handler = regulator_default_asset_handler,
>>> },
>>> { }
>>> };
>>>
>>> static struct platform_device mydevice = {
>>> ...
>>> .dev = {
>>> .assets = mydevice_assets,
>>> },
>>> ...
>>> };
>>>
>>
>> From Pandaboard's point of view, is mydevice supposed to be referring to
>> ehci-omap, LAN95xx or something else?
>>
>> Strictly speaking, the regulator doesn't belongs neither to ehci-omap
>> nor LAN95xx. It belongs to a power domain on the board. And user should
>> have control to switch it OFF when required without hampering operation
>> of ehci-omap, so that the other USB ports are still usable.
>
> I'd prefer to deal with that after a try#1 with regulator, I didn't see
> any code about power domain in there right now. There's a lot to get
> consensus on already with this series.
Sure. I meant power domain in the general sense and not referring to any
code or framework in the kernel. It could as well be implemented using
the existing regulator framework.
>
> Notice that these assets are generic, I will provide clk and regulator
> handlers with try#1, and working examples for Panda case with both, but
> presumably power domain can fold into it as well.
>
> Since I am on usb-next and there's nothing to be seen about power
> domains, what is the situation with that support?
>
Looking around there seems to be some power domain framework tied to
runtime PM in drivers/base/power/domain.c
The idea is that the power domain is powered on/off by the runtime PM
core when the device is runtime resumed/suspended. I think this is meant
for SoC power domains and appears to be too complicated for a GPIO based
regulator control.
--
regards,
-roger
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