Re: [PATCH v6 0/4] Runtime Interpreted Power Sequences

On 09/14/2012 12:24 AM, Stephen Warren wrote:

On 09/13/2012 01:29 AM, Mark Brown wrote:

quoted

On Thu, Sep 13, 2012 at 04:26:34PM +0900, Alex Courbot wrote:

quoted

On Thursday 13 September 2012 15:19:30 Mark Brown wrote:

quoted

quoted

On Thursday 13 September 2012 14:25:53 Mark Brown wrote:

quoted

It would be sensible to make sure that the framework is done in such a
way that drivers can use it - there will be drivers (perhaps not display
ones) that have a known power sequence and which could benefit from the
ability to use library code to implement it based on the user simply
supplying named resources.

quoted

quoted

quoted

Not sure I understand what you mean, but things should be working this way
already - regulators and PWMs are acquired by name using the standard
regulator_get() and pwm_get() functions. GPIOs do not, AFAIK, have a way
to be referenced by name so their number is used instead.

quoted

quoted

Right, but the sequencing for enabling them is currently open coded in
each driver.

quoted

Mmm then I'm afraid I don't see what you wanted to say initially - could you
elaborate?

The driver knows the power sequence.  Having to type the same sequence
into the DT or platform data for each board using the device wouuld be
retarded so we need the drivers to be able to give the sequence to the
library if they're going to be able to reuse it (which is a lot of what
Tomi is talking about).

I believe that's trivial to implement. The relevant function is:

struct power_seq_set *devm_power_seq_set_build(struct device *dev,
		   struct platform_power_seq_set *pseq);

It's up to the driver whether pseq comes from platform data or is
hard-coded into the driver (or not provided at all, for the DT case).
So, the only change needed to convert a "hard-coded" driver to this API
is to convert the current custom data structure (or code) that describes
the sequence into a struct platform_power_seq_set.

If we go this way (which looks good IMO!), then maybe we should abandon 
that "platform" denomination and merge platform_power_seq* structures 
with the currently private power_seq*, and also replace the "building" 
step with a resources acquisition one. Calling these structures 
"platform" implies they are for platform data while they can be used to 
perform more flexible things as Mark mentioned. Also making the resolved 
resource visible would allow drivers to "patch" generic sequences with 
the proper GPIO numbers at runtime. We would also avoid a few memory 
copies and both design and usage would be simplified, at the cost of 
having more things exposed. How does that sound?

Alex.