On Wed, Feb 01, 2017 at 12:10:17AM +0100, Rafael J. Wysocki wrote: > On Tue, Jan 3, 2017 at 7:33 AM, Peter Chen <peter.chen@xxxxxxx> wrote: > > We have an well-known problem that the device needs to do some power > > sequence before it can be recognized by related host, the typical > > example like hard-wired mmc devices and usb devices. > > > > This power sequence is hard to be described at device tree and handled by > > related host driver, so we have created a common power sequence > > library to cover this requirement. The core code has supplied > > some common helpers for host driver, and individual power sequence > > libraries handle kinds of power sequence for devices. The pwrseq > > librares always need to allocate extra instance for compatible > > string match. > > > > pwrseq_generic is intended for general purpose of power sequence, which > > handles gpios and clocks currently, and can cover other controls in > > future. The host driver just needs to call of_pwrseq_on/of_pwrseq_off > > if only one power sequence is needed, else call of_pwrseq_on_list > > /of_pwrseq_off_list instead (eg, USB hub driver). > > > > For new power sequence library, it can add its compatible string > > to pwrseq_of_match_table, then the pwrseq core will match it with > > DT's, and choose this library at runtime. > > > > Signed-off-by: Peter Chen <peter.chen@xxxxxxx> > > Tested-by: Maciej S. Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx> > > Tested-by Joshua Clayton <stillcompiling@xxxxxxxxx> > > Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> > > Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> > > Quite honestly, I have a really hard time with trying to follow this > code and the total lack of documentation makes it even harder. In > particular, the generic power sequence code is not even commented at > all, so it really is hard to say how this is going to work, let alone > deciding whether or not to apply it. > > Plus, of course, the USB core changes must be acked by the maintainer > thereof for me to be able to handle the series. Ah crap, I wanted you to explain it as I too couldn't figure it out :) > But at this point I basically need you to explain the design to me, please. Same here. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
