Am Samstag, den 19.12.2015, 11:55 +0100 schrieb Hans de Goede: > On 18-12-15 12:08, Maxime Ripard wrote: [...] > > I guess we could also have something like this: > > > > * The driver gets the reference to the reset line using > > reset_control_get or its shared variant. > > > > - If you call reset_control_get on a free line, it succeeds, and > > marks the line in exclusive use. > > - If you call reset_control_get on a busy line, it fails with > > EBUSY > > > > - If you call the shared variant on a free line, it succeeds > > - If you call the shared variant on a busy exclusive line, it > > fails with EBUSY > > - If you call the shared variant on a busy !exclusive line, it > > succeeds. >> > > * The customer driver can then call reset_control_assert / deassert: > > > > - If the reset line is in exclusive use, the assertion happens > > right away, it succeeds and returns 0. > > > > - If the reset line is in a !exclusive use, but with a single > > user, the assertion happens right away, it succeeds and returns > > 0. > > Ack for all of the above, this is what I had in mind at first, but I started > with a more lightweight version as I'm lazy :) If Philipp likes this > suggestion I can rework my patch-set into this. Seconded, this all sounds good to me. > > - If the reset line is in a !exclusive use with more than 1 user, > > the refcount is modified and an error is returned to notify that > > it didn't happen. > > Also ack, except for returning the error, if a driver has used > reset_control_get_shared, it should simply be aware that doing an assert > might not necessarily actually assert the line, just like doing a clk-disable > does not really necessary disable the clock, etc. If a driver is not prepared > to deal with this, it should simply not use reset_control_get_shared. > > I see returning an error if the assert did not happen due to other users / > deassert_count != 0 as inconsistent compared to how clks, regulators and phys > handle this, these all simply return success in this case. I wouldn't want drivers to have to differentiate between relevant and irrelevant error codes, so in the clock-like refcounting use case reset_assert should not return an error if it just correctly decremented the refcount. I'd still prefer to have separate API for the counted must_deassert/may_assert vs the exclusive must_assert/must_deassert use cases, but I just can't think of a good name. regards Philipp -- 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
