On Wed, Jun 28, 2017 at 07:33:33PM +0200, Mike Looijmans wrote: > On 28-06-17 19:02, Tom Levens wrote: > > > >On Wed, 28 Jun 2017, Guenter Roeck wrote: > > > >>On Wed, Jun 28, 2017 at 05:29:38PM +0200, Tom Levens wrote: > >>> > >>[ ... ] > >> > >>>> > >>>>>Whatever happened to this patch though? It didn't make it to mainline, > >>>>>otherwise I'd have found it sooner... > >>>>> > >>>>I'll have to look it up, but I guess I didn't get an updated version. > >>> > >>>As far as I remember I had a working V3 of this patch, but it is > >>>entirely > >>>possible that it was never submitted as I have been busy with other > >>>projects > >>>recently. I'll dig it out and check that it is complete. > >>> > >>FWIW, I don't see it at > >>https://patchwork.kernel.org/project/linux-hwmon/list/?submitter=171225&state=* > >> > >> > >>Maybe you were waiting for a reply from Rob. Either case, it might make > >>sense to only provide valid modes, ie to abstract the mode bits from the > >>hardware, such as > >> > >>0 - internal temp only > >>1 - Tr1 > >>2 - V1 > >>3 - V1-V2 > >>4 - Tr2 > >>5 - V3 > >>6 - V3-V4 > >>7 to 14 - per bit 0..2 > >> > >>Guenter > >> > > > >You are right, there was still an open question about how best to handle > >the mode selection in DT. > > > >In the latest version of my patch I have it implemented as an array for > >setting the two values, for example: > > > > lltc,meas-mode = <7 3>; > > > >This sets bits [2..0] = 7 and [4..3] = 3. Of course these could be split > >into two DT properties, but I was unsure what to name them as both fields > >are called "mode" in the datasheet and "mode-43"/"mode-20" (or similar) is > >ugly. > > > >With regards to your proposal, it is not clear to me whether the modes > >which have the same result are exactly equivalent. Does disabling a > >measurement with the mode[4..3] bits really leaves the part in a safe > >state for all possible HW connections? With this doubt in my head, I would > >prefer to keep the option available to the user to select any specific > >mode. But I am open to suggestions. > > Well, the input restrictions always apply, so disabling V3 measurement > doesn't imply that you can apply 20V to that input safely now. > > I'd suggest to set unused input to plain voltage measurement. That is > "passive" and safe for external components. > > So I'd suggest just setting the mode as per device datasheet, I can see no > real advantage in abstracting it away and forcing users to read yet another > document to get it right, e.g.: > > lltc,mode = <6>; > > As for the input disabling, since I doubt anyone would use it (why purchase > a 4-channel device and use only 2), just add two booleans, e.g. > "disable-inputs-34" and "disable-inputs-12" which set the command bits > appropriately, and change the mode such that the disabled inputs are voltage > readout only. > > A case could even be made for changing mode at runtime. This allows using it > to measure both current and voltage on two inputs, by reading V1, and V3, > and then switch mode to obtain (accurate) V1-V2 and V4-V3. > The hwmon subsystem doesn't really currently support that, and you'll likely confuse userspace as well. > That might be a viable way to handle not setting the mode at all. If the > mode can be selected via sysfs, the driver can keep the device in a "safe" > mode until the mode has been selected. > You'll have to present me with a really good use case for me to agree with that approach. Guenter > > >Mike, if you would like to test it, the latest version of my code is here: > > > >https://github.com/levens/ltc2990/blob/dev/drivers/hwmon/ltc2990.c > > Sure, I even have a board with 2 of these devices now :) > > -- > Mike Looijmans > > > Kind regards, > > Mike Looijmans > System Expert > > TOPIC Products > Materiaalweg 4, NL-5681 RJ Best > Postbus 440, NL-5680 AK Best > Telefoon: +31 (0) 499 33 69 79 > E-mail: mike.looijmans@xxxxxxxxxxxxxxxxx > Website: www.topicproducts.com > > Please consider the environment before printing this e-mail > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
