On Fri, Apr 4, 2014 at 10:14 PM, Harini Katakam <harinikatakamlinux@xxxxxxxxx> wrote: > Hi Mark, > > On Fri, Apr 4, 2014 at 3:39 PM, Mark Brown <broonie@xxxxxxxxxx> wrote: >> On Fri, Apr 04, 2014 at 08:30:38AM +0530, Harini Katakam wrote: >>> On Fri, Apr 4, 2014 at 3:04 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: >>> > On Thu, Apr 03, 2014 at 04:40:31PM +0530, Harini Katakam wrote: >> >>> >> +Optional properties: >>> >> +- num-cs : Number of chip selects used. >> >>> > How does this translate to the hardware? >> >>> This IP can drive 4 slaves. >>> The CS line to be driven is selected in spi device structure and >>> that is driven by the software. >> >> So why specify this in the binding at all? If the device always has the >> same number of chip selects it's redundant. > > I'm sorry, I should have explained that better. > The IP can support upto 4 chip selects. > The num-cs value here is the number of chip selects actually used on the board. > Just to clarify - do you mean SoC or board level? Regards, Peter >> >>> >> + num-cs = /bits/ 16 <4>; >> >>> > What's going on with the /bits/ - is this something that's required for >>> > the property? >> >>> The master->num-chipselect property is 16 bit but writing <4> here directly >>> leads to 0 being read in of_property_read (because it's big endian). >>> Instead using of property read u32 and then copying, we decided to do this. >>> This was discussed on v2 between Michal and Rob: >> >> No, don't do that. You're contorting the binding to serve Linux's >> implementation needs and you've not documented this requirement either. >> If there *was* a need to have the number be 16 bits you'd need to >> document that reqirement in the binding, though like I say I don't think >> the number needs to be there at all. > > OK. I'll remove the /bits/ 16 and handle it in the driver. > > Regards, > Harini > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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
