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. > >> >> + 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 devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
