On 08/26/2013 06:50 PM, wangyuhang wrote: > Add spi-tmax-nbits and spi-rmax-nbits for spi slave node. > Modify the related dt document(spi-bus.txt) > spi-tmax-nbits:Max number of bits slave will use for MOSI(writting) > spi-rmax-nbits:Max number of bits slave will use for MISO(reading) > Support for spi-tx/rmax-nbits in SPI framework has been picked[1]. > [1]: http://comments.gmane.org/gmane.linux.kernel.spi.devel/14420 > Commit Id:f477b7fb13df2b843997559ff34e87d054ba6538 > diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt > +- spi-tmax-nbits - (optional) Max number of bits slave will use for > + MOSI(writting) > +- spi-rmax-nbits - (optional) Max number of bits slave will use for > + MISO(reading) I would suggest the property names spi-tx-num-wires, spi-rx-num-wires or: spi-tx-bus-width, spi-rx-bus-width (this option from Tomasz Figa on IRC) Those name alone self-document their purpose much more clearly to me. I would also change the descriptions a bit, resulting in the following overall: ========== - spi-tx-num-wires - (optional) The number of data wires that transfer data from the SPI controller to the SPI device. Defaults to 1 if not present. - spi-rx-num-wires - (optional) The number of data wires that transfer data from the SPI device to the SPI controller. Defaults to 1 if not present. ========== > +So if for example the slave has 4 wires for writting and 2 wires for reading, > +and the spi-tx/rx-nbits property should be set as follows: > + > +spi-tmax-nbits = <4>; > +spi-rmax-nbits = <2>; > + > +Now the value that spi-tmax-nbits and spi-rmax-nbits can receive is only > +1(single), 2(dual) and 4(quad). If you don't set spi-tmax-nbits or spi-rmax-nbits, > +spi_device mode will be set in single(1 wire) as default. Another point, if > +property:spi-3wire is set, spi-t/rmax-nbits is forbidden to set to <2 or 4>, > +otherwise, an errro will return. I think most of that explanation can be removed if you use the text I wrote above. I'm not sure you should ban spi-3wire if those properties are specified; can't all those properties be present together, if the num-wires are set to 1? Actually, isn't spi-3write the default; what does that property mean? -- 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
