David Brownell wrote: > On Friday 29 February 2008, Ned Forrester wrote: >> David Brownell wrote: > >>> The chipselect number is always useful when the SPI bus has more >>> than one slave; it's how the slaves are distinguished. >> Ahh... Here is a place where pxa2xx-spi departs from the SPI framework >> by choice. That driver never uses spi_device.chip_select > > Not directly. Indirectly, since each chip_select is associated > with a unique pxa2xx_spi_chip.cs_control(). The chipselect number > (and signal) still distinguishes chips from each other.
Maybe we're just discussing semantics, but the last sentence does not apply to this driver. pxa2xx_spi.c never references the field spi_device.chip_select. The string "chip_select" appears nowhere in the code. You can assign spi_device.chip_select=0 for all chips, and as long as you supply a unique spi_device->controller_data->pxa2xx_spi_chip.cs_control for each chip, chip select will work as intended. So in the sense that I mean, spi_device.chip_select field is unused; it does not need to be unique between chips. Yes, of course there have to be unique spi_device structures for each chip, and through a driver private means (spi_device.controller_data) the chip select mechanism for each chip becomes known to the driver. It was this lack of example for any use of spi_device.chip_select in pxa2xx_spi.c that led to my confusion about how spi_device.chip_select was supposed to be used. -- Ned Forrester [EMAIL PROTECTED] Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
