On Tuesday 30 October 2007, Bryan Wu wrote: > Maybe there are some confusion of mixing up the spi_trasnfer.speed_hz > with the spi_device.max_speed_hz. > > spi_device.max_speed_hz comes from spi_board_info.max_speed_hz, it is > for the default max speed value.
It's initialized from board_info, yes. Drivers can override it using spi_setup(). One would expect they only override _downwards_ but that's not guaranteed anywhere. A driver might have a way to establish that this particular board can run faster, for example. > spi_transfer.speed_hz comes from upper applications for each spi > transfer setting. Certainly; all spi_transfer records come from applications! If that value is zero, that transfer segment uses the limit from the spi_device ... otherwise, it can differ. Again, the limits can vary based on devise characteristics; maybe it can't feed data as fast for some commands. (ISTR the M25P16 in $SUBJECT has two read commands, one of which is only usable at clock rates below 33 MHz or so, but most other commands can work above that speed just fine.) - Dave - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
