On Fri, Oct 22, 2010 at 03:25, Grant Likely wrote: > On Fri, Oct 22, 2010 at 02:41:12AM -0400, Mike Frysinger wrote: >> On Fri, Oct 22, 2010 at 02:30, Grant Likely wrote: >> > On Fri, Oct 22, 2010 at 02:01:47AM -0400, Mike Frysinger wrote: >> >> From: Michael Hennerich <michael.henner...@analog.com> >> >> >> >> The gpiolib code does not allow people to do gpio_request() on a GPIO >> >> once it has already been requested. So make sure we only request the >> >> pin on the first setup of a SPI device. Otherwise, if you attempts to >> >> reconfigure a SPI device on the fly (like change bit sizes), the setup >> >> function incorrectly fails. >> > >> > Doesn't that mean that the gpio pin be requested at device probe time >> > instead of in a function that can be repeatedly called? >> >> not sure what you mean. this is a pin specific to a spi slave device. >> there is no "spi probe" function for spi slave devices, only the "spi >> setup" function. > > The spi master device is responsible for managing its own cs lines, > and it should know what they are at bfin_spi_probe time. Looking at > commit d3cc71f7 which reworked the cs_gpio bits, I see that the > blackfin driver places the gpio information with the slave instance. > > One could be argue that the spi_slave can be considered the owner of > spi ss lines, but that runs counter to current conventions, and > counter to how I want to implement common infrastructure for handling > gpio slave select lines. > > I see that this patch is a bug fix, and the driver already implements > bad behaviour, so I have little choice but to pick it up. However, it > is only a band-aid solution and in the long term it should be > refactored to store the gpio slave-select lines with the spi_master > device (probably after some common gpio-slave-select infrastructure is > put in place).
i disagree. if any GPIO at all may be used as a CS, how could the SPI master driver have any idea at all what GPIO a slave might choose to use ? or who is to say that the GPIO in question is available when the SPI bus master registers itself if the GPIO sits on a GPIO expander board (e.g. i2c) and not the SOC ? this is information that only the SPI client knows about and that the slave device is binding to. putting slave information into the master resources makes no sense to me. -mike ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ spi-devel-general mailing list spi-devel-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/spi-devel-general
