On Tue, Sep 05, 2017 at 11:56:02AM +0200, Arnd Bergmann wrote: > On Tue, Sep 5, 2017 at 11:44 AM, Lukas Wunner <lukas@xxxxxxxxx> wrote: > > The Texas Instruments DAC7512 has the exact same pinout, programming > > interface and power-down modes as the Texas Instruments DAC121S101 and > > Analog Devices AD5320, which are already supported by the IIO driver > > ad5446.c. Remove the duplicate misc driver. > > > > This requires user space to migrate to the standardized IIO sysfs ABI. > > (In other words, it needs to change a filename.) > > > > The IIO driver supports the chip's features more fully, e.g. the ability > > to power down the output or choose one of the available powerdown modes. > > > > There is an oddity with the misc driver in that it initializes the SPI > > slave to SPI_MODE_0, in contradiction to the datasheet which specifies > > that data is latched in on the falling edge, implying that SPI_MODE_1 > > or SPI_MODE_2 must be used. Another oddity is that Kconfig and the > > MODULE_DESCRIPTION() claim the chip has 16-bit resolution although it > > actually has 12-bit. > > > > Datasheets: > > http://www.ti.com/lit/ds/symlink/dac7512.pdf > > http://www.ti.com/lit/ds/symlink/dac121s101.pdf > > http://www.analog.com/media/en/technical-documentation/data-sheets/AD5320.pdf > > > > Cc: Daniel Mack <daniel@xxxxxxxxxx> > > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > > Good catch, removing duplicate code is usually a good idea. > > However, for the incompatible user space ABI change, we need a better > reasoning why this is safe to do and won't catch users by surprise. > > If anyone relies on the old ABI and can't be expected to change, > we need to stay compatible. Do we know who uses the old driver? Daniel introduced it for use in Raumfeld speakers. The IIO subsystem predates this driver by a few months. I don't know why it uses a nonstandard file in sysfs and wasn't based on IIO. I'm wondering if the driver has ever worked because of the SPI_MODE_0 issue mentioned above. If it did, it must have been by accident. Or the datasheet is wrong, which seems unlikely. > > - > > -static const struct spi_device_id dac7512_id_table[] = { > > - { "dac7512", 0 }, > > - { } > > -}; > > -MODULE_DEVICE_TABLE(spi, dac7512_id_table); > > - > > -#ifdef CONFIG_OF > > -static const struct of_device_id dac7512_of_match[] = { > > - { .compatible = "ti,dac7512", }, > > - { } > > -}; > > The other driver doesn't appear to have an of_match table, so > I suspect it won't automatically get loaded. I added one in this patch, check again. > Can you update > Documentation/devicetree/bindings/iio/dac/ti,dac7512.txt > in an appropriate way to list all the IDs that are supported > by the IIO driver, and make sure that the driver supports > all the IDs that it needs? There are no DT bindings documented for ad5446.c, so I left this file as is, its contents continue to apply. I guess I could amend the newly introduced OF match table with all existing SPI IDs supported by ad5446.c and document those in the DT bindings if desired? Thanks, Lukas -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
