`pci230_ai_read()` reads a sample from the ADC data register and converts it to a comedi sample value. The AI sample may have 12 or 16 bits of resolution, depending on the board type, but 12-bit sample values are in bits 15 to 4 of the register. The hardware value is signed, 2's complement if set to a bipolar mode, or unsigned, straight binary if set to a unipolar mode. To convert to a Comedi sample value it may need shifting right by 4 bits, and the top bit of the sample value may need to be toggled. Simplify the existing code by doing the 2's complement to straight binary conversion before the shift. That way, it is always bit 15 that is inverted regardless of the resolution. Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx> --- drivers/staging/comedi/drivers/amplc_pci230.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/drivers/staging/comedi/drivers/amplc_pci230.c b/drivers/staging/comedi/drivers/amplc_pci230.c index e4151d7..70b210b 100644 --- a/drivers/staging/comedi/drivers/amplc_pci230.c +++ b/drivers/staging/comedi/drivers/amplc_pci230.c @@ -563,16 +563,13 @@ static unsigned short pci230_ai_read(struct comedi_device *dev) /* * PCI230 is 12 bit - stored in upper bits of 16 bit register * (lower four bits reserved for expansion). PCI230+ is 16 bit AI. - */ - data = data >> (16 - thisboard->ai_bits); - - /* + * * If a bipolar range was specified, mangle it * (twos complement->straight binary). */ if (devpriv->ai_bipolar) - data ^= 1 << (thisboard->ai_bits - 1); - + data ^= 0x8000; + data >>= (16 - thisboard->ai_bits); return data; } -- 2.0.4 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
