From 2f644ccfc5a3195290d12b8eedf18a37bba27d98 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Tue, 18 Jan 2011 17:44:33 +0000 Subject: [PATCH] staging: comedi: Make INSN_BITS behavior consistent across drivers Most comedi hardware drivers that support the INSN_BITS instruction ignore the base channel (specified by insn->chanspec) and assume it is 0. The base channel is supposed to affect how the mask (in data[0]) and bits (in data[1]) are treated. Bit 0 applies to the base channel, bit 1 applies to base channel plus 1, etc. For subdevices with no more than 32 channels, this patch modifies the chanspec and data before presenting it to the hardware driver, and modifies the data bits read back by the hardware driver (into data[1]). This makes it appear to the hardware driver that the base channel was set to 0. For subdevices with more than 32 channels, the instruction is left unmodified, as it is assumed that the hardware driver takes note of the base channel in this case in order to provide access beyond channel 31. Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 093032ba..a4ceb29c 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -910,9 +910,28 @@ static int parse_insn(struct comedi_device *dev, struct comedi_insn *insn, case INSN_BITS: if (insn->n != 2) { ret = -EINVAL; - break; + } else { + /* Most drivers ignore the base channel in + * insn->chanspec. Fix this here if + * the subdevice has <= 32 channels. */ + unsigned int shift; + unsigned int orig_mask; + + orig_mask = data[0]; + if (s->n_chan <= 32) { + shift = CR_CHAN(insn->chanspec); + if (shift > 0) { + insn->chanspec = 0; + data[0] <<= shift; + data[1] <<= shift; + } + } else + shift = 0; + ret = s->insn_bits(dev, s, insn, data); + data[0] = orig_mask; + if (shift > 0) + data[1] >>= shift; } - ret = s->insn_bits(dev, s, insn, data); break; case INSN_CONFIG: ret = check_insn_config_length(insn, data); -- 2.7.4