From: Ian Abbott <abbotti@mev.co.uk>
To: driverdev-devel@linuxdriverproject.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ian Abbott <abbotti@mev.co.uk>,
H Hartley Sweeten <hartleys@visionengravers.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 14/28] staging: comedi: amplc_pci230: simplify pci230_ao_mangle_datum()
Date: Mon, 1 Sep 2014 12:03:46 +0100 [thread overview]
Message-ID: <1409569440-10979-15-git-send-email-abbotti@mev.co.uk> (raw)
In-Reply-To: <1409569440-10979-1-git-send-email-abbotti@mev.co.uk>
`pci230_ao_mangle_datum()` converts comedi sample values for the AO
subdevice to hardware register values. The comedi sample value will be
an unsigned value in the range 0 to 4095 (assuming 12-bit resolution).
The hardware wants the value shifted so the m.s. bit of the sample in in
bit 15. If set to a bipolar range, it also expects a 2's complement
value, so the top bit of the sample value needs to be inverted in that
case.
Simplify the existing code by doing the 2's complement conversion after
the shift. That way, it is always bit 15 that is inverted regardless of
the resolution.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
drivers/staging/comedi/drivers/amplc_pci230.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/staging/comedi/drivers/amplc_pci230.c b/drivers/staging/comedi/drivers/amplc_pci230.c
index 7fa9c70..e4151d7 100644
--- a/drivers/staging/comedi/drivers/amplc_pci230.c
+++ b/drivers/staging/comedi/drivers/amplc_pci230.c
@@ -583,17 +583,16 @@ static inline unsigned short pci230_ao_mangle_datum(struct comedi_device *dev,
struct pci230_private *devpriv = dev->private;
/*
- * If a bipolar range was specified, mangle it
- * (straight binary->twos complement).
- */
- if (devpriv->ao_bipolar)
- datum ^= 1 << (thisboard->ao_bits - 1);
-
- /*
* PCI230 is 12 bit - stored in upper bits of 16 bit register (lower
* four bits reserved for expansion). PCI230+ is also 12 bit AO.
*/
datum <<= (16 - thisboard->ao_bits);
+ /*
+ * If a bipolar range was specified, mangle it
+ * (straight binary->twos complement).
+ */
+ if (devpriv->ao_bipolar)
+ datum ^= 0x8000;
return datum;
}
--
2.0.4
next prev parent reply other threads:[~2014-09-01 11:04 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-01 11:03 [PATCH 00/28] staging: comedi: more clean-up and remove legacy attach Ian Abbott
2014-09-01 11:03 ` [PATCH 01/28] staging: comedi: amplc_pci230: update MODULE_DESCRIPTION() Ian Abbott
2014-09-01 11:03 ` [PATCH 02/28] staging: comedi: amplc_pci230: don't use multiple blank lines Ian Abbott
2014-09-01 11:03 ` [PATCH 03/28] staging: comedi: amplc_pci230: remove some unnecessary parentheses Ian Abbott
2014-09-01 11:03 ` [PATCH 04/28] staging: comedi: amplc_pci230: collapse some 'else { if' chains Ian Abbott
2014-09-01 11:03 ` [PATCH 05/28] staging: comedi: amplc_pci230: remove "legacy" attach mechanism Ian Abbott
2014-09-01 11:03 ` [PATCH 06/28] staging: comedi: amplc_pci230: no need to manipulate PCI ref count Ian Abbott
2014-09-01 11:03 ` [PATCH 07/28] staging: comedi: amplc_pci230: set detach handler to comedi_pci_detach() Ian Abbott
2014-09-01 11:03 ` [PATCH 08/28] staging: comedi: amplc_pci230: absorb pci230_attach_common() Ian Abbott
2014-09-01 11:03 ` [PATCH 09/28] staging: comedi: amplc_pci230: no need to comedi_set_hw_dev() here Ian Abbott
2014-09-01 11:03 ` [PATCH 10/28] staging: comedi: amplc_pci230: absorb pci230_alloc_private() Ian Abbott
2014-09-01 11:03 ` [PATCH 11/28] staging: comedi: amplc_pci230: remove ai_chans member Ian Abbott
2014-09-01 11:03 ` [PATCH 12/28] staging: comedi: amplc_pci230: remove ao_chans member Ian Abbott
2014-09-01 11:03 ` [PATCH 13/28] staging: comedi: amplc_pci230: shrink struct pci230_board Ian Abbott
2014-09-01 11:03 ` Ian Abbott [this message]
2014-09-01 11:03 ` [PATCH 15/28] staging: comedi: amplc_pci230: simplify pci230_ai_read() Ian Abbott
2014-09-01 11:03 ` [PATCH 16/28] staging: comedi: amplc_pci230: remove 'inline' Ian Abbott
2014-09-01 11:03 ` [PATCH 17/28] staging: comedi: amplc_pci230: rename pci230_ai_rinsn() Ian Abbott
2014-09-01 11:03 ` [PATCH 18/28] staging: comedi: amplc_pci230: add `pci230_` prefix to functions Ian Abbott
2014-09-01 11:03 ` [PATCH 19/28] staging: comedi: amplc_pci230: use comedi_range_is_bipolar() Ian Abbott
2014-09-01 11:03 ` [PATCH 20/28] staging: comedi: amplc_pci230: make `intr_running` a bitfield Ian Abbott
2014-09-01 11:03 ` [PATCH 21/28] staging: comedi: amplc_pci230: replace `state` member with bitfields Ian Abbott
2014-09-01 11:03 ` [PATCH 22/28] staging: comedi: amplc_pci230: rewrite shared resource handling Ian Abbott
2014-09-01 11:03 ` [PATCH 23/28] staging: comedi: amplc_pci230: reduce indentation in pci230_ao_inttrig_scan_begin() Ian Abbott
2014-09-01 11:03 ` [PATCH 24/28] staging: comedi: amplc_pci230: reduce indentation in pci230_ao_start() Ian Abbott
2014-09-01 11:03 ` [PATCH 25/28] staging: comedi: amplc_pci230: reduce indentation in pci230_ai_inttrig_convert() Ian Abbott
2014-09-01 11:03 ` [PATCH 26/28] staging: comedi: amplc_pci230: reduce indentation in pci230_ai_start() Ian Abbott
2014-09-01 11:03 ` [PATCH 27/28] staging: comedi: amplc_pci230: change pci230_handle_ao_fifo() return type Ian Abbott
2014-09-01 11:04 ` [PATCH 28/28] staging: comedi: amplc_pci230: simplify interrupt enable handling Ian Abbott
2014-09-02 17:43 ` [PATCH 00/28] staging: comedi: more clean-up and remove legacy attach Hartley Sweeten
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