Re: [PATCH] staging/comedi: fix sparse warning: shift too big
From: Ian Abbott
Date: Fri May 02 2014 - 16:37:24 EST
On 02/05/14 19:28, Hartley Sweeten wrote:
On Friday, May 02, 2014 9:50 AM, Ian Abbott wrote:
On 2014-05-02 15:57, Brilliantov Kirill Vladimirovich wrote:
Signed-off-by: Brilliantov Kirill Vladimirovich <brilliantov@xxxxxxxx>
---
drivers/staging/comedi/drivers/ni_stc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/drivers/ni_stc.h b/drivers/staging/comedi/drivers/ni_stc.h
index f0630b78..197b568 100644
--- a/drivers/staging/comedi/drivers/ni_stc.h
+++ b/drivers/staging/comedi/drivers/ni_stc.h
@@ -717,7 +717,7 @@ enum AI_AO_Select_Bits {
static inline unsigned ni_stc_dma_channel_select_bitfield(unsigned channel)
{
if (channel < 4)
- return 1 << channel;
+ return 1 << (channel & 0x3);
if (channel == 4)
return 0x3;
if (channel == 5)
The warning seems a bit spurious!
The whole mite.c driver and it's users are all a bit of a mess.
I did find the information about the "AI AO Select Register" in the National
Instruments PCI E Series manual:
-----
The AI AO Select Register contains 8 bits that control the logical DMA selection for the
analog input and analog output resources. The contents of this register are cleared upon power
up and after a reset condition.
Address: base address + 0x09
Type: write-only
Word size: 8-bit
Bit Name Description
7-4 Reserved Reserved-Always write 0 to these bits (for PCI-6032E
and PCI-6033E only).
7-4 Output<D..A> Analog Output Logical Channel D through A-These four
bits select the logical channels of the MITE to be used by
the analog output. You can only set one of these bits at a
time (except for the PCI-6032E and PCI-6033E).
3-0 Input<D..A> Analog Input Logical Channel D through A-These four
bits select the logical channels to be used by the analog
input. You can only set one of these bits at a time.
-----
Based on this the ni_stc_dma_channel_select_bitfield() function appears to be
incorrect. The "channel"s should only be in the range 0 to 3 and result in a returned
bitfield of:
channel bitfield Description
0 0x01 Analog Input or Output Channel A
1 0x02 Analog Input or Output Channel B
2 0x04 Analog Input or Output Channel C
3 0x08 Analog Input or Output Channel D
Just my two cents...
Apparently, the M-series cards have six DMA channels - two more than the
E-series cards. They must have decided to keep the existing bitfield
encoding for the first four channels for backwards compatibility, and
use special bitfield values for the extra channels.
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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