2012-06-13 22:42:55

by Hartley Sweeten

Subject: [PATCH 12/15] staging: comedi: 8255: refactor subdev_8255_insn function

Refactor the subdev_8255_insn function to follow what the user
space library is doing.

1) This function requires 'data' to contain 2 parameters. Add a
sanity check for this (insn->n != 2).

2) The 'data' parameters are actually a 'mask' of the valid bits and
the actual 'bits' to modify. Create local variables of these names
to help with maintainability.

3) The value returned in data[1] reflects the actual state of the
8255 io pins after the update of the masked bits. Fetch this data
in a local variable and then set data[1].

4) The user space library only checks for a < 0 return to indicate
an error. It appears that the 'return 2' in this function is supposed
to indicate the number of data parameters used to perform the command.
Return the insn->n value for this, the open coded '2' looks wrong.

Signed-off-by: H Hartley Sweeten <[email protected]>
Cc: Iam Abbott <[email protected]>
Cc: Frank Mori Hess <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
---
drivers/staging/comedi/drivers/8255.c | 42 +++++++++++++++++++++-----------
1 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/comedi/drivers/8255.c b/drivers/staging/comedi/drivers/8255.c
index 1f4b24c..da374de 100644
--- a/drivers/staging/comedi/drivers/8255.c
+++ b/drivers/staging/comedi/drivers/8255.c
@@ -135,26 +135,38 @@ static int subdev_8255_insn(struct comedi_device *dev,
{
struct subdev_8255_private *spriv = s->private;
unsigned long iobase = spriv->iobase;
+ unsigned int mask;
+ unsigned int bits;
+ unsigned int v;
+
+ if (insn->n != 2)
+ return -EINVAL;

- if (data[0]) {
- s->state &= ~data[0];
- s->state |= (data[0] & data[1]);
+ mask = data[0];
+ bits = data[1];

- if (data[0] & 0xff)
- spriv->io(1, _8255_DATA, s->state & 0xff, iobase);
- if (data[0] & 0xff00)
- spriv->io(1, _8255_DATA + 1,
- (s->state >> 8) & 0xff, iobase);
- if (data[0] & 0xff0000)
- spriv->io(1, _8255_DATA + 2,
- (s->state >> 16) & 0xff, iobase);
+ if (mask) {
+ v = s->state;
+ v &= ~mask;
+ v |= (bits & mask);
+
+ if (mask & 0xff)
+ spriv->io(1, _8255_DATA, v & 0xff, iobase);
+ if (mask & 0xff00)
+ spriv->io(1, _8255_DATA + 1, (v >> 8) & 0xff, iobase);
+ if (mask & 0xff0000)
+ spriv->io(1, _8255_DATA + 2, (v >> 16) & 0xff, iobase);
+
+ s->state = v;
}

- data[1] = spriv->io(0, _8255_DATA, 0, iobase);
- data[1] |= (spriv->io(0, _8255_DATA + 1, 0, iobase) << 8);
- data[1] |= (spriv->io(0, _8255_DATA + 2, 0, iobase) << 16);
+ v = spriv->io(0, _8255_DATA, 0, iobase);
+ v |= (spriv->io(0, _8255_DATA + 1, 0, iobase) << 8);
+ v |= (spriv->io(0, _8255_DATA + 2, 0, iobase) << 16);
+
+ data[1] = v;

- return 2;
+ return insn->n;
}

static void do_config(struct comedi_device *dev, struct comedi_subdevice *s)
--
1.7.7

2012-06-14 09:04:04

by Ian Abbott

Subject: Re: [PATCH 12/15] staging: comedi: 8255: refactor subdev_8255_insn function

On 2012/06/13 11:42 PM, H Hartley Sweeten wrote:
> Refactor the subdev_8255_insn function to follow what the user
> space library is doing.
>
> 1) This function requires 'data' to contain 2 parameters. Add a
> sanity check for this (insn->n != 2).

Actually, the comedi core will have already checked that.

> 4) The user space library only checks for a < 0 return to indicate
> an error. It appears that the 'return 2' in this function is supposed
> to indicate the number of data parameters used to perform the command.
> Return the insn->n value for this, the open coded '2' looks wrong.

As long as it still returns 2, I don't care how you do it!

--
-=( Ian Abbott @ MEV Ltd. E-mail: <[email protected]> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-