On 9/26/07, Ray Lee <[email protected]> wrote:
> On 9/26/07, Brett Warden <[email protected]> wrote:
> > On 9/26/07, Ray Lee <[email protected]> wrote:
> >
> > > Just as an aside, if you've tested this and it works, then there's no
> > > point to keep the write_lpcontrol even as a comment. Kill those four
> > > lines, and if someone's interested in what happened they'll just look
> > > at the file history.
> >
> > Point taken, thanks for the feedback.
> >
> > ---
> >
> > diff --git a/drivers/media/video/bw-qcam.c b/drivers/media/video/bw-qcam.c
> > index 7d47cbe..0ba92e3 100644
> > --- a/drivers/media/video/bw-qcam.c
> > +++ b/drivers/media/video/bw-qcam.c
> > @@ -107,6 +107,11 @@ static inline void write_lpcontrol(struct
> > qcam_device *q, int d)
> > parport_write_control(q->pport, d);
> > }
> >
> > +static inline void reverse_port(struct qcam_device *q)
> > +{
> > + parport_data_reverse(q->pport);
> > +}
> > +
> > static int qc_waithand(struct qcam_device *q, int val);
> > static int qc_command(struct qcam_device *q, int command);
> > static int qc_readparam(struct qcam_device *q);
> > @@ -369,7 +374,7 @@ static void qc_reset(struct qcam_device *q)
> > break;
> >
> > case QC_ANY:
> > - write_lpcontrol(q, 0x20);
> > + reverse_port(q);
> > write_lpdata(q, 0x75);
> >
> > if (read_lpdata(q) != 0x75) {
> > @@ -512,10 +517,12 @@ static inline int qc_readbytes(struct
> > qcam_device *q, char buffer[])
> > switch (q->port_mode & QC_MODE_MASK)
> > {
> > case QC_BIDIR: /* Bi-directional Port */
> > - write_lpcontrol(q, 0x26);
> > + reverse_port(q);
> > + write_lpcontrol(q, 0x6);
> > lo = (qc_waithand2(q, 1) >> 1);
> > hi = (read_lpstatus(q) >> 3) & 0x1f;
> > - write_lpcontrol(q, 0x2e);
> > + reverse_port(q);
> > + write_lpcontrol(q, 0xe);
> > lo2 = (qc_waithand2(q, 0) >> 1);
> > hi2 = (read_lpstatus(q) >> 3) & 0x1f;
> > switch (q->bpp)
> > @@ -613,10 +620,13 @@ static long qc_capture(struct qcam_device * q,
> > char __user *buf, unsigned long l
> >
> > if ((q->port_mode & QC_MODE_MASK) == QC_BIDIR)
> > {
> > - write_lpcontrol(q, 0x2e); /* turn port around */
> > - write_lpcontrol(q, 0x26);
> > + reverse_port(q); /* turn port around */
> > + write_lpcontrol(q, 0xe);
> > + reverse_port(q);
> > + write_lpcontrol(q, 0x6);
> > (void) qc_waithand(q, 1);
> > - write_lpcontrol(q, 0x2e);
> > + reverse_port(q);
> > + write_lpcontrol(q, 0xe);
> > (void) qc_waithand(q, 0);
> > }
>
> Better, and do you have time for two (possibly stupid) questions? In
> each of the last cases it looks like the transformation is from a
> write_lpcontrol -> reverse_port and a write_lpcontrol (old address -
> 0x20). Except the first one, which merely has the reverse_port. One
> would think that there should be a write_lpcontrol(q, 0x0); after that
> one.
>
> Also, is the reverse port sticky, or does it only apply to the next
> write? If it's only the next, then maybe a different name would be
> better. If it's sticky, then I think the code is wrong...
In response to Randy's and your questions, here's what I understand:
The error message comes from parport_pc_write_control in
include/linux/parport_pc.h, which is called by bw-qcam's
write_lpcontrol():
static __inline__ void parport_pc_write_control (struct parport *p,
unsigned char d)
{
const unsigned char wm = (PARPORT_CONTROL_STROBE |
PARPORT_CONTROL_AUTOFD |
PARPORT_CONTROL_INIT |
PARPORT_CONTROL_SELECT);
/* Take this out when drivers have adapted to newer interface. */
if (d & 0x20) {
printk (KERN_DEBUG "%s (%s): use data_reverse for this!\n",
p->name, p->cad->name);
parport_pc_data_reverse (p);
}
__parport_pc_frob_control (p, wm, d & wm);
}
The mask wm works out to 0x0f, so first it calls
parport_pc_data_reverse(), then masks off the high nibble with the
reverse flag and makes the regular call.
Looking at that more carefully, I'm not sure whether I need to add the
write_lpcontrol(q, 0) after the first call. Other than that, I believe
I'm following the same procedure.
As for whether data_reverse is sticky, I don't know... I'll see what I
can find out.
--
Brett Warden
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