Appeases the warning "parport0 (bw-qcam): use data_reverse for this!"

Signed-off-by: Brett T. Warden <brett.warden@gmail.com>

---

It seems to work fine with my Quickcam under 2.6.22.

diff --git a/drivers/media/video/bw-qcam.c b/drivers/media/video/bw-qcam.c
index 7d47cbe..01e47ed 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 +374,11 @@ static void qc_reset(struct qcam_device *q)
                        break;

                case QC_ANY:
-                       write_lpcontrol(q, 0x20);
+                       /*
+                        * Replaced with reverse_port
+                        * write_lpcontrol(q, 0x20);
+                        */
+                       reverse_port(q);
                        write_lpdata(q, 0x75);

                        if (read_lpdata(q) != 0x75) {
@@ -512,10 +521,12 @@ 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;
               ...
[ message continues ]

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.

Ray
-

[ message continues ]

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, ...
[ message continues ]

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...

Ray
-

[ message continues ]

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
-

[ message continues ]

Fixes use of parport_write_control() to match the newer interface that
requires explicit parport_data_reverse() and parport_data_forward()
calls. This eliminates the following error message and restores the
original intended behavior:

parport0 (bw-qcam): use data_reverse for this!

Also increases threshold in qc_detect() from 300 to 400, as my camera
often results in a count of approx 330. Added a kernel error message
to indicate detection failure.

Signed-off-by: Brett T. Warden <brett.warden@gmail.com>

---

Thanks Ray and Randy for your comments, and for pointing out that I
needed to reset the port to forward mode!

diff --git a/drivers/media/video/bw-qcam.c b/drivers/media/video/bw-qcam.c
index 7d47cbe..961e377 100644
--- a/drivers/media/video/bw-qcam.c
+++ b/drivers/media/video/bw-qcam.c
@@ -104,6 +104,17 @@ static inline void write_lpdata(struct
qcam_device *q, int d)

 static inline void write_lpcontrol(struct qcam_device *q, int d)
 {
+       if(0x20 & d) {
+               /* Set bidirectional mode to reverse (data in) */
+               parport_data_reverse(q->pport);
+       } else {
+               /* Set bidirectional mode to forward (data out) */
+               parport_data_forward(q->pport);
+       }
+
+       /* Now issue the regular port command, but strip out the
+        * direction flag */
+       d &= ~0x20;
        parport_write_control(q->pport, d);
 }

@@ -344,10 +355,13 @@ static int qc_detect(struct qcam_device *q)
        /* Be (even more) liberal in what you accept...  */

 /*     if (count > 30 && count < 200) */
-       if (count > 20 && count < 300)
+       if (count > 20 && count < 400)
+       {
                return 1;       /* found */
-       else
+       } else {
+               printk(KERN_ERR "No Quickcam found on port %s\n",
q->pport->name);
                return 0;       /* not found */
+       }
 }





-- 
Brett Warden
-

[ message continues ]

On Thu, 27 Sep 2007 12:28:31 -0700



Acked-by: Alan Cox <alan@redhat.com>
-

[ message continues ]

---
~Randy
Phaedrus says that Quality is about caring.
-

[ message continues ]