Messages in this thread | | | Date | Wed, 26 Sep 2007 14:43:22 -0700 | From | "Brett Warden" <> | Subject | Re: [PATCH] bw-qcam: use data_reverse instead of manually poking the control register |
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On 9/26/07, Ray Lee <ray-lk@madrabbit.org> wrote: > On 9/26/07, Brett Warden <brett.warden@gmail.com> wrote: > > On 9/26/07, Ray Lee <ray-lk@madrabbit.org> 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.
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