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From: Andrew Morton on 4 Aug 2010 19:40
On Thu, 5 Aug 2010 01:06:52 +0400
Alexander Gordeev <lasaine(a)lvk.cs.msu.su> wrote:

> Add parallel port PPS client. It uses a standard method for capturing
> timestamps for assert edge transitions: getting a timestamp soon after
> an interrupt has happened. This is not a very precise source of time
> information due to interrupt handling delays. However, timestamps for
> clear edge transitions are much more precise because the interrupt
> handler continuously polls hardware port until the transition is done.
> Hardware port operations require only about 1us so the maximum error
> should not exceed this value. This was my primary goal when developing
> this client.
> Clear edge capture could be disabled using clear_wait parameter.
>
>
> ...
>
> +
> +#define SIGNAL_IS_SET(port) \
> + ((port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0)

This could (and hence should) be implemented in a regular old C
function.

>
> ...
>
> +{
> + struct pps_client_pp *device;
> + struct pps_source_info info = {
> + .name = DRVNAME,
> + .path = "",
> + .mode = PPS_CAPTUREBOTH | \
> + PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
> + PPS_ECHOASSERT | PPS_ECHOCLEAR | \
> + PPS_CANWAIT | PPS_TSFMT_TSPEC,
> + .echo = pps_echo,
> + .owner = THIS_MODULE,
> + .dev = NULL
> + };
> +
> + device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
> + if (!device) {
> + pr_err(DRVNAME ": memory allocation failed, not attaching\n");
> + return;

eww. parport_driver.attach() returns void so there's no way to
propagate the error code back. That sucks a bit.

>
> ...
>
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From: Alexander Gordeev on 5 Aug 2010 08:50
В Wed, 4 Aug 2010 16:34:30 -0700
Andrew Morton <akpm(a)linux-foundation.org> пишет:

> On Thu, 5 Aug 2010 01:06:52 +0400
> Alexander Gordeev <lasaine(a)lvk.cs.msu.su> wrote:
>
> > Add parallel port PPS client. It uses a standard method for capturing
> > timestamps for assert edge transitions: getting a timestamp soon after
> > an interrupt has happened. This is not a very precise source of time
> > information due to interrupt handling delays. However, timestamps for
> > clear edge transitions are much more precise because the interrupt
> > handler continuously polls hardware port until the transition is done.
> > Hardware port operations require only about 1us so the maximum error
> > should not exceed this value. This was my primary goal when developing
> > this client.
> > Clear edge capture could be disabled using clear_wait parameter.
> >
> >
> > ...
> >
> > +
> > +#define SIGNAL_IS_SET(port) \
> > + ((port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0)
>
> This could (and hence should) be implemented in a regular old C
> function.

Ok, thanks!

> >
> > ...
> >
> > +{
> > + struct pps_client_pp *device;
> > + struct pps_source_info info = {
> > + .name = DRVNAME,
> > + .path = "",
> > + .mode = PPS_CAPTUREBOTH | \
> > + PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
> > + PPS_ECHOASSERT | PPS_ECHOCLEAR | \
> > + PPS_CANWAIT | PPS_TSFMT_TSPEC,
> > + .echo = pps_echo,
> > + .owner = THIS_MODULE,
> > + .dev = NULL
> > + };
> > +
> > + device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
> > + if (!device) {
> > + pr_err(DRVNAME ": memory allocation failed, not attaching\n");
> > + return;
>
> eww. parport_driver.attach() returns void so there's no way to
> propagate the error code back. That sucks a bit.

IMHO, the whole parport thing currently sucks quite a bit.

--
Alexander
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