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SubjectRe: [PATCHv3 15/16] pps: add parallel port PPS client
On Thu,  5 Aug 2010 01:06:52 +0400
Alexander Gordeev <lasaine@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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