RE: [PATCH v4 2/2] PTP: add support for one-shot output

[Keller, Jacob E]

> -----Original Message-----
> From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-owner@xxxxxxxxxxxxxxx] On
> Behalf Of Felipe Balbi
> Sent: Tuesday, September 10, 2019 11:16 PM
> To: Richard Cochran <richardcochran@xxxxxxxxx>
> Cc: Hall, Christopher S <christopher.s.hall@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> Subject: [PATCH v4 2/2] PTP: add support for one-shot output
> 
> Some controllers allow for a one-shot output pulse, in contrast to
> periodic output. Now that we have extensible versions of our IOCTLs, we
> can finally make use of the 'flags' field to pass a bit telling driver
> that if we want one-shot pulse output.
> 
> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> ---
> 
> Changes since v3:
> 	- Remove bogus bitwise negation
> 
> Changes since v2:
> 	- Add _PEROUT_ to bit macro
> 
> Changes since v1:
> 	- remove comment from .flags field
> 
>  include/uapi/linux/ptp_clock.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
> index 9a0af3511b68..f16301015949 100644
> --- a/include/uapi/linux/ptp_clock.h
> +++ b/include/uapi/linux/ptp_clock.h
> @@ -38,8 +38,8 @@
>  /*
>   * Bits of the ptp_perout_request.flags field:
>   */
> -#define PTP_PEROUT_VALID_FLAGS (0)
> -
> +#define PTP_PEROUT_ONE_SHOT (1<<0)
> +#define PTP_PEROUT_VALID_FLAGS	(PTP_PEROUT_ONE_SHOT)
>  /*
>   * struct ptp_clock_time - represents a time value
>   *
> @@ -77,7 +77,7 @@ struct ptp_perout_request {
>  	struct ptp_clock_time start;  /* Absolute start time. */
>  	struct ptp_clock_time period; /* Desired period, zero means disable. */
>  	unsigned int index;           /* Which channel to configure. */
> -	unsigned int flags;           /* Reserved for future use. */
> +	unsigned int flags;
>  	unsigned int rsv[4];          /* Reserved for future use. */
>  };
> 
> --
> 2.23.0

Hi Felipe,

Do you have any examples for how you envision using this? I don't see any drivers or other code on the list for doing so.

Additionally, it seems weird because we do not have support for specifying the pulse width. I guess you leave that up to driver choice?

Thanks,
Jake