[PATCH 02/12] drivers/gpio: provide optional timestamped readouts

Jan Kiszka jan.kiszka at siemens.com
Fri Jan 25 10:23:19 CET 2019


On 25.01.19 10:15, Philippe Gerum wrote:
> On 1/24/19 7:17 PM, Jan Kiszka wrote:
>> On 24.01.19 16:34, Philippe Gerum wrote:
>>> In timestamping mode, read() returns the timestamp of the latest event
>>> receipt on the pin based on CLOCK_MONOTONIC, along with the pin
>>> state. This is an optional pin readout mode controlled by the
>>> GPIO_RTIOC_TS request, e.g.:
>>>
>>> struct rtdm_gpio_readout rdo;
>>> int ret, on, val;
>>>
>>> on = 1;
>>> ret = ioctl(pinfd, GPIO_RTIOC_TS, &on);
>>> ret = read(pinfd, &rdo, sizeof(rdo));
>>> /* pin state changed to rdo.value at time rdo.timestamp */
>>>
>>> on = 0;
>>> ret = ioctl(pinfd, GPIO_RTIOC_TS, &on);
>>> ret = read(pinfd, &val, sizeof(val));
>>> /* pin state changed to value (time of change unspecified) */
>>>
>>> By default, timestamping mode is disabled, which corresponds to the
>>> original behavior.
>>>
>>> Signed-off-by: Philippe Gerum <rpm at xenomai.org>
>>> ---
>>>    include/cobalt/kernel/rtdm/gpio.h |  1 +
>>>    include/rtdm/uapi/gpio.h          | 18 +++++++----
>>>    kernel/drivers/gpio/gpio-core.c   | 54 +++++++++++++++++++++++--------
>>>    3 files changed, 54 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/include/cobalt/kernel/rtdm/gpio.h
>>> b/include/cobalt/kernel/rtdm/gpio.h
>>> index cdb472f8a..00055ec0a 100644
>>> --- a/include/cobalt/kernel/rtdm/gpio.h
>>> +++ b/include/cobalt/kernel/rtdm/gpio.h
>>> @@ -33,6 +33,7 @@ struct rtdm_gpio_pin {
>>>        rtdm_event_t event;
>>>        char *name;
>>>        struct gpio_desc *desc;
>>> +    nanosecs_abs_t timestamp;
>>>    };
>>>      struct rtdm_gpio_chip {
>>> diff --git a/include/rtdm/uapi/gpio.h b/include/rtdm/uapi/gpio.h
>>> index b745f156c..ac14be66c 100644
>>> --- a/include/rtdm/uapi/gpio.h
>>> +++ b/include/rtdm/uapi/gpio.h
>>> @@ -18,12 +18,18 @@
>>>    #ifndef _RTDM_UAPI_GPIO_H
>>>    #define _RTDM_UAPI_GPIO_H
>>>    -#define GPIO_RTIOC_DIR_OUT        _IOW(RTDM_CLASS_GPIO, 0, int)
>>> -#define GPIO_RTIOC_DIR_IN        _IO(RTDM_CLASS_GPIO, 1)
>>> -#define GPIO_RTIOC_IRQEN        _IOW(RTDM_CLASS_GPIO, 2, int) /* GPIO
>>> trigger */
>>> -#define GPIO_RTIOC_IRQDIS        _IO(RTDM_CLASS_GPIO, 3)
>>> -#define GPIO_RTIOC_REQS                _IO(RTDM_CLASS_GPIO, 4)
>>> -#define GPIO_RTIOC_RELS                _IO(RTDM_CLASS_GPIO, 5)
>>> +struct rtdm_gpio_readout {
>>> +    __u64 timestamp;
>>
>> nanosecs_abs_t - we use this type also in to userspace interface.
>>
> 
> Nope. This is ABI stuff, nanosecs_abs_t is not guaranteed to have the
> same size regardless of the ABI models, which is unsafe in mixed 32/64
> model configurations. OTOH, __u64 is safe.

If nanosecs_abs_t is alread an ABI, and it is used as such for a long time (see 
include/rtdm/uapi/serial.h). If you see a bug in its definition, that needs to 
be fixed. We should not resolve that by choosing open-coded local workarounds.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux



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