Re: [PATCH v3 3/4] thermal: core: genetlink support for events/cmd/sampling

Daniel Lezcano
2020-07-05T10:54:45Z

On 05/07/2020 08:03, Zhang Rui wrote:
> On Fri, 2020-07-03 at 10:53 +0200, Daniel Lezcano wrote:
>> Initially the thermal framework had a very simple notification
>> mechanism to send generic netlink messages to the userspace.
>>
>> The notification function was never called from anywhere and the
>> corresponding dead code was removed. It was probably a first attempt
>> to introduce the netlink notification.
>>
>> At LPC2018, the presentation "Linux thermal: User kernel interface",
>> proposed to create the notifications to the userspace via a kfifo.
>>
>> The advantage of the kfifo is the performance. It is usually used
>> from
>> a 1:1 communication channel where a driver captures data and sends it
>> as fast as possible to a userspace process.
>>
>> The drawback is that only one process uses the notification channel
>> exclusively, thus no other process is allowed to use the channel to
>> get temperature or notifications.
>>
>> This patch defines a generic netlink API to discover the current
>> thermal setup and adds event notifications as well as temperature
>> sampling. As any genetlink protocol, it can evolve and the versioning
>> allows to keep the backward compatibility.
>>
>> In order to prevent the user from getting flooded with data on a
>> single channel, there are two multicast channels, one for the
>> temperature sampling when the thermal zone is updated and another one
>> for the events, so the user can get the events only without the
>> thermal zone temperature sampling.
>>
>> Also, a list of commands to discover the thermal setup is added and
>> can be extended when needed.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

[ ... ]

>> +static int thermal_genl_event_cdev_update(struct param *p)
>> +{
>> + if (nla_put_u32(p->msg, THERMAL_GENL_ATTR_CDEV_ID,
>> + p->cdev_id) ||
>> + nla_put_u32(p->msg, THERMAL_GENL_ATTR_CDEV_CUR_STATE,
>> + p->cdev_state) ||
>> + nla_put_u32(p->msg, THERMAL_GENL_ATTR_CDEV_MAX_STATE,
>> + p->cdev_max_state))
>> + return -EMSGSIZE;
>> +
>> + return 0;
>> +}
>
>> +int thermal_notify_cdev_update(int cdev_id, int cdev_state)
>>> +{
>>> + struct param p = { .cdev_id = cdev_id, .cdev_state = cdev_state
>>> };
>>
>
> .cdev_max_state is not set here.
> I think we need to add a second parameter for cdev_max_state when
> invoking thermal_nofify_cdev_update().

Ah, right. I forgot to add the parameter, thanks for pointing this out.

-- Daniel

[ ... ]

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