Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes:
> This modifies hardware flags for powersave to support three different
> flags:
> * IEEE80211_HW_SUPPORTS_PS - indicates general PS support
> * IEEE80211_HW_PS_NULLFUNC_STACK - indicates nullfunc/... handling in software
> * IEEE80211_HW_SUPPORTS_DYNAMIC_PS - indicates dynamic PS on the device
>
> It also adds documentation for all this which explains how to set the
> various flags.
Very good, this is just what was needed. I was planning to add similar
flags myself. Few comments though:
> + * @IEEE80211_HW_SUPPORTS_DYNAMIC_PS:
> + * Hardware has support for dynamic PS.
The "dynamic power save" was a very bad term, it seems that people
misunderstand it all the time. Maybe we should rename it to something
else? We can do it later, though.
> + * DOC: Powersave support
> + *
> + * mac80211 has support for various powersave implementations.
> + *
> + * First, it can support hardware that handles all powersaving by
> + * itself, such hardware should simply set the %IEEE80211_HW_SUPPORTS_PS
> + * hardware flag. In that case, it will be told about the desired
> + * powersave mode regardless of association status, and the driver or
> + * hardware must take care of enabling/disabling powersave depending on
> + * the association status and TIM bit and send nullfunc frames by
> + itself.
Actually I'm not aware of any hardware designs which enables and
disables power save according to association status (modulo fullmac
design, of course). Even iwlwifi, which I think has the most
sophisticated power save support, requires the host to enable power
save according to the association status. Hence I would like to have
the power save enable/disable logic based on association status in
mac80211.
We already have this support in ieee80211_set_associated()
[Reads the function again]
Or, actually we had it. I think Vivek's patch changed the
functionality. But anyway, it's very easy to add the support back.
The reason why I would like to have this in mac80211 is to avoid
having duplicate bugs in different drivers and make the driver
implementation easier.
> + * Additionally, such hardware may set the %IEEE80211_HW_SUPPORTS_DYNAMIC_PS
> + * flag to indicate that it can support dynamic PS mode (see below).
> + *
> + * Other hardware designs cannot send nullfunc frames by themselves and
> + * need to be told explicitly about powersave transitions depending on
> + * association status, need software support for parsing the TIM bitmap
> + * and can implement dynamic PS mode in software. This is also supported
> + * by mac80211 by combining the %IEEE80211_HW_SUPPORTS_PS and
> + * %IEEE80211_HW_PS_NULLFUNC_STACK flags.
stlc45xx (and p54spi) wakeup for multicast frames automatically, but
ath5/9k need the host to do it. I think we will need a separate flag
for that, but I can add it later.
> + * Dynamic powersave mode is an extension to normal powersave mode in which
> + * the hardware stays awake for a user-specified period of time after sending
> + * a frame so that reply frames need not be buffered and therefore delayed
> + * to the next wakeup. This can either be supported by hardware, in which case
> + * the driver needs to look at the @dynamic_ps_timeout hardware configuration
> + * value, or by the stack if all nullfunc handling is in the stack.
> + */
Good description of the feature. Hopefully people now better
understand what I meant with dynamic power save.
> @@ -858,8 +861,17 @@ static int ieee80211_ioctl_siwpower(stru
> if (wrq->flags & ~(IW_POWER_MODE | IW_POWER_TIMEOUT))
> return -EINVAL;
>
> - if (wrq->flags & IW_POWER_TIMEOUT)
> + if (wrq->flags & IW_POWER_TIMEOUT) {
> + /*
> + * dynamic PS only supported if nullfunc handling in stack
> + * or hardware supports dynamic PS itself
> + */
> + if (!(local->hw.flags & IEEE80211_HW_SUPPORTS_DYNAMIC_PS) &&
> + !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
> + return -EOPNOTSUPP;
> +
> timeout = wrq->value / 1000;
> + }
Actually there are hardware designs which don't have dynamic power
save but have null frame creation in firmware (and hence don't need
IEEE80211_HW_PS_NULLFUNC_STACK). So IEEE80211_HW_SUPPORTS_DYNAMIC_PS
and IEEE80211_HW_PS_NULLFUNC_STACK are not related to each other in
any way. I suspect at76_usb is such design, but I need to recheck
that.
So I would like to implement this so that if
IEEE80211_HW_SUPPORTS_DYNAMIC_PS is not set mac80211 will always use
it's own timer, independent of IEEE80211_HW_PS_NULLFUNC_STACK. If you
agree, I can create a separate patch for this.
--
Kalle Valo
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