[RFC,1/2] wifi: wireless: warn on most wireless extension usage

From: Johannes Berg <johannes.berg@intel.com>

With MLO/EHT support around the corner, we're going to
remove support for wireless extensions with new devices
since MLO cannot be properly indicated using them.

Add a warning to indicate which processes are still
using wireless extensions, if being used with modern
(i.e. cfg80211) drivers.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/wireless/wext-core.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

Johannes Berg <johannes@sipsolutions.net> writes:

> From: Johannes Berg <johannes.berg@intel.com>
>
> With MLO/EHT support around the corner, we're going to
> remove support for wireless extensions with new devices
> since MLO cannot be properly indicated using them.
>
> Add a warning to indicate which processes are still
> using wireless extensions, if being used with modern
> (i.e. cfg80211) drivers.

I doubt people outside of wireless know what MLO or EHT are :) Also it
would be good to mention what's the replacement for wireless extensions
so better to spell out that as well. So maybe use more widely known
terminology like this:

"With Wi-Fi 7 (IEEE 802.11be) support around the corner, we're going to
remove support for wireless extensions with new devices since Multi-Link
Operation (MLO) feature cannot be properly indicated using them.

Add a warning to indicate which processes are still using the ancient
wireless extensions, if being used with modern (i.e. cfg80211) drivers.
All those users should be using nl80211 instead.

Ancient drivers, which are not using cfg80211, are unaffected."

> +#ifdef CONFIG_CFG80211_WEXT
> +static void wireless_warn_cfg80211_wext(void)
> +{
> +	char name[sizeof(current->comm)];
>  
> +	pr_warn_ratelimited("warning: `%s' uses wireless extensions that are deprecated for modern drivers\n",
> +			    get_task_comm(name, current));
> +}
> +#endif

Maybe add ", switch to nl80211" also to the warning message?

On Thu, 2022-11-17 at 12:48 +0200, Kalle Valo wrote:
> Johannes Berg <johannes@sipsolutions.net> writes:
> 
> > From: Johannes Berg <johannes.berg@intel.com>
> > 
> > With MLO/EHT support around the corner, we're going to
> > remove support for wireless extensions with new devices
> > since MLO cannot be properly indicated using them.
> > 
> > Add a warning to indicate which processes are still
> > using wireless extensions, if being used with modern
> > (i.e. cfg80211) drivers.
> 
> I doubt people outside of wireless know what MLO or EHT are :) Also it
> would be good to mention what's the replacement for wireless extensions
> so better to spell out that as well. So maybe use more widely known
> terminology like this:
> 
> "With Wi-Fi 7 (IEEE 802.11be) support around the corner, we're going to
> remove support for wireless extensions with new devices since Multi-Link
> Operation (MLO) feature cannot be properly indicated using them.
> 
> Add a warning to indicate which processes are still using the ancient
> wireless extensions, if being used with modern (i.e. cfg80211) drivers.
> All those users should be using nl80211 instead.
> 
> Ancient drivers, which are not using cfg80211, are unaffected."

Sure, makes sense I guess. This might become a more referenced commit
perhaps :-)

> > +#ifdef CONFIG_CFG80211_WEXT
> > +static void wireless_warn_cfg80211_wext(void)
> > +{
> > +	char name[sizeof(current->comm)];
> >  
> > +	pr_warn_ratelimited("warning: `%s' uses wireless extensions that are deprecated for modern drivers\n",
> > +			    get_task_comm(name, current));
> > +}
> > +#endif
> 
> Maybe add ", switch to nl80211" also to the warning message?
> 
It already got so long ... but I guess that makes sense.

johannes