[PATCH 3/5] tty/vt: add con_bind and con_unbind functions

[Paulo Zanoni]

2013/10/1 Ville Syrjälä <ville.syrjala at linux.intel.com>:
> On Thu, Sep 26, 2013 at 08:06:00PM -0300, Paulo Zanoni wrote:
>> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>
>> The consoles who need to do something when unbinding or binding can
>> optionally implement these functions.
>>
>> The current problem I'm trying to solve is that when i915+fbcon is
>> loaded on Haswell, if we disable the power well (to save power) the
>> VGA interface gets completely disabled, so when we unbind fbcon we
>> need to restore the VGA interface to allow vgacon to work.
>
> We don't need to make it work. No one else does, and in the general case
> it's even impossible since on some hardware that would definitely
> corrupt the state that the real driver is attempting to use. The only
> case where it might be nice to restore vgacon is on i915 unload, but no
> one else does that either AFAIK, so I would not waste any cycles on
> attempting that.

I don't understand your point. Without patches 3-4-5, module_reload
doesn't work at all if the power well is disabled: we need these
patches to fix it. The plan is not to restore everything to make
vgacon actually work, the plan is just to prevent it from breaking
module_reload.


>
>>
>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
>> ---
>>  drivers/tty/vt/vt.c     | 6 ++++++
>>  include/linux/console.h | 2 ++
>>  2 files changed, 8 insertions(+)
>>
>> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
>> index 9a8e8c5..beb5986 100644
>> --- a/drivers/tty/vt/vt.c
>> +++ b/drivers/tty/vt/vt.c
>> @@ -3014,6 +3014,9 @@ static int do_bind_con_driver(const struct consw *csw, int first, int last,
>>       if (retval)
>>               goto err;
>>
>> +     if (csw->con_bind)
>> +             csw->con_bind();
>> +
>>       if (!(con_driver->flag & CON_DRIVER_FLAG_INIT)) {
>>               csw->con_startup();
>>               con_driver->flag |= CON_DRIVER_FLAG_INIT;
>> @@ -3152,6 +3155,9 @@ int do_unbind_con_driver(const struct consw *csw, int first, int last, int deflt
>>       if (!con_is_bound(csw))
>>               goto err;
>>
>> +     if (csw->con_unbind)
>> +             csw->con_unbind();
>> +
>>       first = max(first, con_driver->first);
>>       last = min(last, con_driver->last);
>>
>> diff --git a/include/linux/console.h b/include/linux/console.h
>> index 7571a16..5cd2c35 100644
>> --- a/include/linux/console.h
>> +++ b/include/linux/console.h
>> @@ -65,6 +65,8 @@ struct consw {
>>        * Restore the console to its pre-debug state as closely as possible.
>>        */
>>       int     (*con_debug_leave)(struct vc_data *);
>> +     void    (*con_bind)(void);
>> +     void    (*con_unbind)(void);
>>  };
>>
>>  extern const struct consw *conswitchp;
>> --
>> 1.8.3.1
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Ville Syrjälä
> Intel OTC



-- 
Paulo Zanoni