Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, 2017-07-25 at 17:50 +0200, Daniel Vetter wrote: > On Tue, Jul 25, 2017 at 03:18:04PM +0300, Paul Kocialkowski wrote: > > On Tue, 2017-07-25 at 10:16 +0200, Daniel Vetter wrote: > > > On Tue, Jul 25, 2017 at 10:58:55AM +0300, Paul Kocialkowski wrote: > > > > On Tue, 2017-07-25 at 09:34 +0200, Daniel Vetter wrote: > > > > > On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski > > > > > wrote: > > > > > > On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote: > > > > > > > On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul > > > > > > > Kocialkowski > > > > > > > wrote: > > > > > > > > This adds a common drm helper to detect whether the EDID > > > > > > > > changed > > > > > > > > from > > > > > > > > the last known cached one. This is useful help detect > > > > > > > > that a > > > > > > > > monitor > > > > > > > > was > > > > > > > > changed during a suspend/resume cycle. > > > > > > > > > > > > > > > > When that happens (a monitor is replaced by another one > > > > > > > > during > > > > > > > > suspend), > > > > > > > > no hotplug event will be triggered so the change will > > > > > > > > not be > > > > > > > > caught > > > > > > > > at > > > > > > > > resume time. Detecting that the EDID changed allows > > > > > > > > detecting > > > > > > > > it. > > > > > > > > > > > > > > > > Signed-off-by: Paul Kocialkowski > > > > > > > x.in > > > > > > > > tel. > > > > > > > > com> > > > > > > > > > > > > > > I can't find the older mails I've typed about this, but > > > > > > > the > > > > > > > plan > > > > > > > we've > > > > > > > discussed a while back was: > > > > > > > - Add a generational counter to each connector, maybe even > > > > > > > expose > > > > > > > it > > > > > > > to > > > > > > > userspace. > > > > > > > > > > > > > > - Increment that counter every time something changed, > > > > > > > e.g. > > > > > > > connector->status in the propbe helpers, or when > > > > > > > attaching a > > > > > > > new > > > > > > > edid > > > > > > > with the set_edid helper. > > > > > > > > > > > > > > - Tada, no changes needed to drivers, and easily > > > > > > > extensible to > > > > > > > other > > > > > > > things than edid! > > > > > > > > > > > > I don't see how it solves the problem here though. After a > > > > > > suspend/resume cycle, there is simply no indication that > > > > > > anything > > > > > > has > > > > > > changed when a monitor was replaced by another one, so I > > > > > > don't > > > > > > see > > > > > > how > > > > > > adding a counter in the mix would help. > > > > > > > > > > > > Could you provide more details about the reasoning? I feel > > > > > > like > > > > > > I'm > > > > > > missing something here. > > > > > > > > > > Your bug doesn't just exist over s/r, it's just much easier to > > > > > observe > > > > > in s/r since users can take however long they want to with > > > > > plugging in > > > > > a different monitor. But the same issue exists e.g. when we go > > > > > from > > > > > hpd to polling because too much noise on the line. > > > > > > > > > > Wrt the suspend/resume issue: What we need to do on resume is > > > > > do a > > > > > full reprobe of all outputs, in an async worker. Telling > > > > > userspace > > > > > to > > > > > do this by sending an uevent was the cheapest way, but it'd be > > > > > better > > > > > if the kernel could do that asynchronously and inform > > > > > userspace > > > > > about > > > > > the exact changes. And there's more to reprobe than just the > > > > > edid, > > > > > and > > > > > we don't want to re-invent a separate reprobe path just for > > > > > resume > > > > > like you start in your patch series. So yeah my plan was > > > > > missing: > > > > > > > > > > - force a full async reprobe after resume (maybe we could > > > > > reuse > > > > > the > > > > > poll worker for that as a one-shot). > > > > > > > > First off, I definitely agree we need a way to tell userspace > > > > exactly > > > > what has happened. I wanted to start a discussion about that in > > > > i-g- > > > > t > > > > patch "Unrelated hotplug uevent masking out actual test result" > > > > but > > > > it > > > > didn't get much traction. For testing purposes, it is > > > > unacceptable > > > > that > > > > userspace only gets notified that "something happened". > > > > > > > > Still, as far as I know, userspace is expected to ask for a full > > > > reprobe > > > > when something has changed, and that is apparently part of the > > > > DRM > > > > spec, > > > > so we can't expect that it could query for an update on "only > > > > the > > > > things > > > > that changed". > > > > > > We can update that spec in a backwards compatible way. E.g. we can > > > ask > > > for > > > the current properties without forcing a reprobe (won't even call > > > down > > > into the driver), and userspace could use that to check which > > > connector > > > has an incremented epoche counter since the last time it sampled > > > things. > > > Then it can reprobe just that on
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On 2017-07-24 10:54 AM, Paul Kocialkowski wrote:
> This adds a common drm helper to detect whether the EDID changed from
> the last known cached one. This is useful help detect that a monitor was
> changed during a suspend/resume cycle.
>
> When that happens (a monitor is replaced by another one during suspend),
> no hotplug event will be triggered so the change will not be caught at
> resume time. Detecting that the EDID changed allows detecting it.
>
This makes sense and could be used by other drivers.
Acked-by: Harry Wentland
Harry
> Signed-off-by: Paul Kocialkowski
> ---
> drivers/gpu/drm/drm_edid.c | 45 +
> include/drm/drm_edid.h | 3 +++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 6bb6337be920..f6ce8bc2907a 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct drm_connector
> *connector,
> }
> return;
> }
> +
> +/**
> + * drm_check_edid_changed - Check whether the EDID changed since the last
> update
> + * @connector: connector we're probing
> + * @adapter: I2C adapter to use for DDC
> + *
> + * Check whether the EDID changed since the last time it was updated in the
> + * drm blob cache.
> + *
> + * Return: A boolean indicating whether a change happened or not.
> + */
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter)
> +{
> + struct drm_property_blob *edid_blob;
> + struct edid *edid_stored;
> + struct edid *edid_read;
> + int ret = 0;
> +
> + if (!connector->edid_blob_ptr)
> + return false;
> +
> + edid_blob = drm_property_blob_get(connector->edid_blob_ptr);
> + if (!edid_blob)
> + return false;
> +
> + if (!edid_blob->data || edid_blob->length != sizeof(struct edid))
> + goto out;
> +
> + edid_stored = (struct edid *) edid_blob->data;
> +
> + edid_read = drm_get_edid(connector, adapter);
> + if (!edid_read)
> + goto out;
> +
> + ret = memcmp(edid_stored, edid_read, sizeof(struct edid));
> +
> + kfree(edid_read);
> +
> +out:
> + drm_property_blob_put(edid_blob);
> +
> + return ret != 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_check_edid_changed);
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 1e1908a6b1d6..593a97b269c3 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -485,4 +485,7 @@ void drm_edid_get_monitor_name(struct edid *edid, char
> *name,
> struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
> int hsize, int vsize, int fresh,
> bool rb);
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter);
> +
> #endif /* __DRM_EDID_H__ */
>
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote:
> This adds a common drm helper to detect whether the EDID changed from
> the last known cached one. This is useful help detect that a monitor was
> changed during a suspend/resume cycle.
>
> When that happens (a monitor is replaced by another one during suspend),
> no hotplug event will be triggered so the change will not be caught at
> resume time. Detecting that the EDID changed allows detecting it.
>
> Signed-off-by: Paul Kocialkowski
I can't find the older mails I've typed about this, but the plan we've
discussed a while back was:
- Add a generational counter to each connector, maybe even expose it to
userspace.
- Increment that counter every time something changed, e.g.
connector->status in the propbe helpers, or when attaching a new edid
with the set_edid helper.
- Tada, no changes needed to drivers, and easily extensible to other
things than edid!
Cheers, Daniel
> ---
> drivers/gpu/drm/drm_edid.c | 45 +
> include/drm/drm_edid.h | 3 +++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 6bb6337be920..f6ce8bc2907a 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct drm_connector
> *connector,
> }
> return;
> }
> +
> +/**
> + * drm_check_edid_changed - Check whether the EDID changed since the last
> update
> + * @connector: connector we're probing
> + * @adapter: I2C adapter to use for DDC
> + *
> + * Check whether the EDID changed since the last time it was updated in the
> + * drm blob cache.
> + *
> + * Return: A boolean indicating whether a change happened or not.
> + */
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter)
> +{
> + struct drm_property_blob *edid_blob;
> + struct edid *edid_stored;
> + struct edid *edid_read;
> + int ret = 0;
> +
> + if (!connector->edid_blob_ptr)
> + return false;
> +
> + edid_blob = drm_property_blob_get(connector->edid_blob_ptr);
> + if (!edid_blob)
> + return false;
> +
> + if (!edid_blob->data || edid_blob->length != sizeof(struct edid))
> + goto out;
> +
> + edid_stored = (struct edid *) edid_blob->data;
> +
> + edid_read = drm_get_edid(connector, adapter);
> + if (!edid_read)
> + goto out;
> +
> + ret = memcmp(edid_stored, edid_read, sizeof(struct edid));
> +
> + kfree(edid_read);
> +
> +out:
> + drm_property_blob_put(edid_blob);
> +
> + return ret != 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_check_edid_changed);
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 1e1908a6b1d6..593a97b269c3 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -485,4 +485,7 @@ void drm_edid_get_monitor_name(struct edid *edid, char
> *name,
> struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
> int hsize, int vsize, int fresh,
> bool rb);
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter);
> +
> #endif /* __DRM_EDID_H__ */
> --
> 2.13.2
>
> ___
> dri-devel mailing list
> dri-de...@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote:
> On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote:
> > This adds a common drm helper to detect whether the EDID changed
> > from
> > the last known cached one. This is useful help detect that a monitor
> > was
> > changed during a suspend/resume cycle.
> >
> > When that happens (a monitor is replaced by another one during
> > suspend),
> > no hotplug event will be triggered so the change will not be caught
> > at
> > resume time. Detecting that the EDID changed allows detecting it.
> >
> > Signed-off-by: Paul Kocialkowski
>
> I can't find the older mails I've typed about this, but the plan we've
> discussed a while back was:
> - Add a generational counter to each connector, maybe even expose it
> to
> userspace.
>
> - Increment that counter every time something changed, e.g.
> connector->status in the propbe helpers, or when attaching a new
> edid
> with the set_edid helper.
>
> - Tada, no changes needed to drivers, and easily extensible to other
> things than edid!
I don't see how it solves the problem here though. After a
suspend/resume cycle, there is simply no indication that anything has
changed when a monitor was replaced by another one, so I don't see how
adding a counter in the mix would help.
Could you provide more details about the reasoning? I feel like I'm
missing something here.
Cheers,
Paul
> > ---
> > drivers/gpu/drm/drm_edid.c | 45
> > +
> > include/drm/drm_edid.h | 3 +++
> > 2 files changed, 48 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 6bb6337be920..f6ce8bc2907a 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct
> > drm_connector *connector,
> > }
> > return;
> > }
> > +
> > +/**
> > + * drm_check_edid_changed - Check whether the EDID changed since
> > the last update
> > + * @connector: connector we're probing
> > + * @adapter: I2C adapter to use for DDC
> > + *
> > + * Check whether the EDID changed since the last time it was
> > updated in the
> > + * drm blob cache.
> > + *
> > + * Return: A boolean indicating whether a change happened or not.
> > + */
> > +bool drm_check_edid_changed(struct drm_connector *connector,
> > + struct i2c_adapter *adapter)
> > +{
> > + struct drm_property_blob *edid_blob;
> > + struct edid *edid_stored;
> > + struct edid *edid_read;
> > + int ret = 0;
> > +
> > + if (!connector->edid_blob_ptr)
> > + return false;
> > +
> > + edid_blob = drm_property_blob_get(connector-
> > >edid_blob_ptr);
> > + if (!edid_blob)
> > + return false;
> > +
> > + if (!edid_blob->data || edid_blob->length != sizeof(struct
> > edid))
> > + goto out;
> > +
> > + edid_stored = (struct edid *) edid_blob->data;
> > +
> > + edid_read = drm_get_edid(connector, adapter);
> > + if (!edid_read)
> > + goto out;
> > +
> > + ret = memcmp(edid_stored, edid_read, sizeof(struct edid));
> > +
> > + kfree(edid_read);
> > +
> > +out:
> > + drm_property_blob_put(edid_blob);
> > +
> > + return ret != 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_check_edid_changed);
> > diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> > index 1e1908a6b1d6..593a97b269c3 100644
> > --- a/include/drm/drm_edid.h
> > +++ b/include/drm/drm_edid.h
> > @@ -485,4 +485,7 @@ void drm_edid_get_monitor_name(struct edid
> > *edid, char *name,
> > struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
> >int hsize, int vsize,
> > int fresh,
> >bool rb);
> > +bool drm_check_edid_changed(struct drm_connector *connector,
> > + struct i2c_adapter *adapter);
> > +
> > #endif /* __DRM_EDID_H__ */
> > --
> > 2.13.2
> >
> > ___
> > dri-devel mailing list
> > dri-de...@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>
--
Paul Kocialkowski
Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo, Finland
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski
wrote:
> On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote:
>> On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote:
>> > This adds a common drm helper to detect whether the EDID changed
>> > from
>> > the last known cached one. This is useful help detect that a monitor
>> > was
>> > changed during a suspend/resume cycle.
>> >
>> > When that happens (a monitor is replaced by another one during
>> > suspend),
>> > no hotplug event will be triggered so the change will not be caught
>> > at
>> > resume time. Detecting that the EDID changed allows detecting it.
>> >
>> > Signed-off-by: Paul Kocialkowski
>>
>> I can't find the older mails I've typed about this, but the plan we've
>> discussed a while back was:
>> - Add a generational counter to each connector, maybe even expose it
>> to
>> userspace.
>>
>> - Increment that counter every time something changed, e.g.
>> connector->status in the propbe helpers, or when attaching a new
>> edid
>> with the set_edid helper.
>>
>> - Tada, no changes needed to drivers, and easily extensible to other
>> things than edid!
>
> I don't see how it solves the problem here though. After a
> suspend/resume cycle, there is simply no indication that anything has
> changed when a monitor was replaced by another one, so I don't see how
> adding a counter in the mix would help.
>
> Could you provide more details about the reasoning? I feel like I'm
> missing something here.
Your bug doesn't just exist over s/r, it's just much easier to observe
in s/r since users can take however long they want to with plugging in
a different monitor. But the same issue exists e.g. when we go from
hpd to polling because too much noise on the line.
Wrt the suspend/resume issue: What we need to do on resume is do a
full reprobe of all outputs, in an async worker. Telling userspace to
do this by sending an uevent was the cheapest way, but it'd be better
if the kernel could do that asynchronously and inform userspace about
the exact changes. And there's more to reprobe than just the edid, and
we don't want to re-invent a separate reprobe path just for resume
like you start in your patch series. So yeah my plan was missing:
- force a full async reprobe after resume (maybe we could reuse the
poll worker for that as a one-shot).
Cheers, Daniel
>
> Cheers,
>
> Paul
>
>> > ---
>> > drivers/gpu/drm/drm_edid.c | 45
>> > +
>> > include/drm/drm_edid.h | 3 +++
>> > 2 files changed, 48 insertions(+)
>> >
>> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> > index 6bb6337be920..f6ce8bc2907a 100644
>> > --- a/drivers/gpu/drm/drm_edid.c
>> > +++ b/drivers/gpu/drm/drm_edid.c
>> > @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct
>> > drm_connector *connector,
>> > }
>> > return;
>> > }
>> > +
>> > +/**
>> > + * drm_check_edid_changed - Check whether the EDID changed since
>> > the last update
>> > + * @connector: connector we're probing
>> > + * @adapter: I2C adapter to use for DDC
>> > + *
>> > + * Check whether the EDID changed since the last time it was
>> > updated in the
>> > + * drm blob cache.
>> > + *
>> > + * Return: A boolean indicating whether a change happened or not.
>> > + */
>> > +bool drm_check_edid_changed(struct drm_connector *connector,
>> > + struct i2c_adapter *adapter)
>> > +{
>> > + struct drm_property_blob *edid_blob;
>> > + struct edid *edid_stored;
>> > + struct edid *edid_read;
>> > + int ret = 0;
>> > +
>> > + if (!connector->edid_blob_ptr)
>> > + return false;
>> > +
>> > + edid_blob = drm_property_blob_get(connector-
>> > >edid_blob_ptr);
>> > + if (!edid_blob)
>> > + return false;
>> > +
>> > + if (!edid_blob->data || edid_blob->length != sizeof(struct
>> > edid))
>> > + goto out;
>> > +
>> > + edid_stored = (struct edid *) edid_blob->data;
>> > +
>> > + edid_read = drm_get_edid(connector, adapter);
>> > + if (!edid_read)
>> > + goto out;
>> > +
>> > + ret = memcmp(edid_stored, edid_read, sizeof(struct edid));
>> > +
>> > + kfree(edid_read);
>> > +
>> > +out:
>> > + drm_property_blob_put(edid_blob);
>> > +
>> > + return ret != 0;
>> > +}
>> > +EXPORT_SYMBOL_GPL(drm_check_edid_changed);
>> > diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
>> > index 1e1908a6b1d6..593a97b269c3 100644
>> > --- a/include/drm/drm_edid.h
>> > +++ b/include/drm/drm_edid.h
>> > @@ -485,4 +485,7 @@ void drm_edid_get_monitor_name(struct edid
>> > *edid, char *name,
>> > struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
>> >int hsize, int vsize,
>> > int fresh,
>> >bool rb);
>> > +bool drm_check_edid_changed(struct drm_connector *connector,
>> > + struct i2c_adapter *adapter);
>> > +
>> > #endif /* __DRM_EDID_H__ */
>
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, 2017-07-25 at 09:34 +0200, Daniel Vetter wrote: > On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski > wrote: > > On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote: > > > On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote: > > > > This adds a common drm helper to detect whether the EDID changed > > > > from > > > > the last known cached one. This is useful help detect that a > > > > monitor > > > > was > > > > changed during a suspend/resume cycle. > > > > > > > > When that happens (a monitor is replaced by another one during > > > > suspend), > > > > no hotplug event will be triggered so the change will not be > > > > caught > > > > at > > > > resume time. Detecting that the EDID changed allows detecting > > > > it. > > > > > > > > Signed-off-by: Paul Kocialkowski > > > com> > > > > > > I can't find the older mails I've typed about this, but the plan > > > we've > > > discussed a while back was: > > > - Add a generational counter to each connector, maybe even expose > > > it > > > to > > > userspace. > > > > > > - Increment that counter every time something changed, e.g. > > > connector->status in the propbe helpers, or when attaching a new > > > edid > > > with the set_edid helper. > > > > > > - Tada, no changes needed to drivers, and easily extensible to > > > other > > > things than edid! > > > > I don't see how it solves the problem here though. After a > > suspend/resume cycle, there is simply no indication that anything > > has > > changed when a monitor was replaced by another one, so I don't see > > how > > adding a counter in the mix would help. > > > > Could you provide more details about the reasoning? I feel like I'm > > missing something here. > > Your bug doesn't just exist over s/r, it's just much easier to observe > in s/r since users can take however long they want to with plugging in > a different monitor. But the same issue exists e.g. when we go from > hpd to polling because too much noise on the line. > > Wrt the suspend/resume issue: What we need to do on resume is do a > full reprobe of all outputs, in an async worker. Telling userspace to > do this by sending an uevent was the cheapest way, but it'd be better > if the kernel could do that asynchronously and inform userspace about > the exact changes. And there's more to reprobe than just the edid, and > we don't want to re-invent a separate reprobe path just for resume > like you start in your patch series. So yeah my plan was missing: > > - force a full async reprobe after resume (maybe we could reuse the > poll worker for that as a one-shot). First off, I definitely agree we need a way to tell userspace exactly what has happened. I wanted to start a discussion about that in i-g-t patch "Unrelated hotplug uevent masking out actual test result" but it didn't get much traction. For testing purposes, it is unacceptable that userspace only gets notified that "something happened". Still, as far as I know, userspace is expected to ask for a full reprobe when something has changed, and that is apparently part of the DRM spec, so we can't expect that it could query for an update on "only the things that changed". However, one way to mitigate this is to make sure that the driver knows what changed and only updates these things when a full reprobe is requested. Is this the approach that you have in mind? The methodology behind my series follows what is currently done: detect change in whatever way necessary, inform userspace and let it trigger full reprobe. If I'm understanding correctly, what you're suggesting is instead to reprobe what is needed on the kernel side when an associated change occurs instead of having userspace trigger it, and then let userspace aware that something changed and return the "cached" updated status when userspace asks for the subsequent reprobe. Is that correct? Cheers, Paul > > > > --- > > > > drivers/gpu/drm/drm_edid.c | 45 > > > > + > > > > include/drm/drm_edid.h | 3 +++ > > > > 2 files changed, 48 insertions(+) > > > > > > > > diff --git a/drivers/gpu/drm/drm_edid.c > > > > b/drivers/gpu/drm/drm_edid.c > > > > index 6bb6337be920..f6ce8bc2907a 100644 > > > > --- a/drivers/gpu/drm/drm_edid.c > > > > +++ b/drivers/gpu/drm/drm_edid.c > > > > @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct > > > > drm_connector *connector, > > > > } > > > > return; > > > > } > > > > + > > > > +/** > > > > + * drm_check_edid_changed - Check whether the EDID changed > > > > since > > > > the last update > > > > + * @connector: connector we're probing > > > > + * @adapter: I2C adapter to use for DDC > > > > + * > > > > + * Check whether the EDID changed since the last time it was > > > > updated in the > > > > + * drm blob cache. > > > > + * > > > > + * Return: A boolean indicating whether a change happened or > > > > not. > > > > + */ > > > > +bool drm_check_edid_changed(struct drm_connector *connector, >
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, Jul 25, 2017 at 10:58:55AM +0300, Paul Kocialkowski wrote: > On Tue, 2017-07-25 at 09:34 +0200, Daniel Vetter wrote: > > On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski > > wrote: > > > On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote: > > > > On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote: > > > > > This adds a common drm helper to detect whether the EDID changed > > > > > from > > > > > the last known cached one. This is useful help detect that a > > > > > monitor > > > > > was > > > > > changed during a suspend/resume cycle. > > > > > > > > > > When that happens (a monitor is replaced by another one during > > > > > suspend), > > > > > no hotplug event will be triggered so the change will not be > > > > > caught > > > > > at > > > > > resume time. Detecting that the EDID changed allows detecting > > > > > it. > > > > > > > > > > Signed-off-by: Paul Kocialkowski > > > > com> > > > > > > > > I can't find the older mails I've typed about this, but the plan > > > > we've > > > > discussed a while back was: > > > > - Add a generational counter to each connector, maybe even expose > > > > it > > > > to > > > > userspace. > > > > > > > > - Increment that counter every time something changed, e.g. > > > > connector->status in the propbe helpers, or when attaching a new > > > > edid > > > > with the set_edid helper. > > > > > > > > - Tada, no changes needed to drivers, and easily extensible to > > > > other > > > > things than edid! > > > > > > I don't see how it solves the problem here though. After a > > > suspend/resume cycle, there is simply no indication that anything > > > has > > > changed when a monitor was replaced by another one, so I don't see > > > how > > > adding a counter in the mix would help. > > > > > > Could you provide more details about the reasoning? I feel like I'm > > > missing something here. > > > > Your bug doesn't just exist over s/r, it's just much easier to observe > > in s/r since users can take however long they want to with plugging in > > a different monitor. But the same issue exists e.g. when we go from > > hpd to polling because too much noise on the line. > > > > Wrt the suspend/resume issue: What we need to do on resume is do a > > full reprobe of all outputs, in an async worker. Telling userspace to > > do this by sending an uevent was the cheapest way, but it'd be better > > if the kernel could do that asynchronously and inform userspace about > > the exact changes. And there's more to reprobe than just the edid, and > > we don't want to re-invent a separate reprobe path just for resume > > like you start in your patch series. So yeah my plan was missing: > > > > - force a full async reprobe after resume (maybe we could reuse the > > poll worker for that as a one-shot). > > First off, I definitely agree we need a way to tell userspace exactly > what has happened. I wanted to start a discussion about that in i-g-t > patch "Unrelated hotplug uevent masking out actual test result" but it > didn't get much traction. For testing purposes, it is unacceptable that > userspace only gets notified that "something happened". > > Still, as far as I know, userspace is expected to ask for a full reprobe > when something has changed, and that is apparently part of the DRM spec, > so we can't expect that it could query for an update on "only the things > that changed". We can update that spec in a backwards compatible way. E.g. we can ask for the current properties without forcing a reprobe (won't even call down into the driver), and userspace could use that to check which connector has an incremented epoche counter since the last time it sampled things. Then it can reprobe just that one. Old userspace wouldn't know about this, and would keep working as-is. > However, one way to mitigate this is to make sure that the driver knows > what changed and only updates these things when a full reprobe is > requested. Is this the approach that you have in mind? > > The methodology behind my series follows what is currently done: detect > change in whatever way necessary, inform userspace and let it trigger > full reprobe. If I'm understanding correctly, what you're suggesting is > instead to reprobe what is needed on the kernel side when an associated > change occurs instead of having userspace trigger it, and then let > userspace aware that something changed and return the "cached" updated > status when userspace asks for the subsequent reprobe. Is that correct? There's two things: the uapi discussion and the internal implementation, imo their separate (but somewhat connected) topics. - For the internal implementation of detecting edid changes I don't like your approach of rolling a completely new detect path just for resume. I think we can very well integrate that into the existing probe code using the approach I've laid out. - There's more than just edid (e.g. hdcp status, various stuff that's handled in dp aux for DP sink
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, 2017-07-25 at 10:16 +0200, Daniel Vetter wrote: > On Tue, Jul 25, 2017 at 10:58:55AM +0300, Paul Kocialkowski wrote: > > On Tue, 2017-07-25 at 09:34 +0200, Daniel Vetter wrote: > > > On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski > > > wrote: > > > > On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote: > > > > > On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski > > > > > wrote: > > > > > > This adds a common drm helper to detect whether the EDID > > > > > > changed > > > > > > from > > > > > > the last known cached one. This is useful help detect that a > > > > > > monitor > > > > > > was > > > > > > changed during a suspend/resume cycle. > > > > > > > > > > > > When that happens (a monitor is replaced by another one > > > > > > during > > > > > > suspend), > > > > > > no hotplug event will be triggered so the change will not be > > > > > > caught > > > > > > at > > > > > > resume time. Detecting that the EDID changed allows > > > > > > detecting > > > > > > it. > > > > > > > > > > > > Signed-off-by: Paul Kocialkowski > > > > > tel. > > > > > > com> > > > > > > > > > > I can't find the older mails I've typed about this, but the > > > > > plan > > > > > we've > > > > > discussed a while back was: > > > > > - Add a generational counter to each connector, maybe even > > > > > expose > > > > > it > > > > > to > > > > > userspace. > > > > > > > > > > - Increment that counter every time something changed, e.g. > > > > > connector->status in the propbe helpers, or when attaching a > > > > > new > > > > > edid > > > > > with the set_edid helper. > > > > > > > > > > - Tada, no changes needed to drivers, and easily extensible to > > > > > other > > > > > things than edid! > > > > > > > > I don't see how it solves the problem here though. After a > > > > suspend/resume cycle, there is simply no indication that > > > > anything > > > > has > > > > changed when a monitor was replaced by another one, so I don't > > > > see > > > > how > > > > adding a counter in the mix would help. > > > > > > > > Could you provide more details about the reasoning? I feel like > > > > I'm > > > > missing something here. > > > > > > Your bug doesn't just exist over s/r, it's just much easier to > > > observe > > > in s/r since users can take however long they want to with > > > plugging in > > > a different monitor. But the same issue exists e.g. when we go > > > from > > > hpd to polling because too much noise on the line. > > > > > > Wrt the suspend/resume issue: What we need to do on resume is do a > > > full reprobe of all outputs, in an async worker. Telling userspace > > > to > > > do this by sending an uevent was the cheapest way, but it'd be > > > better > > > if the kernel could do that asynchronously and inform userspace > > > about > > > the exact changes. And there's more to reprobe than just the edid, > > > and > > > we don't want to re-invent a separate reprobe path just for resume > > > like you start in your patch series. So yeah my plan was missing: > > > > > > - force a full async reprobe after resume (maybe we could reuse > > > the > > > poll worker for that as a one-shot). > > > > First off, I definitely agree we need a way to tell userspace > > exactly > > what has happened. I wanted to start a discussion about that in i-g- > > t > > patch "Unrelated hotplug uevent masking out actual test result" but > > it > > didn't get much traction. For testing purposes, it is unacceptable > > that > > userspace only gets notified that "something happened". > > > > Still, as far as I know, userspace is expected to ask for a full > > reprobe > > when something has changed, and that is apparently part of the DRM > > spec, > > so we can't expect that it could query for an update on "only the > > things > > that changed". > > We can update that spec in a backwards compatible way. E.g. we can ask > for > the current properties without forcing a reprobe (won't even call down > into the driver), and userspace could use that to check which > connector > has an incremented epoche counter since the last time it sampled > things. > Then it can reprobe just that one. > > Old userspace wouldn't know about this, and would keep working as-is. So the level of detail you're aiming at providing userspace is "connector foo changed" then? I agree it is better than the current "some connector(s) changed", but what I'd like to see for proper testing is a way to find out "bar for connector foo changed". > > However, one way to mitigate this is to make sure that the driver > > knows > > what changed and only updates these things when a full reprobe is > > requested. Is this the approach that you have in mind? > > > > The methodology behind my series follows what is currently done: > > detect > > change in whatever way necessary, inform userspace and let it > > trigger > > full reprobe. If I'm understanding correctly, what you're suggesting > > is > > instead to reprobe what is needed on the kernel side
Re: [PATCH 1/2] drm/edid: Add helper to detect whether EDID changed
On Tue, Jul 25, 2017 at 03:18:04PM +0300, Paul Kocialkowski wrote: > On Tue, 2017-07-25 at 10:16 +0200, Daniel Vetter wrote: > > On Tue, Jul 25, 2017 at 10:58:55AM +0300, Paul Kocialkowski wrote: > > > On Tue, 2017-07-25 at 09:34 +0200, Daniel Vetter wrote: > > > > On Tue, Jul 25, 2017 at 9:25 AM, Paul Kocialkowski > > > > wrote: > > > > > On Tue, 2017-07-25 at 08:53 +0200, Daniel Vetter wrote: > > > > > > On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski > > > > > > wrote: > > > > > > > This adds a common drm helper to detect whether the EDID > > > > > > > changed > > > > > > > from > > > > > > > the last known cached one. This is useful help detect that a > > > > > > > monitor > > > > > > > was > > > > > > > changed during a suspend/resume cycle. > > > > > > > > > > > > > > When that happens (a monitor is replaced by another one > > > > > > > during > > > > > > > suspend), > > > > > > > no hotplug event will be triggered so the change will not be > > > > > > > caught > > > > > > > at > > > > > > > resume time. Detecting that the EDID changed allows > > > > > > > detecting > > > > > > > it. > > > > > > > > > > > > > > Signed-off-by: Paul Kocialkowski > > > > > > tel. > > > > > > > com> > > > > > > > > > > > > I can't find the older mails I've typed about this, but the > > > > > > plan > > > > > > we've > > > > > > discussed a while back was: > > > > > > - Add a generational counter to each connector, maybe even > > > > > > expose > > > > > > it > > > > > > to > > > > > > userspace. > > > > > > > > > > > > - Increment that counter every time something changed, e.g. > > > > > > connector->status in the propbe helpers, or when attaching a > > > > > > new > > > > > > edid > > > > > > with the set_edid helper. > > > > > > > > > > > > - Tada, no changes needed to drivers, and easily extensible to > > > > > > other > > > > > > things than edid! > > > > > > > > > > I don't see how it solves the problem here though. After a > > > > > suspend/resume cycle, there is simply no indication that > > > > > anything > > > > > has > > > > > changed when a monitor was replaced by another one, so I don't > > > > > see > > > > > how > > > > > adding a counter in the mix would help. > > > > > > > > > > Could you provide more details about the reasoning? I feel like > > > > > I'm > > > > > missing something here. > > > > > > > > Your bug doesn't just exist over s/r, it's just much easier to > > > > observe > > > > in s/r since users can take however long they want to with > > > > plugging in > > > > a different monitor. But the same issue exists e.g. when we go > > > > from > > > > hpd to polling because too much noise on the line. > > > > > > > > Wrt the suspend/resume issue: What we need to do on resume is do a > > > > full reprobe of all outputs, in an async worker. Telling userspace > > > > to > > > > do this by sending an uevent was the cheapest way, but it'd be > > > > better > > > > if the kernel could do that asynchronously and inform userspace > > > > about > > > > the exact changes. And there's more to reprobe than just the edid, > > > > and > > > > we don't want to re-invent a separate reprobe path just for resume > > > > like you start in your patch series. So yeah my plan was missing: > > > > > > > > - force a full async reprobe after resume (maybe we could reuse > > > > the > > > > poll worker for that as a one-shot). > > > > > > First off, I definitely agree we need a way to tell userspace > > > exactly > > > what has happened. I wanted to start a discussion about that in i-g- > > > t > > > patch "Unrelated hotplug uevent masking out actual test result" but > > > it > > > didn't get much traction. For testing purposes, it is unacceptable > > > that > > > userspace only gets notified that "something happened". > > > > > > Still, as far as I know, userspace is expected to ask for a full > > > reprobe > > > when something has changed, and that is apparently part of the DRM > > > spec, > > > so we can't expect that it could query for an update on "only the > > > things > > > that changed". > > > > We can update that spec in a backwards compatible way. E.g. we can ask > > for > > the current properties without forcing a reprobe (won't even call down > > into the driver), and userspace could use that to check which > > connector > > has an incremented epoche counter since the last time it sampled > > things. > > Then it can reprobe just that one. > > > > Old userspace wouldn't know about this, and would keep working as-is. > > So the level of detail you're aiming at providing userspace is > "connector foo changed" then? I agree it is better than the current > "some connector(s) changed", but what I'd like to see for proper testing > is a way to find out "bar for connector foo changed". If you want taht level of detail you need introspection in a in-kernel selftest I think. We'd need to rather massively change/extend the uapi to support that level of testing through the uapi, and thus
