Hi Andrzej.
After reading through the series a few more comments.
1) The subject of this patch could be improved.
Consider something like:
drm: add ddc link in sysfs created by drm_connector
This spells out much better what the patch achieve.
2) The purpsoe of drm_connector.ddc is to provide drm_connector with
info to create the symlink.
Yet in many follow-up patches the drivers are changed so
drm_connector.ddc is their only reference to struct i2c_adapter.
But the ownership is not clear here.
Who owns the reference to i2c_adapter - and who has the
responsibility to call put() on the adapter.
Looking at the conversions done then some drivers are converted
so they only use drm_connector.ddc, and other drivers have their own
reference to i2c_adapter.
The latter looks like the correct solution as the ownership of the
reference belongs to the driver and not drm_connector.
In other words - a conversion where the drivers only assigned
drm_connector.ddc (using drm_connector_init_with_ddc()),
seems like a more clean design that does not mix up ownership.
This is at least how I see it.
I did not take this type of look at the patches before. Sorry
for providing feedback this late.
Sam
On Fri, Jul 26, 2019 at 08:37:59AM +0200, Sam Ravnborg wrote:
> Hi Andrzej.
>
> Patch looks good, but one kernel-doc detail.
>
> On Wed, Jul 24, 2019 at 03:59:23PM +0200, Andrzej Pietrasiewicz wrote:
> > Add generic code which creates symbolic links in sysfs, pointing to ddc
> > interface used by a particular video output. For example:
> >
> > ls -l /sys/class/drm/card0-HDMI-A-1/ddc
> > lrwxrwxrwx 1 root root 0 Jun 24 10:42 /sys/class/drm/card0-HDMI-A-1/ddc \
> > -> ../../../../soc/13880000.i2c/i2c-2
> >
> > This makes it easy for user to associate a display with its ddc adapter
> > and use e.g. ddcutil to control the chosen monitor.
> >
> > This patch adds an i2c_adapter pointer to struct drm_connector. Particular
> > drivers can then use it instead of using their own private instance. If a
> > connector contains a ddc, then create a symbolic link in sysfs.
> >
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
> > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_sysfs.c | 8 ++++++++
> > include/drm/drm_connector.h | 11 +++++++++++
> > 2 files changed, 19 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> > index ad10810bc972..e962a9d45f7e 100644
> > --- a/drivers/gpu/drm/drm_sysfs.c
> > +++ b/drivers/gpu/drm/drm_sysfs.c
> > @@ -14,6 +14,7 @@
> > #include <linux/err.h>
> > #include <linux/export.h>
> > #include <linux/gfp.h>
> > +#include <linux/i2c.h>
> > #include <linux/kdev_t.h>
> > #include <linux/slab.h>
> >
> > @@ -294,6 +295,9 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
> > /* Let userspace know we have a new connector */
> > drm_sysfs_hotplug_event(dev);
> >
> > + if (connector->ddc)
> > + return sysfs_create_link(&connector->kdev->kobj,
> > + &connector->ddc->dev.kobj, "ddc");
> > return 0;
> > }
> >
> > @@ -301,6 +305,10 @@ void drm_sysfs_connector_remove(struct drm_connector *connector)
> > {
> > if (!connector->kdev)
> > return;
> > +
> > + if (connector->ddc)
> > + sysfs_remove_link(&connector->kdev->kobj, "ddc");
> > +
> > DRM_DEBUG("removing \"%s\" from sysfs\n",
> > connector->name);
> >
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 4c30d751487a..33a6fff85fdb 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -41,6 +41,7 @@ struct drm_property;
> > struct drm_property_blob;
> > struct drm_printer;
> > struct edid;
> > +struct i2c_adapter;
> >
> > enum drm_connector_force {
> > DRM_FORCE_UNSPECIFIED,
> > @@ -1311,6 +1312,16 @@ struct drm_connector {
> > * [0]: progressive, [1]: interlaced
> > */
> > int audio_latency[2];
> > +
> > + /**
> > + * @ddc: associated ddc adapter.
> > + * A connector usually has its associated ddc adapter. If a driver uses
> > + * this field, then an appropriate symbolic link is created in connector
> > + * sysfs directory to make it easy for the user to tell which i2c
> > + * adapter is for a particular display.
> > + */
> > + struct i2c_adapter *ddc;
>
> To help the reader could you add in the above a reference to
> drm_connector_init_with_ddc() sp the reader is told how to init this
> field.
>
> Either add it in PATCH 2 - or merge patch 1 and 2.
>
> Sam
>
> > +
> > /**
> > * @null_edid_counter: track sinks that give us all zeros for the EDID.
> > * Needed to workaround some HW bugs where we get all 0s
> > --
> > 2.17.1
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