Em Mon, 16 Apr 2018 21:48:56 +0200
Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> On 04/16/2018 09:40 PM, Mauro Carvalho Chehab wrote:
> > Em Mon, 16 Apr 2018 21:27:01 +0200
> > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> >
> >> On 04/16/2018 08:01 PM, Mauro Carvalho Chehab wrote:
> >>> Em Mon, 16 Apr 2018 15:21:16 +0200
> >>> Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> >>>
> >>>> From: Hans Verkuil <hansverk@xxxxxxxxx>
> >>>>
> >>>> This adds support for 'proper' functions to the existing API.
> >>>> This information was before only available through the new v2
> >>>> API, with this change it's available to both.
> >>>>
> >>>> Yes, the plan is to allow entities to expose multiple functions for
> >>>> multi-function devices, but we do not support it anywhere so this
> >>>> is still vaporware.
> >>>
> >>> I'm not convinced about that. I would, instead, just keep it as-is
> >>> and be sure that applications stop use the legacy calls.
> >>
> >> You can't. First of all, since the new API does not provide the pad index
> >> (fixed in patch 6/9) it is impossible to use the new API with any driver
> >> that supports SETUP_LINK.
> >
> > Yeah, unfortunately, the properties API was just an empty promise.
> >
> > Anyway, as you said, patch 6/9 solves it.
> >
> >> So any such driver that uses any of the newer
> >> subdevs with a function that is mapped to MEDIA_ENT_T_DEVNODE_UNKNOWN
> >> is currently not reporting that correctly. A good example is the
> >> imx driver. But also others if they are combined with such newer subdevs.
> >
> > As far as I remember, other drivers also return MEDIA_ENT_F_UNKNOWN
> > (with also maps to MEDIA_ENT_T_DEVNODE_UNKNOWN) even via the new API,
> > as the developer never cared to fill the entity function, even
> > producing warnings.
> >
> >> There is nothing wrong with the old API, except for not reporting the
> >> proper function value in field 'type' due to historical concerns.
> >
> > There is. That's why we took about one year developing a new API.
>
> If you don't need the new functionality (like interfaces), then it is
> perfectly fine. It's been in use for many years now.
>
> >
> >> There is NO WAY we can suddenly prohibit applications from using the old
> >> API since the new API was never usable. And besides that, we have no method
> >> of knowing who uses the old API since such applications are likely custom
> >> for specific hardware.
> >
> > Nobody is forbidding anything. We're just freezing it, as its
> > functionality was superseded.
> >
> >> All that is really missing in the 'old' API (I hate the terms 'old' and
> >> 'new', they are misleading) is a proper 'function' field. Let's just add it
> >> and make it consistent with the documentation about entity functions.
> >
> > It misses interfaces - with is needed to identify what interface controls
> > what.
>
> Sure, but for most use cases interfaces are not needed. But reporting the correct
> function is very useful, makes the API consistent with the documentation (which
> only talks about functions and no longer refers to types) and the new API and it
> is trivial to add.
>
> I'm not advocating any further chances, but while writing the compliance tests
> for this it was incredibly ugly to have this mismatch between 'type' and 'function'.
I'm not a big fan of this patch. IMHO, we should really try to
not touch APIs that are replaced by a newer version, but let's
hear for other opinions about this particular change.
>
> The function of an entity is a critical piece of information, and having it
> clamped to UNKNOWN for the newer functions is just wrong.
As I said before, just the changes on this patchset won't solve it, as
several drivers simply don't initialize the subdev type/function.
> Regards,
>
> Hans
>
> >
> >>
> >>>
> >>>>
> >>>> Signed-off-by: Hans Verkuil <hansverk@xxxxxxxxx>
> >>>> ---
> >>>> drivers/media/media-device.c | 1 +
> >>>> include/uapi/linux/media.h | 7 ++++++-
> >>>> 2 files changed, 7 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> >>>> index 7c3ab37c258a..dca1e5a3e0f9 100644
> >>>> --- a/drivers/media/media-device.c
> >>>> +++ b/drivers/media/media-device.c
> >>>> @@ -115,6 +115,7 @@ static long media_device_enum_entities(struct media_device *mdev,
> >>>> if (ent->name)
> >>>> strlcpy(entd->name, ent->name, sizeof(entd->name));
> >>>> entd->type = ent->function;
> >>>> + entd->function = ent->function;
> >>>> entd->revision = 0; /* Unused */
> >>>
> >>> I got confused here, until I went to the code and noticed that
> >>> entd->type is actually touched after this.
> >>>
> >>> If we're willing to do that, you should add a comment there explaining
> >>> why we need to pass both type and function to userspace.
> >>
> >> True.
> >>
> >> Regards,
> >>
> >> Hans
> >>
> >>>
> >>>> entd->flags = ent->flags;
> >>>> entd->group_id = 0; /* Unused */
> >>>> diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
> >>>> index 86c7dcc9cba3..ac08acffdb65 100644
> >>>> --- a/include/uapi/linux/media.h
> >>>> +++ b/include/uapi/linux/media.h
> >>>> @@ -146,6 +146,10 @@ struct media_device_info {
> >>>> /* OR with the entity id value to find the next entity */
> >>>> #define MEDIA_ENT_ID_FLAG_NEXT (1 << 31)
> >>>>
> >>>> +/* Appeared in 4.18.0 */
> >>>> +#define MEDIA_ENTITY_DESC_HAS_FUNCTION(media_version) \
> >>>> + ((media_version) >= 0x00041200)
> >>>> +
> >>>> struct media_entity_desc {
> >>>> __u32 id;
> >>>> char name[32];
> >>>> @@ -155,8 +159,9 @@ struct media_entity_desc {
> >>>> __u32 group_id;
> >>>> __u16 pads;
> >>>> __u16 links;
> >>>> + __u32 function;
> >>>>
> >>>> - __u32 reserved[4];
> >>>> + __u32 reserved[3];
> >>>>
> >>>> union {
> >>>> /* Node specifications */
> >>>
> >>>
> >>>
> >>> Thanks,
> >>> Mauro
> >>>
> >>
> >
> >
> >
> > Thanks,
> > Mauro
> >
>
Thanks,
Mauro
