Hi Archit,
On Friday 12 May 2017 16:20:07 Archit Taneja wrote:
> On 05/12/2017 03:08 PM, Laurent Pinchart wrote:
> > On Wednesday 10 May 2017 17:14:33 Daniel Vetter wrote:
> >> On Wed, May 10, 2017 at 04:41:09PM +0300, Ville Syrjälä wrote:
> >>> On Tue, May 09, 2017 at 06:00:13PM +0100, Jose Abreu wrote:
> >>>> Introduce a new helper function which calls mode_valid() callback
> >>>> for all bridges in an encoder chain.
> >>>>
> >>>> Signed-off-by: Jose Abreu <joabreu@xxxxxxxxxxxx>
> >>>> Cc: Carlos Palminha <palminha@xxxxxxxxxxxx>
> >>>> Cc: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> >>>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >>>> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> >>>> Cc: Dave Airlie <airlied@xxxxxxxx>
> >>>> Cc: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> >>>> Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
> >>>> ---
> >>>>
> >>>> drivers/gpu/drm/drm_bridge.c | 33 +++++++++++++++++++++++++++++++++
> >>>> include/drm/drm_bridge.h | 2 ++
> >>>> 2 files changed, 35 insertions(+)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/drm_bridge.c
> >>>> b/drivers/gpu/drm/drm_bridge.c
> >>>> index 86a7637..dc8cdfe 100644
> >>>> --- a/drivers/gpu/drm/drm_bridge.c
> >>>> +++ b/drivers/gpu/drm/drm_bridge.c
> >>>> @@ -206,6 +206,39 @@ bool drm_bridge_mode_fixup(struct drm_bridge
> >>>> *bridge,
> >>>>
> >>>> EXPORT_SYMBOL(drm_bridge_mode_fixup);
> >>>>
> >>>> /**
> >>>>
> >>>> + * drm_bridge_mode_valid - validate the mode against all bridges in
> >>>> the
> >>>> + * encoder chain.
> >>>> + * @bridge: bridge control structure
> >>>> + * @mode: desired mode to be validated
> >>>> + *
> >>>> + * Calls &drm_bridge_funcs.mode_valid for all the bridges in the
> >>>> encoder
> >>>> + * chain, starting from the first bridge to the last. If at least one
> >>>> bridge + * does not accept the mode the function returns the error
> >>>> code.
> >>>> + *
> >>>> + * Note: the bridge passed should be the one closest to the encoder.
> >>>> + *
> >>>> + * RETURNS:
> >>>> + * MODE_OK on success, drm_mode_status Enum error code on failure
> >>>> + */
> >>>> +enum drm_mode_status drm_bridge_mode_valid(struct drm_bridge *bridge,
> >>>> + const struct
drm_display_mode
> >
> > *mode)
> >
> >>>> +{
> >>>> + enum drm_mode_status ret = MODE_OK;
> >>>> +
> >>>> + if (!bridge)
> >>>> + return ret;
> >>>> +
> >>>> + if (bridge->funcs->mode_valid)
> >>>> + ret = bridge->funcs->mode_valid(bridge, mode);
> >>>> +
> >>>> + if (ret != MODE_OK)
> >>>> + return ret;
> >>>> +
> >>>> + return drm_bridge_mode_valid(bridge->next, mode);
> >>>
> >>> Looks like it should be pretty trivial to avoid the recursion.
> >>>
> >>> Am I correct in interpreting this that bridges have some kind of
> >>> a hand rolled linked list implementation? Reusing the standard
> >>> linked lists would allow you to use list_for_each() etc.
> >>
> >> Yeah it's a hand-rolled list, but current hw also has a bridge nesting
> >> depth of 2, so it really doesn't matter. I guess once we have real long
> >> chains of bridges we can fix this (and just using list_head sounds like a
> >> great idea).
> >
> > Even if not really needed right now, it's a pretty easy cleanup, if Jose
> > has time to handle it in v3 of this series let's not postpone it ;-)
>
> jfyi, some of the bridge functions call the ops from the last bridge in the
> chain to first, so we'd need to use list_for_each_entry_prev() (or something
> like that) for them.
And now that I think about it, for some of the operations (especially
enable/disable) I believe that the bridge should be able to decide whether to
call the next/previous bridge first or to configure its hardware first. I can
image bridges that need the previous bridge in the chain to provide a valid
clock before they get started, as well as bridges that need to be started with
the incoming video signal stopped.
--
Regards,
Laurent Pinchart
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