Re: [PATCH v2 6/8] drm: Introduce drm_bridge_mode_valid()
From: Archit Taneja
Date: Mon May 15 2017 - 00:19:14 EST
On 05/12/2017 04:31 PM, Laurent Pinchart wrote:
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.
I guess converting into list would be a good start to achieve this. We'd probably
need to extend/redo the drm_bridge_attach() API to tweak the order in the which
the ops are called.
Thanks,
Archit
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project