Re: [PATCH v2 6/8] drm: Introduce drm_bridge_mode_valid()

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On 05/12/2017 03:08 PM, Laurent Pinchart wrote:
Hi Daniel,

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.

Archit

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