linux-kernel - [RFC PATCH 10/10] drm/panel: Update TODO list item for cleaning up prepared/enabled tracking

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Message-ID: <20230804140605.RFC.10.I104cdece7324b0c365e552a17f9883414ffaea01@changeid>
Date:   Fri,  4 Aug 2023 14:06:13 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 10/10] drm/panel: Update TODO list item for cleaning up prepared/enabled tracking

Now that most panels have been updated not to track/double-check their
prepared/enabled state update the TODO with next steps.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 Documentation/gpu/todo.rst | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 139980487ccf..c73d9dbebbf4 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -460,26 +460,19 @@ Contact: Thomas Zimmermann <tzimmermann@...e.de>
 
 Level: Starter
 
-Clean up checks for already prepared/enabled in panels
-------------------------------------------------------
-
-In a whole pile of panel drivers, we have code to make the
-prepare/unprepare/enable/disable callbacks behave as no-ops if they've already
-been called. To get some idea of the duplicated code, try::
-
-  git grep 'if.*>prepared' -- drivers/gpu/drm/panel
-  git grep 'if.*>enabled' -- drivers/gpu/drm/panel
-
-In the patch ("drm/panel: Check for already prepared/enabled in drm_panel")
-we've moved this check to the core. Now we can most definitely remove the
-check from the individual panels and save a pile of code.
-
-In adition to removing the check from the individual panels, it is believed
-that even the core shouldn't need this check and that should be considered
-an error if other code ever relies on this check. The check in the core
-currently prints a warning whenever something is relying on this check with
-dev_warn(). After a little while, we likely want to promote this to a
-WARN(1) to help encourage folks not to rely on this behavior.
+Never double prepare/enable/disable/unprepare a panel
+-----------------------------------------------------
+
+As of commit d2aacaf07395 ("drm/panel: Check for already prepared/enabled in
+drm_panel"), we have a check in the drm_panel core to make sure nobody
+double-calls prepare/enable/disable/unprepare. However, that extra double-check
+shouldn't be necessary. The caller should always be matching up calls of
+prepare/unprepare and matching up calls of enable/disable.
+
+Hopefully the warning printed will encourage everyone to fix this. Eventually
+we'll likely want to change this to a WARN_ON and (perhaps) fully remove the
+check. NOTE: even if we remove the double-check, drm_panel core still needs
+to track the enabled/prepared state for its own purposes.
 
 Contact: Douglas Anderson <dianders@...omium.org>
 
-- 
2.41.0.585.gd2178a4bd4-goog