linux-kernel - [PATCH v4 05/23] drm/connector: hdmi: Factor out bpc and format computation logic

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Message-Id: <20250425-hdmi-conn-yuv-v4-5-5e55e2aaa3fa@collabora.com>
Date: Fri, 25 Apr 2025 13:26:56 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Dave Stevenson <dave.stevenson@...pberrypi.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
 Dmitry Baryshkov <lumag@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v4 05/23] drm/connector: hdmi: Factor out bpc and format
 computation logic

In preparation to support fallback to an alternative output format, e.g.
YUV420, when RGB cannot be used for any of the available color depths,
move the bpc try loop out of hdmi_compute_config() and, instead, make it
part of hdmi_compute_format(), while adding a new parameter to the
latter holding the output format to be checked and eventually set.

Since this helper now also changes hdmi.output_bpc in addition to
hdmi.output_format, highlight the extended functionality by renaming it
to hdmi_compute_format_bpc().

This improves code reusability and further extensibility, without
introducing any functional changes.

Reviewed-by: Maxime Ripard <mripard@...nel.org>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
---
 drivers/gpu/drm/display/drm_hdmi_state_helper.c | 60 ++++++++++++-------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index f54eb5c594cddbd67dfacb5e06d54e9ce7851013..9e0a468073acbb2477eff1abef1c09d63620afaa 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -605,45 +605,22 @@ hdmi_try_format_bpc(const struct drm_connector *connector,
 }
 
 static int
-hdmi_compute_format(const struct drm_connector *connector,
-		    struct drm_connector_state *conn_state,
-		    const struct drm_display_mode *mode,
-		    unsigned int bpc)
-{
-	struct drm_device *dev = connector->dev;
-
-	/*
-	 * TODO: Add support for YCbCr420 output for HDMI 2.0 capable
-	 * devices, for modes that only support YCbCr420.
-	 */
-	if (hdmi_try_format_bpc(connector, conn_state, mode, bpc, HDMI_COLORSPACE_RGB)) {
-		conn_state->hdmi.output_format = HDMI_COLORSPACE_RGB;
-		return 0;
-	}
-
-	drm_dbg_kms(dev, "Failed. No Format Supported for that bpc count.\n");
-
-	return -EINVAL;
-}
-
-static int
-hdmi_compute_config(const struct drm_connector *connector,
-		    struct drm_connector_state *conn_state,
-		    const struct drm_display_mode *mode)
+hdmi_compute_format_bpc(const struct drm_connector *connector,
+			struct drm_connector_state *conn_state,
+			const struct drm_display_mode *mode,
+			unsigned int max_bpc, enum hdmi_colorspace fmt)
 {
 	struct drm_device *dev = connector->dev;
-	unsigned int max_bpc = clamp_t(unsigned int,
-				       conn_state->max_bpc,
-				       8, connector->max_bpc);
 	unsigned int bpc;
 	int ret;
 
 	for (bpc = max_bpc; bpc >= 8; bpc -= 2) {
-		ret = hdmi_compute_format(connector, conn_state, mode, bpc);
-		if (ret)
+		ret = hdmi_try_format_bpc(connector, conn_state, mode, bpc, fmt);
+		if (!ret)
 			continue;
 
 		conn_state->hdmi.output_bpc = bpc;
+		conn_state->hdmi.output_format = fmt;
 
 		drm_dbg_kms(dev,
 			    "Mode %ux%u @ %uHz: Found configuration: bpc: %u, fmt: %s, clock: %llu\n",
@@ -655,9 +632,32 @@ hdmi_compute_config(const struct drm_connector *connector,
 		return 0;
 	}
 
+	drm_dbg_kms(dev, "Failed. %s output format not supported for any bpc count.\n",
+		    drm_hdmi_connector_get_output_format_name(fmt));
+
 	return -EINVAL;
 }
 
+static int
+hdmi_compute_config(const struct drm_connector *connector,
+		    struct drm_connector_state *conn_state,
+		    const struct drm_display_mode *mode)
+{
+	unsigned int max_bpc = clamp_t(unsigned int,
+				       conn_state->max_bpc,
+				       8, connector->max_bpc);
+	int ret;
+
+	/*
+	 * TODO: Add support for YCbCr420 output for HDMI 2.0 capable
+	 * devices, for modes that only support YCbCr420.
+	 */
+	ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
+				      HDMI_COLORSPACE_RGB);
+
+	return ret;
+}
+
 static int hdmi_generate_avi_infoframe(const struct drm_connector *connector,
 				       struct drm_connector_state *conn_state)
 {

-- 
2.49.0