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[2001:14ba:a0c3:3a00:264b:feff:fe8b:be8a]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-549ba88332dsm416136e87.181.2025.03.13.22.59.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Mar 2025 22:59:55 -0700 (PDT) From: Dmitry Baryshkov Subject: [PATCH RFC v4 0/6] drm/display: dp: add new DPCD access functions Date: Fri, 14 Mar 2025 07:59:41 +0200 Message-Id: <20250314-drm-rework-dpcd-access-v4-0-e86ef6fc6d76@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAM3F02cC/3XOwYoCMQwG4FeRnq2kaZ1RTwsLPsBexUNNM1p2n UoqXUXm3S1zcReZ45+QL/9DZZbIWW1mDyVcYo6pr8HNZ4pOvj+yjqFmhYDOoDU6yFkL/yb51uF CQXsizlkfoCNk14bGWFWPL8JdvI3wTn1tP9W+Dk8xX5Pcx2fFjKvqLsGYdsotRoNuOwIEBhcO9 PETey9pkeQ4mgVfjoXJfgWr48IaG8COWgpvjv3rTPex1VmDc976VbNi/ucMw/AEKA0RTlIBAAA = X-Change-ID: 20241231-drm-rework-dpcd-access-b0fc2e47d613 To: Lyude Paul , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , Jani Nikula , Alex Deucher , =?utf-8?q?Christian_K=C3=B6nig?= , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Xinliang Liu , Tian Tao , Xinwei Kong , Sumit Semwal , Yongqin Liu , John Stultz Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Dmitry Baryshkov , Jani Nikula X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2996; i=dmitry.baryshkov@oss.qualcomm.com; h=from:subject:message-id; bh=66iKtCroS+wUxpRA2gMU25wN8Ri0QuCTAm5ya+VinMY=; b=owEBbQGS/pANAwAKAYs8ij4CKSjVAcsmYgBn08XYVO0V/YkMxV3viOt7WsQ1/uAO3FubeT9rT 25+Usjws1WJATMEAAEKAB0WIQRMcISVXLJjVvC4lX+LPIo+Aiko1QUCZ9PF2AAKCRCLPIo+Aiko 1QX9B/4wtWeCg/oTKStVqTVja2e5IG4wSPWhflap5NVulnj7g33BPZluzpa3pS60cHgsMfT8nFP KjjG9BSCYbTn8Sf0+H/AKWvm5DxqWCcOQX4Jcra9OnvX2ejrd+WqFzeYdEXkYrNdbrKB5zolt7P drafp15b8urG28Vsg/LsY8XPIktMvgr96DyMsM0qRZs04F/yl1E69JjnQt1W+/cjUwHwUHrWe2T XzYnidkAX9HjM0idwYWw6zS+Hal8QCvq/tMzK3m9BOt52T0P7D8UTaoEh165zjpkJFmHQezND9b 5ZyUSzPUrKk1Yrt7HNF3+tJInPHHefFFCeyHyCqw3SRV1l1O X-Developer-Key: i=dmitry.baryshkov@oss.qualcomm.com; a=openpgp; fpr=8F88381DD5C873E4AE487DA5199BF1243632046A X-Authority-Analysis: v=2.4 cv=a5Iw9VSF c=1 sm=1 tr=0 ts=67d3c5df cx=c_pps a=EVbN6Ke/fEF3bsl7X48z0g==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=Vs1iUdzkB0EA:10 a=VwQbUJbxAAAA:8 a=KKAkSRfTAAAA:8 a=EUspDBNiAAAA:8 a=BDmTPyut6bhdKis1t5QA:9 a=QEXdDO2ut3YA:10 a=a_PwQJl-kcHnX1M80qC6:22 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-GUID: DGJNKeuZ9AYsgwMJp6w5jWf7if_j3NdW X-Proofpoint-ORIG-GUID: DGJNKeuZ9AYsgwMJp6w5jWf7if_j3NdW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-14_02,2025-03-13_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 suspectscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 clxscore=1015 spamscore=0 mlxscore=0 adultscore=0 malwarescore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2503140045 Existing DPCD access functions return an error code or the number of bytes being read / write in case of partial access. However a lot of drivers either (incorrectly) ignore partial access or mishandle error codes. In other cases this results in a boilerplate code which compares returned value with the size. As suggested by Jani implement new set of DPCD access helpers, which ignore partial access, always return 0 or an error code. Implement new helpers using existing functions to ensure backwards compatibility and to assess necessity to handle incomplete reads on a global scale. Currently only one possible place has been identified, dp-aux-dev, which needs to handle possible holes in DPCD. This series targets only the DRM helpers code. If the approach is found to be acceptable, each of the drivers should be converted on its own. Signed-off-by: Dmitry Baryshkov --- Changes in v4: - Actually dropped the dp-aux-dev patch (Lyude). - Added two missing full stops in linuxdoc (Lyude). - Link to v3: https://lore.kernel.org/r/20250307-drm-rework-dpcd-access-v3-0-9044a3a868ee@linaro.org Changes in v3: - Fixed cover letter (Jani) - Added intel-gfx and intel-xe to get the series CI-tested (Jani) - Link to v2: https://lore.kernel.org/r/20250301-drm-rework-dpcd-access-v2-0-4d92602fc7cd@linaro.org Changes in v2: - Reimplemented new helpers using old ones (Lyude) - Reworked the drm_dp_dpcd_read_link_status() patch (Lyude) - Dropped the dp-aux-dev patch (Jani) - Link to v1: https://lore.kernel.org/r/20250117-drm-rework-dpcd-access-v1-0-7fc020e04dbc@linaro.org --- Dmitry Baryshkov (6): drm/display: dp: implement new access helpers drm/display: dp: change drm_dp_dpcd_read_link_status() return value drm/display: dp: use new DCPD access helpers drm/display: dp-cec: use new DCPD access helpers drm/display: dp-mst-topology: use new DCPD access helpers drm/display: dp-tunnel: use new DCPD access helpers drivers/gpu/drm/amd/amdgpu/atombios_dp.c | 8 +- .../gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 2 +- drivers/gpu/drm/display/drm_dp_cec.c | 37 ++- drivers/gpu/drm/display/drm_dp_helper.c | 307 +++++++++------------ drivers/gpu/drm/display/drm_dp_mst_topology.c | 105 ++++--- drivers/gpu/drm/display/drm_dp_tunnel.c | 20 +- drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c | 4 +- drivers/gpu/drm/msm/dp/dp_ctrl.c | 24 +- drivers/gpu/drm/msm/dp/dp_link.c | 18 +- drivers/gpu/drm/radeon/atombios_dp.c | 8 +- include/drm/display/drm_dp_helper.h | 92 +++++- 11 files changed, 317 insertions(+), 308 deletions(-) --- base-commit: b0894e40afe2bd05d1fda68cc364665ac2b00e09 change-id: 20241231-drm-rework-dpcd-access-b0fc2e47d613 Best regards, -- Dmitry Baryshkov