On Fri, Mar 07, 2025 at 06:34:42AM +0200, Dmitry Baryshkov wrote: > 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 <dmitry.baryshkov@xxxxxxxxxx> Just wanted to drop my "I like this" on your series here. Short read/writes come from unix pipes, and they're everywhere, and yes ime everyone gets them wrong. So ack or whatever that means :-) -Sima > --- > 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@xxxxxxxxxx > > 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@xxxxxxxxxx > > --- > Dmitry Baryshkov (7): > 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-aux-dev: 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_aux_dev.c | 12 +- > 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 +++++- > 12 files changed, 322 insertions(+), 315 deletions(-) > --- > base-commit: 565351ae7e0cee80e9b5ed84452a5b13644ffc4d > change-id: 20241231-drm-rework-dpcd-access-b0fc2e47d613 > > Best regards, > -- > Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > -- Simona Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
