From 663ab2ee8efe390f57effca358632566f8c26253 Mon Sep 17 00:00:00 2001 From: Milan Zamazal Date: Fri, 30 May 2025 11:08:15 +0200 Subject: apps: cam: Skip non-display GPUs Device::openCard() in the cam DRM helpers looks for a /dev/dri/card* device that can be opened and that doesn't fail when asked about DRM_CAP_DUMB_BUFFER capability (regardless whether the capability is supported by the device). There can be matching devices that are not display devices. This can lead to selection of such a device and inability to use KMS output with the `cam' application. The ultimate goal is to display something on the device and later the KMS sink will fail if there is no connector attached to the device (although it can actually fail earlier, when trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not supported). Let's avoid selecting devices without connectors, CRTCs or encoders. The added check makes the original check for DRM_CAP_DUMB_BUFFER API most likely unnecessary, let's remove it. Signed-off-by: Milan Zamazal Reviewed-by: Kieran Bingham Reviewed-by: Mattijs Korpershoek Reviewed-by: Laurent Pinchart Signed-off-by: Laurent Pinchart --- src/apps/cam/drm.cpp | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) (limited to 'src') diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp index 47bbb6b0..f4b47097 100644 --- a/src/apps/cam/drm.cpp +++ b/src/apps/cam/drm.cpp @@ -450,8 +450,6 @@ int Device::openCard() } for (struct dirent *res; (res = readdir(folder));) { - uint64_t cap; - if (strncmp(res->d_name, "card", 4)) continue; @@ -465,15 +463,22 @@ int Device::openCard() } /* - * Skip devices that don't support the modeset API, to avoid - * selecting a DRM device corresponding to a GPU. There is no - * modeset capability, but the kernel returns an error for most - * caps if mode setting isn't support by the driver. The - * DRM_CAP_DUMB_BUFFER capability is one of those, other would - * do as well. The capability value itself isn't relevant. + * Skip non-display devices. While this could in theory be done + * by checking for support of the mode setting API, some + * out-of-tree render-only GPU drivers (namely powervr) + * incorrectly set the DRIVER_MODESET driver feature. Check for + * the presence of at least one CRTC, encoder and connector + * instead. */ - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap); - if (ret < 0) { + std::unique_ptr resources{ + drmModeGetResources(fd_), + &drmModeFreeResources + }; + if (!resources || + resources->count_connectors <= 0 || + resources->count_crtcs <= 0 || + resources->count_encoders <= 0) { + resources.reset(); drmClose(fd_); fd_ = -1; continue; -- cgit v1.2.1