[{"id":34381,"web_url":"https://patchwork.libcamera.org/comment/34381/","msgid":"<174852771033.896144.16226091823091754721@ping.linuxembedded.co.uk>","date":"2025-05-29T14:08:30","subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Quoting Milan Zamazal (2025-05-29 09:23:26)\n> Device::openCard() in the cam DRM helpers looks for a /dev/dri/card*\n> device that can be opened and that doesn't fail when asked about\n> DRM_CAP_DUMB_BUFFER capability (regardless whether the capability is\n> supported by the device).\n> \n> There can be matching devices that are not display devices. This can\n> lead to selection of such a device and inability to use KMS output with\n> `cam' application. The ultimate goal is to display something on the\n> device and later the KMS sink will fail if there is no connector\n> attached to the device (although it can actually fail earlier, when\n> trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not\n> supported).\n> \n> Let's avoid selecting devices without connectors, CRTCs or encoders.\n> The added check makes the original check for DRM_CAP_DUMB_BUFFER API\n> most likely unnecessary, let's remove it.\n> \n> Changes in v3:\n> - Added checks for the presence of CRTCs and encoders.\n> - Removed the check for DRM_CAP_DUMB_BUFFER.\n> \n> Signed-off-by: Milan Zamazal \n> ---\n> src/apps/cam/drm.cpp | 22 ++++++++++------------\n> 1 file changed, 10 insertions(+), 12 deletions(-)\n> \n> diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp\n> index 47bbb6b05..c40c31410 100644\n> --- a/src/apps/cam/drm.cpp\n> +++ b/src/apps/cam/drm.cpp\n> @@ -450,8 +450,6 @@ int Device::openCard()\n> }\n> \n> for (struct dirent *res; (res = readdir(folder));) {\n> - uint64_t cap;\n> -\n> if (strncmp(res->d_name, \"card\", 4))\n> continue;\n> \n> @@ -464,16 +462,16 @@ int Device::openCard()\n> continue;\n> }\n> \n> - /*\n> - * Skip devices that don't support the modeset API, to avoid\n> - * selecting a DRM device corresponding to a GPU. There is no\n> - * modeset capability, but the kernel returns an error for most\n> - * caps if mode setting isn't support by the driver. The\n> - * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n> - * do as well. The capability value itself isn't relevant.\n> - */\n> - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n> - if (ret < 0) {\n> + /* Skip devices without connectors. */\n\nThis all sounds reasonable to me, though this comment now skips devices\nwithout connectors/crts/encoders.\n\nPerhaps we should update it while applying?\n\n\t\t/* Skip non-display devices */\n\n\nReviewed-by: Kieran Bingham \n\n> + std::unique_ptr resources{\n> + drmModeGetResources(fd_),\n> + &drmModeFreeResources\n> + };\n> + if (!resources ||\n> + resources->count_connectors <= 0 ||\n> + resources->count_crtcs <= 0 ||\n> + resources->count_encoders <= 0) {\n> + resources.reset();\n> drmClose(fd_);\n> fd_ = -1;\n> continue;\n> -- \n> 2.49.0\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id E2413C3237\n\tfor ;\n\tThu, 29 May 2025 14:08:37 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 9F75B68DA6;\n\tThu, 29 May 2025 16:08:36 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 34E15614CE\n\tfor ;\n\tThu, 29 May 2025 16:08:34 +0200 (CEST)","from pendragon.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id B3E4B6D5;\n\tThu, 29 May 2025 16:08:06 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"c9nIWTth\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1748527686;\n\tbh=QPDscVjFbwFnzKkCCUVbOD6vbPJQZZUtq6rREvTebOI=;\n\th=In-Reply-To:References:Subject:From:Cc:To:Date:From;\n\tb=c9nIWTthoISisRcQ04sXZKFwgPgpYrdLqMtGZgJOJFnRa1CVnIVU0psEY0PoqPZKO\n\ta70U/q3zAqC7G5PUq22vgYjwZGvqjHvLlefXuZp9wukwBLvSka7PH/L0AB681485T0\n\tcwDoct0sKvZbZV9OC8FEHGHmqk7XOvrxG9m4bKjU=","Content-Type":"text/plain; charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"quoted-printable","In-Reply-To":"<20250529082326.25156-1-mzamazal@redhat.com>","References":"<20250529082326.25156-1-mzamazal@redhat.com>","Subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","From":"Kieran Bingham ","Cc":"Milan Zamazal ,\n\tMattijs Korpershoek ,\n\tLaurent Pinchart ","To":"Milan Zamazal , libcamera-devel@lists.libcamera.org","Date":"Thu, 29 May 2025 15:08:30 +0100","Message-ID":"<174852771033.896144.16226091823091754721@ping.linuxembedded.co.uk>","User-Agent":"alot/0.9.1","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":34382,"web_url":"https://patchwork.libcamera.org/comment/34382/","msgid":"<85cybriih1.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2025-05-29T14:45:14","subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Kieran Bingham writes:\n\n> Quoting Milan Zamazal (2025-05-29 09:23:26)\n>> Device::openCard() in the cam DRM helpers looks for a /dev/dri/card*\n>> device that can be opened and that doesn't fail when asked about\n>\n>> DRM_CAP_DUMB_BUFFER capability (regardless whether the capability is\n>> supported by the device).\n>> \n>> There can be matching devices that are not display devices. This can\n>> lead to selection of such a device and inability to use KMS output with\n>> `cam' application. The ultimate goal is to display something on the\n>> device and later the KMS sink will fail if there is no connector\n>> attached to the device (although it can actually fail earlier, when\n>> trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not\n>> supported).\n>> \n>> Let's avoid selecting devices without connectors, CRTCs or encoders.\n>> The added check makes the original check for DRM_CAP_DUMB_BUFFER API\n>> most likely unnecessary, let's remove it.\n>> \n>> Changes in v3:\n>> - Added checks for the presence of CRTCs and encoders.\n>> - Removed the check for DRM_CAP_DUMB_BUFFER.\n>> \n>> Signed-off-by: Milan Zamazal \n>> ---\n>> src/apps/cam/drm.cpp | 22 ++++++++++------------\n>> 1 file changed, 10 insertions(+), 12 deletions(-)\n>> \n>> diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp\n>> index 47bbb6b05..c40c31410 100644\n>> --- a/src/apps/cam/drm.cpp\n>> +++ b/src/apps/cam/drm.cpp\n>> @@ -450,8 +450,6 @@ int Device::openCard()\n>> }\n>> \n>> for (struct dirent *res; (res = readdir(folder));) {\n>> - uint64_t cap;\n>> -\n>> if (strncmp(res->d_name, \"card\", 4))\n>> continue;\n>> \n>> @@ -464,16 +462,16 @@ int Device::openCard()\n>> continue;\n>> }\n>> \n>> - /*\n>> - * Skip devices that don't support the modeset API, to avoid\n>> - * selecting a DRM device corresponding to a GPU. There is no\n>> - * modeset capability, but the kernel returns an error for most\n>> - * caps if mode setting isn't support by the driver. The\n>> - * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n>> - * do as well. The capability value itself isn't relevant.\n>> - */\n>> - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n>> - if (ret < 0) {\n>> + /* Skip devices without connectors. */\n>\n> This all sounds reasonable to me, though this comment now skips devices\n> without connectors/crts/encoders.\n>\n> Perhaps we should update it while applying?\n>\n> \t\t/* Skip non-display devices */\n\nAh, yes, please.\n\n> Reviewed-by: Kieran Bingham \n>\n>> + std::unique_ptr resources{\n>> + drmModeGetResources(fd_),\n>> + &drmModeFreeResources\n>> + };\n>> + if (!resources ||\n>> + resources->count_connectors <= 0 ||\n>> + resources->count_crtcs <= 0 ||\n>> + resources->count_encoders <= 0) {\n>> + resources.reset();\n>> drmClose(fd_);\n>> fd_ = -1;\n>> continue;\n>> -- \n>> 2.49.0\n>>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id DB665C3237\n\tfor ;\n\tThu, 29 May 2025 14:45:23 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 033FA68D94;\n\tThu, 29 May 2025 16:45:23 +0200 (CEST)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.129.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 6ABD6614CE\n\tfor ;\n\tThu, 29 May 2025 16:45:20 +0200 (CEST)","from mail-wm1-f70.google.com (mail-wm1-f70.google.com\n\t[209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-31-Da41qGkTONy7-Zv66HSKCA-1; Thu, 29 May 2025 10:45:17 -0400","by mail-wm1-f70.google.com with SMTP id\n\t5b1f17b1804b1-450cb8f8b1bso2901595e9.3\n\tfor ;\n\tThu, 29 May 2025 07:45:17 -0700 (PDT)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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This can\n>> lead to selection of such a device and inability to use KMS output with\n>> `cam' application. The ultimate goal is to display something on the\n>> device and later the KMS sink will fail if there is no connector\n>> attached to the device (although it can actually fail earlier, when\n>> trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not\n>> supported).\n>> \n>> Let's avoid selecting devices without connectors, CRTCs or encoders.\n>> The added check makes the original check for DRM_CAP_DUMB_BUFFER API\n>> most likely unnecessary, let's remove it.\n>> \n>> Changes in v3:\n>> - Added checks for the presence of CRTCs and encoders.\n>> - Removed the check for DRM_CAP_DUMB_BUFFER.\n>> \n>> Signed-off-by: Milan Zamazal \n>> ---\n>> src/apps/cam/drm.cpp | 22 ++++++++++------------\n>> 1 file changed, 10 insertions(+), 12 deletions(-)\n>> \n>> diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp\n>> index 47bbb6b05..c40c31410 100644\n>> --- a/src/apps/cam/drm.cpp\n>> +++ b/src/apps/cam/drm.cpp\n>> @@ -450,8 +450,6 @@ int Device::openCard()\n>> }\n>> \n>> for (struct dirent *res; (res = readdir(folder));) {\n>> - uint64_t cap;\n>> -\n>> if (strncmp(res->d_name, \"card\", 4))\n>> continue;\n>> \n>> @@ -464,16 +462,16 @@ int Device::openCard()\n>> continue;\n>> }\n>> \n>> - /*\n>> - * Skip devices that don't support the modeset API, to avoid\n>> - * selecting a DRM device corresponding to a GPU. There is no\n>> - * modeset capability, but the kernel returns an error for most\n>> - * caps if mode setting isn't support by the driver. The\n>> - * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n>> - * do as well. The capability value itself isn't relevant.\n>> - */\n>> - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n>> - if (ret < 0) {\n>> + /* Skip devices without connectors. */\n>\n> This all sounds reasonable to me, though this comment now skips devices\n> without connectors/crts/encoders.\n>\n> Perhaps we should update it while applying?\n>\n> \t\t/* Skip non-display devices */\n\nI agree with the fixup.\n\nIf it's applied, then:\n\nReviewed-by: Mattijs Korpershoek \n\n>\n>\n> Reviewed-by: Kieran Bingham \n>\n>> + std::unique_ptr resources{\n>> + drmModeGetResources(fd_),\n>> + &drmModeFreeResources\n>> + };\n>> + if (!resources ||\n>> + resources->count_connectors <= 0 ||\n>> + resources->count_crtcs <= 0 ||\n>> + resources->count_encoders <= 0) {\n>> + resources.reset();\n>> drmClose(fd_);\n>> fd_ = -1;\n>> continue;\n>> -- \n>> 2.49.0\n>>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 57AD7C3237\n\tfor ;\n\tFri, 30 May 2025 07:05:49 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 3407668DA8;\n\tFri, 30 May 2025 09:05:48 +0200 (CEST)","from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 612FB614D5\n\tfor ;\n\tFri, 30 May 2025 09:05:45 +0200 (CEST)","from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58])\n\tby tor.source.kernel.org (Postfix) with ESMTP id 2FF956115E;\n\tFri, 30 May 2025 07:05:44 +0000 (UTC)","by smtp.kernel.org (Postfix) with ESMTPSA id 83997C4CEE9;\n\tFri, 30 May 2025 07:05:43 +0000 (UTC)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (2048-bit key;\n\tunprotected) header.d=kernel.org header.i=@kernel.org\n\theader.b=\"ZHU0M60I\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n\ts=k20201202; t=1748588743;\n\tbh=UrxxI7qyXVsqZ0DXQnXFS9i+ihfdtlhvAL2267EM9EI=;\n\th=From:To:Cc:Subject:In-Reply-To:References:Date:From;\n\tb=ZHU0M60ILDhiA+9dP7W1FdKiUj5PqgEDASKyPND0wQHcwTQv91X6uC5+TSxvLty9t\n\tZVIxGheRpj6JsmfhuVyTzLV4sjdelQPrVrl+Oqt+zDGgCaNGcYHymEufkptqlscpDb\n\tvEck+IA0HOrAybb9uokmf4RQpwjVDkT9sVLfh8iGclR4usX+pQGadCoSNc6AKO/ajI\n\tgf8kauO8p3Y7RVehgv54fw+HnGZ8k0QLxVtSZIGOQ41UDl4JXvj7X/Yu8110Q9LXFu\n\tGxLdoU8+g2KgZ7YhgwVlbo/5ZdtG4S85TZbEDVOR8ZCw+eSIAJ6+ReBgDRtjq2Tt4Y\n\tgvHUuH+i/8NDQ==","From":"Mattijs Korpershoek ","To":"Kieran Bingham , Milan Zamazal\n\t, libcamera-devel@lists.libcamera.org","Cc":"Milan Zamazal , Mattijs Korpershoek\n\t, Laurent Pinchart\n\t","Subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","In-Reply-To":"<174852771033.896144.16226091823091754721@ping.linuxembedded.co.uk>","References":"<20250529082326.25156-1-mzamazal@redhat.com>\n\t<174852771033.896144.16226091823091754721@ping.linuxembedded.co.uk>","Date":"Fri, 30 May 2025 09:05:41 +0200","Message-ID":"<87sekmpohm.fsf@kernel.org>","MIME-Version":"1.0","Content-Type":"text/plain","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":34386,"web_url":"https://patchwork.libcamera.org/comment/34386/","msgid":"<20250530083255.GS12492@pendragon.ideasonboard.com>","date":"2025-05-30T08:32:55","subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Fri, May 30, 2025 at 09:05:41AM +0200, Mattijs Korpershoek wrote:\n> On jeu., mai 29, 2025 at 15:08, Kieran Bingham wrote:\n> > Quoting Milan Zamazal (2025-05-29 09:23:26)\n> >> Device::openCard() in the cam DRM helpers looks for a /dev/dri/card*\n> >> device that can be opened and that doesn't fail when asked about\n> >> DRM_CAP_DUMB_BUFFER capability (regardless whether the capability is\n> >> supported by the device).\n> >> \n> >> There can be matching devices that are not display devices. This can\n> >> lead to selection of such a device and inability to use KMS output with\n> >> `cam' application. The ultimate goal is to display something on the\n> >> device and later the KMS sink will fail if there is no connector\n> >> attached to the device (although it can actually fail earlier, when\n> >> trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not\n> >> supported).\n> >> \n> >> Let's avoid selecting devices without connectors, CRTCs or encoders.\n> >> The added check makes the original check for DRM_CAP_DUMB_BUFFER API\n> >> most likely unnecessary, let's remove it.\n> >> \n> >> Changes in v3:\n> >> - Added checks for the presence of CRTCs and encoders.\n> >> - Removed the check for DRM_CAP_DUMB_BUFFER.\n> >> \n> >> Signed-off-by: Milan Zamazal \n> >> ---\n> >> src/apps/cam/drm.cpp | 22 ++++++++++------------\n> >> 1 file changed, 10 insertions(+), 12 deletions(-)\n> >> \n> >> diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp\n> >> index 47bbb6b05..c40c31410 100644\n> >> --- a/src/apps/cam/drm.cpp\n> >> +++ b/src/apps/cam/drm.cpp\n> >> @@ -450,8 +450,6 @@ int Device::openCard()\n> >> }\n> >> \n> >> for (struct dirent *res; (res = readdir(folder));) {\n> >> - uint64_t cap;\n> >> -\n> >> if (strncmp(res->d_name, \"card\", 4))\n> >> continue;\n> >> \n> >> @@ -464,16 +462,16 @@ int Device::openCard()\n> >> continue;\n> >> }\n> >> \n> >> - /*\n> >> - * Skip devices that don't support the modeset API, to avoid\n> >> - * selecting a DRM device corresponding to a GPU. There is no\n> >> - * modeset capability, but the kernel returns an error for most\n> >> - * caps if mode setting isn't support by the driver. The\n> >> - * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n> >> - * do as well. The capability value itself isn't relevant.\n> >> - */\n> >> - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n> >> - if (ret < 0) {\n> >> + /* Skip devices without connectors. */\n> >\n> > This all sounds reasonable to me, though this comment now skips devices\n> > without connectors/crts/encoders.\n> >\n> > Perhaps we should update it while applying?\n> >\n> > \t\t/* Skip non-display devices */\n> \n> I agree with the fixup.\n\nI would expand it a bit\n\n \t\t/*\n\t\t * Skip non-display devices. While this could in theory be done\n\t\t * by checking for support of the mode setting API, some\n\t\t * out-of-tree render-only GPU drivers (namely powervr)\n\t\t * incorrectly set the DRIVER_MODESET driver feature. Check for\n\t\t * the presence of at least one CRTC, encoder and connector\n\t\t * instead.\n\t\t */\n\nReviewed-by: Laurent Pinchart \n\n> If it's applied, then:\n> \n> Reviewed-by: Mattijs Korpershoek \n> \n> > Reviewed-by: Kieran Bingham \n> >\n> >> + std::unique_ptr resources{\n> >> + drmModeGetResources(fd_),\n> >> + &drmModeFreeResources\n> >> + };\n> >> + if (!resources ||\n> >> + resources->count_connectors <= 0 ||\n> >> + resources->count_crtcs <= 0 ||\n> >> + resources->count_encoders <= 0) {\n> >> + resources.reset();\n> >> drmClose(fd_);\n> >> fd_ = -1;\n> >> continue;","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 5DE91C3237\n\tfor ;\n\tFri, 30 May 2025 08:33:06 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id E171568D9E;\n\tFri, 30 May 2025 10:33:04 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id B8768614D5\n\tfor ;\n\tFri, 30 May 2025 10:33:02 +0200 (CEST)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 8F10B89A;\n\tFri, 30 May 2025 10:32:34 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"juszyLIN\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1748593954;\n\tbh=nR391Utw3K6+2JrhLh8qT1vt3aaX/Nme1fG29q7xavo=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=juszyLIN+gVU9AKEBDcSdSkqpkZTlvJ2UppV6P47RKnhb3CyKi8pjGsdVqBRM8qTy\n\tK/6uS3dEnkK7mUEpTT8cncbmg+n/PiaT8qsZm33OF3TEffApdDbdXFmBTHcPWWoUsx\n\tTp8ngkfl8YJKUKjrWO1KQH5KSundgAwZ/roLQzUo=","Date":"Fri, 30 May 2025 11:32:55 +0300","From":"Laurent Pinchart ","To":"Mattijs Korpershoek ","Cc":"Kieran Bingham ,\n\tMilan Zamazal , libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","Message-ID":"<20250530083255.GS12492@pendragon.ideasonboard.com>","References":"<20250529082326.25156-1-mzamazal@redhat.com>\n\t<174852771033.896144.16226091823091754721@ping.linuxembedded.co.uk>\n\t<87sekmpohm.fsf@kernel.org>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<87sekmpohm.fsf@kernel.org>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":34389,"web_url":"https://patchwork.libcamera.org/comment/34389/","msgid":"<85msauqxae.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2025-05-30T09:10:17","subject":"Re: [PATCH v3] apps: cam: Skip non-display GPUs","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Laurent Pinchart writes:\n\n> On Fri, May 30, 2025 at 09:05:41AM +0200, Mattijs Korpershoek wrote:\n>> On jeu., mai 29, 2025 at 15:08, Kieran Bingham wrote:\n>> > Quoting Milan Zamazal (2025-05-29 09:23:26)\n>\n>> >> Device::openCard() in the cam DRM helpers looks for a /dev/dri/card*\n>> >> device that can be opened and that doesn't fail when asked about\n>> >> DRM_CAP_DUMB_BUFFER capability (regardless whether the capability is\n>> >> supported by the device).\n>> >> \n>> >> There can be matching devices that are not display devices. This can\n>> >> lead to selection of such a device and inability to use KMS output with\n>> >> `cam' application. The ultimate goal is to display something on the\n>> >> device and later the KMS sink will fail if there is no connector\n>> >> attached to the device (although it can actually fail earlier, when\n>> >> trying to set DRM_CLIENT_CAP_ATOMIC capability if this is not\n>> >> supported).\n>> >> \n>> >> Let's avoid selecting devices without connectors, CRTCs or encoders.\n>> >> The added check makes the original check for DRM_CAP_DUMB_BUFFER API\n>> >> most likely unnecessary, let's remove it.\n>> >> \n>> >> Changes in v3:\n>> >> - Added checks for the presence of CRTCs and encoders.\n>> >> - Removed the check for DRM_CAP_DUMB_BUFFER.\n>> >> \n>> >> Signed-off-by: Milan Zamazal \n>> >> ---\n>> >> src/apps/cam/drm.cpp | 22 ++++++++++------------\n>> >> 1 file changed, 10 insertions(+), 12 deletions(-)\n>> >> \n>> >> diff --git a/src/apps/cam/drm.cpp b/src/apps/cam/drm.cpp\n>> >> index 47bbb6b05..c40c31410 100644\n>> >> --- a/src/apps/cam/drm.cpp\n>> >> +++ b/src/apps/cam/drm.cpp\n>> >> @@ -450,8 +450,6 @@ int Device::openCard()\n>> >> }\n>> >> \n>> >> for (struct dirent *res; (res = readdir(folder));) {\n>> >> - uint64_t cap;\n>> >> -\n>> >> if (strncmp(res->d_name, \"card\", 4))\n>> >> continue;\n>> >> \n>> >> @@ -464,16 +462,16 @@ int Device::openCard()\n>> >> continue;\n>> >> }\n>> >> \n>> >> - /*\n>> >> - * Skip devices that don't support the modeset API, to avoid\n>> >> - * selecting a DRM device corresponding to a GPU. There is no\n>> >> - * modeset capability, but the kernel returns an error for most\n>> >> - * caps if mode setting isn't support by the driver. The\n>> >> - * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n>> >> - * do as well. The capability value itself isn't relevant.\n>> >> - */\n>> >> - ret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n>> >> - if (ret < 0) {\n>> >> + /* Skip devices without connectors. */\n>> >\n>> > This all sounds reasonable to me, though this comment now skips devices\n>> > without connectors/crts/encoders.\n>> >\n>> > Perhaps we should update it while applying?\n>> >\n>> > \t\t/* Skip non-display devices */\n>> \n>> I agree with the fixup.\n>\n> I would expand it a bit\n>\n> \t\t/*\n> \t\t * Skip non-display devices. While this could in theory be done\n> \t\t * by checking for support of the mode setting API, some\n> \t\t * out-of-tree render-only GPU drivers (namely powervr)\n> \t\t * incorrectly set the DRIVER_MODESET driver feature. Check for\n> \t\t * the presence of at least one CRTC, encoder and connector\n> \t\t * instead.\n> \t\t */\n\nYes, thank you, done in v4 (the only change there).\n\n> Reviewed-by: Laurent Pinchart \n>\n>> If it's applied, then:\n>> \n>> Reviewed-by: Mattijs Korpershoek \n>> \n>> > Reviewed-by: Kieran Bingham \n>> >\n>> >> + std::unique_ptr resources{\n>> >> + drmModeGetResources(fd_),\n>> >> + &drmModeFreeResources\n>> >> + };\n>> >> + if (!resources ||\n>> >> + resources->count_connectors <= 0 ||\n>> >> + resources->count_crtcs <= 0 ||\n>> >> + resources->count_encoders <= 0) {\n>> >> + resources.reset();\n>> >> drmClose(fd_);\n>> >> fd_ = -1;\n>> >> continue;","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 8D13FC3237\n\tfor ;\n\tFri, 30 May 2025 09:10:25 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 963DA68DA8;\n\tFri, 30 May 2025 11:10:24 +0200 (CEST)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.129.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 884A3614D5\n\tfor ;\n\tFri, 30 May 2025 11:10:23 +0200 (CEST)","from mail-wm1-f71.google.com (mail-wm1-f71.google.com\n\t[209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-623-MGhOgxBoOwOlLlLDRIakTg-1; Fri, 30 May 2025 05:10:21 -0400","by mail-wm1-f71.google.com with SMTP id\n\t5b1f17b1804b1-450d64026baso4263635e9.1\n\tfor ;\n\tFri, 30 May 2025 02:10:21 -0700 (PDT)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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