[{"id":25160,"web_url":"https://patchwork.libcamera.org/comment/25160/","msgid":"","date":"2022-09-28T11:26:24","subject":"Re: [libcamera-devel] [PATCH v2] cam: drm: Skip DRM devices not\n\tcapable of mode setting","submitter":{"id":101,"url":"https://patchwork.libcamera.org/api/people/101/","name":"Eric Curtin","email":"ecurtin@redhat.com"},"content":"On Wed, 28 Sept 2022 at 11:27, Laurent Pinchart\n wrote:\n>\n> The DRM helper picks the first DRM card that it can open. On platforms\n> that have a standalone GPU, this risks selecting a device corresponding\n> to the GPU instead of the display controller. Fix this by skipping\n> devices that don't support the KMS mode setting API. Some legacy display\n> controllers would be skipped as well, but libcamera doesn't run on those\n> systems anyway.\n>\n> Signed-off-by: Laurent Pinchart \n> ---\n> Changes since v1:\n>\n> - Use DRM_CAP_DUMB_BUFFER instead of DRM_CLIENT_CAP_ATOMIC\n> ---\n> src/cam/drm.cpp | 35 +++++++++++++++++++++++++++--------\n> 1 file changed, 27 insertions(+), 8 deletions(-)\n>\n> diff --git a/src/cam/drm.cpp b/src/cam/drm.cpp\n> index b0602c942853..3bb950fd157a 100644\n> --- a/src/cam/drm.cpp\n> +++ b/src/cam/drm.cpp\n> @@ -430,7 +430,8 @@ int Device::init()\n> int Device::openCard()\n> {\n> const std::string dirName = \"/dev/dri/\";\n> - int ret = -ENOENT;\n> + bool found = false;\n> + int ret;\n>\n> /*\n> * Open the first DRM/KMS device beginning with /dev/dri/card. The\n> @@ -449,24 +450,42 @@ 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> const std::string devName = dirName + res->d_name;\n> fd_ = open(devName.c_str(), O_RDWR | O_CLOEXEC);\n> - if (fd_ >= 0) {\n> - ret = 0;\n> - break;\n> + if (fd_ < 0) {\n> + ret = -errno;\n> + std::cerr << \"Failed to open DRM/KMS device \" << devName << \": \"\n> + << strerror(-ret) << std::endl;\n> + continue;\n> }\n>\n> - ret = -errno;\n> - std::cerr << \"Failed to open DRM/KMS device \" << devName << \": \"\n> - << strerror(-ret) << std::endl;\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 but 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\nSince this ends up being an ioctl I guess this is fine. In modetest.c\nthey do it the `if (ret || cap == 0)` way, but a failed ioctl returns\n-1 so this is fine too. Plus the author of that code in modetest.c is\nLaurent Pinchart in 2014 :)\n\nReviewed-by: Eric Curtin \n\n\n> + drmClose(fd_);\n> + fd_ = -1;\n> + continue;\n> + }\n> +\n> + found = true;\n> + break;\n> }\n>\n> closedir(folder);\n>\n> - return ret;\n> + return found ? 0 : -ENOENT;\n> }\n>\n> int Device::getResources()\n> --\n> Regards,\n>\n> Laurent Pinchart\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 2C393C0DA4\n\tfor ;\n\tWed, 28 Sep 2022 11:26:46 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 85EE7622A5;\n\tWed, 28 Sep 2022 13:26:45 +0200 (CEST)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.133.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id F2F286224C\n\tfor ;\n\tWed, 28 Sep 2022 13:26:43 +0200 (CEST)","from mail-vs1-f71.google.com (mail-vs1-f71.google.com\n\t[209.85.217.71]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id\n\tus-mta-468--Lm9l6OpN_yiI2om1mQGmA-1; 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\n\tWed, 28 Sep 2022 04:26:41 -0700 (PDT)","by 2002:a67:f855:0:b0:39a:c07e:4233 with SMTP id\n\tb21-20020a67f855000000b0039ac07e4233mr15965494vsp.13.1664364401032;\n\tWed, 28 Sep 2022 04:26:41 -0700 (PDT)"],"X-Google-Smtp-Source":"AMsMyM6WLqyT/l4aJcJIqo36Ad1+bQgq8xCp4sQwPzhNr5Ps6oNrajLhSRveBTyk9B+4ehE1cr/4KdlPv0fqxnoIhOs=","MIME-Version":"1.0","References":"<20220928102743.1484-1-laurent.pinchart@ideasonboard.com>","In-Reply-To":"<20220928102743.1484-1-laurent.pinchart@ideasonboard.com>","Date":"Wed, 28 Sep 2022 12:26:24 +0100","Message-ID":"","To":"Laurent Pinchart ","X-Mimecast-Spam-Score":"0","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain; charset=\"UTF-8\"","Subject":"Re: [libcamera-devel] [PATCH v2] cam: drm: Skip DRM devices not\n\tcapable of mode setting","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","From":"Eric Curtin via libcamera-devel ","Reply-To":"Eric Curtin ","Cc":"libcamera-devel@lists.libcamera.org","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":25164,"web_url":"https://patchwork.libcamera.org/comment/25164/","msgid":"<20220928132955.biil323gfkvfa2ci@uno.localdomain>","date":"2022-09-28T13:29:55","subject":"Re: [libcamera-devel] [PATCH v2] cam: drm: Skip DRM devices not\n\tcapable of mode setting","submitter":{"id":3,"url":"https://patchwork.libcamera.org/api/people/3/","name":"Jacopo Mondi","email":"jacopo@jmondi.org"},"content":"Hi Laurent,\n\nOn Wed, Sep 28, 2022 at 01:27:43PM +0300, Laurent Pinchart via libcamera-devel wrote:\n> The DRM helper picks the first DRM card that it can open. On platforms\n> that have a standalone GPU, this risks selecting a device corresponding\n> to the GPU instead of the display controller. Fix this by skipping\n> devices that don't support the KMS mode setting API. Some legacy display\n> controllers would be skipped as well, but libcamera doesn't run on those\n> systems anyway.\n>\n> Signed-off-by: Laurent Pinchart \n> ---\n> Changes since v1:\n>\n> - Use DRM_CAP_DUMB_BUFFER instead of DRM_CLIENT_CAP_ATOMIC\n> ---\n> src/cam/drm.cpp | 35 +++++++++++++++++++++++++++--------\n> 1 file changed, 27 insertions(+), 8 deletions(-)\n>\n> diff --git a/src/cam/drm.cpp b/src/cam/drm.cpp\n> index b0602c942853..3bb950fd157a 100644\n> --- a/src/cam/drm.cpp\n> +++ b/src/cam/drm.cpp\n> @@ -430,7 +430,8 @@ int Device::init()\n> int Device::openCard()\n> {\n> \tconst std::string dirName = \"/dev/dri/\";\n> -\tint ret = -ENOENT;\n> +\tbool found = false;\n> +\tint ret;\n>\n> \t/*\n> \t * Open the first DRM/KMS device beginning with /dev/dri/card. The\n> @@ -449,24 +450,42 @@ int Device::openCard()\n> \t}\n>\n> \tfor (struct dirent *res; (res = readdir(folder));) {\n> +\t\tuint64_t cap;\n> +\n> \t\tif (strncmp(res->d_name, \"card\", 4))\n> \t\t\tcontinue;\n>\n> \t\tconst std::string devName = dirName + res->d_name;\n> \t\tfd_ = open(devName.c_str(), O_RDWR | O_CLOEXEC);\n> -\t\tif (fd_ >= 0) {\n> -\t\t\tret = 0;\n> -\t\t\tbreak;\n> +\t\tif (fd_ < 0) {\n> +\t\t\tret = -errno;\n> +\t\t\tstd::cerr << \"Failed to open DRM/KMS device \" << devName << \": \"\n> +\t\t\t\t << strerror(-ret) << std::endl;\n> +\t\t\tcontinue;\n> \t\t}\n>\n> -\t\tret = -errno;\n> -\t\tstd::cerr << \"Failed to open DRM/KMS device \" << devName << \": \"\n> -\t\t\t << strerror(-ret) << std::endl;\n> +\t\t/*\n> +\t\t * Skip devices that don't support the modeset API, to avoid\n> +\t\t * selecting a DRM device corresponding to a GPU. There is no\n> +\t\t * modeset capability, but the kernel returns an error for most\n> +\t\t * caps if mode setting isn't support but the driver. The\n\ns/but/by ?\n\n> +\t\t * DRM_CAP_DUMB_BUFFER capability is one of those, other would\n> +\t\t * do as well. The capability value itself isn't relevant.\n\nThat's a really awful API :)\n\nFor this patch\nReviewed-by: Jacopo Mondi \n\nThanks\n j\n\n\n> +\t\t */\n> +\t\tret = drmGetCap(fd_, DRM_CAP_DUMB_BUFFER, &cap);\n> +\t\tif (ret < 0) {\n> +\t\t\tdrmClose(fd_);\n> +\t\t\tfd_ = -1;\n> +\t\t\tcontinue;\n> +\t\t}\n> +\n> +\t\tfound = true;\n> +\t\tbreak;\n> \t}\n>\n> \tclosedir(folder);\n>\n> -\treturn ret;\n> +\treturn found ? 0 : -ENOENT;\n> }\n>\n> int Device::getResources()\n> --\n> Regards,\n>\n> Laurent Pinchart\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 4DBD3BD16B\n\tfor ;\n\tWed, 28 Sep 2022 13:30:00 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id AD65C622B0;\n\tWed, 28 Sep 2022 15:29:59 +0200 (CEST)","from relay10.mail.gandi.net (relay10.mail.gandi.net\n\t[IPv6:2001:4b98:dc4:8::230])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 71348622A6\n\tfor ;\n\tWed, 28 Sep 2022 15:29:58 +0200 (CEST)","(Authenticated sender: jacopo@jmondi.org)\n\tby mail.gandi.net (Postfix) with ESMTPSA id AC94D24000B;\n\tWed, 28 Sep 2022 13:29:57 +0000 (UTC)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=libcamera.org;\n\ts=mail; t=1664371799;\n\tbh=BsXA5OoHK+B9SnhsJwGL2nXtxBX325mF02EyXRgUSH0=;\n\th=Date:To:References:In-Reply-To:Subject:List-Id:List-Unsubscribe:\n\tList-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:\n\tFrom;\n\tb=Hzopt6d44MPhLDGJUJcxdPTW0HY5u9Q10PcHMDUkDWvuTFyIJGe9ftH4qwFQovSYF\n\tC/j9mOW3NL6GaiLCkennUpAQrNuClyhzR1P79K6nJ0NYFg+0Na4cF6RDQKwbfmHfTe\n\tuqn1N90Obs1Dpr2l0O22DsyKWGwq2dPHPS8kkX2nilVt8jcZxwuLgw2CIpbZKCuA3I\n\tcRmPZmPL4VwYeEuGO4Jm8a1Dw/JOIjG8JTU1qOEMnsryPeFpjiRcHwj0SB4DY09izW\n\thqQeo6OxkyAspYU7GVdI1oVQuy+XF6Xhk7u8tfGoWjl6h2qutlfqdnekJvUpg7EjAn\n\t5NsKb4/uR5WWw==","Date":"Wed, 28 Sep 2022 15:29:55 +0200","To":"Laurent Pinchart ","Message-ID":"<20220928132955.biil323gfkvfa2ci@uno.localdomain>","References":"<20220928102743.1484-1-laurent.pinchart@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20220928102743.1484-1-laurent.pinchart@ideasonboard.com>","Subject":"Re: [libcamera-devel] [PATCH v2] cam: drm: Skip DRM devices not\n\tcapable of mode setting","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","From":"Jacopo Mondi via libcamera-devel ","Reply-To":"Jacopo Mondi ","Cc":"libcamera-devel@lists.libcamera.org","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]