[{"id":34664,"web_url":"https://patchwork.libcamera.org/comment/34664/","msgid":"<20250626131450.GR8738@pendragon.ideasonboard.com>","date":"2025-06-26T13:14:50","subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Wed, Jun 25, 2025 at 04:53:08PM +0100, Daniel Scally wrote:\n> Some kernel drivers give their entities names that will differ from\n> implementation to implementation; for example the drivers for the\n> Camera Receiver Unit and CSI-2 receiver in the RZ/V2H SoC give their\n> entities names that include their memory address, in the format\n> \"csi-16000400.csi2\". Passing that entity name to\n> MediaDevice::getEntityByName() is too inflexible given it would only\n> then work if that specific CSI-2 receiver were the one being used.\n> \n> Update MediaDevice::getEntityByName() such that the string passed to\n> it is used to create a std::basic_regex, and use std::regex_search()\n> instead of a direct string comparison to find a matching entity. This\n> allows us to pass a string that will form a regex to match to the\n> entity instead, for example \"csi-[0-9]{8}.csi2\".\n> \n> Signed-off-by: Daniel Scally \n> ---\n> src/libcamera/media_device.cpp | 12 ++++++++----\n> src/libcamera/v4l2_subdevice.cpp | 4 ++--\n> 2 files changed, 10 insertions(+), 6 deletions(-)\n> \n> diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp\n> index 353f34a8..27180ca5 100644\n> --- a/src/libcamera/media_device.cpp\n> +++ b/src/libcamera/media_device.cpp\n> @@ -9,6 +9,7 @@\n> \n> #include \n> #include \n> +#include \n> #include \n> #include \n> #include \n> @@ -328,14 +329,17 @@ done:\n> */\n> \n> /**\n> - * \\brief Return the MediaEntity with name \\a name\n> - * \\param[in] name The entity name\n> - * \\return The entity with \\a name, or nullptr if no such entity is found\n> + * \\brief Return the MediaEntity with name matching the regex \\a name\n\n\"whose name matches\" ?\n\n> + * \\param[in] name Regex to match against the entity name\n> + * \\return The entity with name matching \\a name, or nullptr if no such entity\n> + * is found\n\nEntity names are unique, but with regex that's not the case anymore. If\nmultiple entities match the regex, the behaviour of this function will\nnot be predictable. Is that a concern ? It should at least be properly\ndocumented.\n\n> */\n> MediaEntity *MediaDevice::getEntityByName(const std::string &name) const\n> {\n> +\tstd::regex name_regex(name);\n> +\n> \tfor (MediaEntity *e : entities_)\n> -\t\tif (e->name() == name)\n> +\t\tif (std::regex_search(e->name(), name_regex))\n> \t\t\treturn e;\n> \n> \treturn nullptr;\n> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp\n> index 33279654..4868785d 100644\n> --- a/src/libcamera/v4l2_subdevice.cpp\n> +++ b/src/libcamera/v4l2_subdevice.cpp\n> @@ -1748,10 +1748,10 @@ const std::string &V4L2Subdevice::model()\n> */\n> \n> /**\n> - * \\brief Create a new video subdevice instance from \\a entity in media device\n> + * \\brief Create a new video subdevice instance from an entity in media device\n\n\"\\a entity\" refers to the entity parameter.\n\n> * \\a media\n> * \\param[in] media The media device where the entity is registered\n> - * \\param[in] entity The media entity name\n> + * \\param[in] entity A regex that will match media entity name\n> *\n> * \\return A newly created V4L2Subdevice on success, nullptr otherwise\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 2FDDFC3237\n\tfor ;\n\tThu, 26 Jun 2025 13:15:19 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 641AE68DF6;\n\tThu, 26 Jun 2025 15:15:17 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id CC01F68DE8\n\tfor ;\n\tThu, 26 Jun 2025 15:15:15 +0200 (CEST)","from pendragon.ideasonboard.com (85-76-34-12-nat.elisa-mobile.fi\n\t[85.76.34.12])\n\tby perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 631386AE;\n\tThu, 26 Jun 2025 15:14:56 +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=\"U+cPsRrL\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1750943696;\n\tbh=gkiCvXo2mBTlcaQ7MAzlzCpS+zX5KgUJ/Yd6kSViUsk=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=U+cPsRrLcGlHYpu0oCDnwddKqSShkdxxwGQARsD1GIovsLKte+YqPUFzguZudXmeh\n\tLy7IhYfV083Hhz2u4RtX2G0irXTtZRWg9GSgrqr0T0D72qmIGcBPY94sJwxfH+3bKi\n\tUCr1fgJhEqUY4Fsf81oTyrSUkMVbTcmEaKX//r2w=","Date":"Thu, 26 Jun 2025 16:14:50 +0300","From":"Laurent Pinchart ","To":"Daniel Scally ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","Message-ID":"<20250626131450.GR8738@pendragon.ideasonboard.com>","References":"<20250625155308.2325438-1-dan.scally@ideasonboard.com>\n\t<20250625155308.2325438-3-dan.scally@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20250625155308.2325438-3-dan.scally@ideasonboard.com>","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":34666,"web_url":"https://patchwork.libcamera.org/comment/34666/","msgid":"","date":"2025-06-26T13:29:02","subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","submitter":{"id":156,"url":"https://patchwork.libcamera.org/api/people/156/","name":"Dan Scally","email":"dan.scally@ideasonboard.com"},"content":"Hi Laurent\n\nOn 26/06/2025 14:14, Laurent Pinchart wrote:\n> On Wed, Jun 25, 2025 at 04:53:08PM +0100, Daniel Scally wrote:\n>> Some kernel drivers give their entities names that will differ from\n>> implementation to implementation; for example the drivers for the\n>> Camera Receiver Unit and CSI-2 receiver in the RZ/V2H SoC give their\n>> entities names that include their memory address, in the format\n>> \"csi-16000400.csi2\". Passing that entity name to\n>> MediaDevice::getEntityByName() is too inflexible given it would only\n>> then work if that specific CSI-2 receiver were the one being used.\n>>\n>> Update MediaDevice::getEntityByName() such that the string passed to\n>> it is used to create a std::basic_regex, and use std::regex_search()\n>> instead of a direct string comparison to find a matching entity. This\n>> allows us to pass a string that will form a regex to match to the\n>> entity instead, for example \"csi-[0-9]{8}.csi2\".\n>>\n>> Signed-off-by: Daniel Scally \n>> ---\n>> src/libcamera/media_device.cpp | 12 ++++++++----\n>> src/libcamera/v4l2_subdevice.cpp | 4 ++--\n>> 2 files changed, 10 insertions(+), 6 deletions(-)\n>>\n>> diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp\n>> index 353f34a8..27180ca5 100644\n>> --- a/src/libcamera/media_device.cpp\n>> +++ b/src/libcamera/media_device.cpp\n>> @@ -9,6 +9,7 @@\n>> \n>> #include \n>> #include \n>> +#include \n>> #include \n>> #include \n>> #include \n>> @@ -328,14 +329,17 @@ done:\n>> */\n>> \n>> /**\n>> - * \\brief Return the MediaEntity with name \\a name\n>> - * \\param[in] name The entity name\n>> - * \\return The entity with \\a name, or nullptr if no such entity is found\n>> + * \\brief Return the MediaEntity with name matching the regex \\a name\n> \"whose name matches\" ?\nSure\n>\n>> + * \\param[in] name Regex to match against the entity name\n>> + * \\return The entity with name matching \\a name, or nullptr if no such entity\n>> + * is found\n> Entity names are unique, but with regex that's not the case anymore. If\n> multiple entities match the regex, the behaviour of this function will\n> not be predictable. Is that a concern ? It should at least be properly\n> documented.\n\n\nI guess it might be...perhaps this should count the returned matches and complain heavily if the \nanswer is >1?\n\n>\n>> */\n>> MediaEntity *MediaDevice::getEntityByName(const std::string &name) const\n>> {\n>> +\tstd::regex name_regex(name);\n>> +\n>> \tfor (MediaEntity *e : entities_)\n>> -\t\tif (e->name() == name)\n>> +\t\tif (std::regex_search(e->name(), name_regex))\n>> \t\t\treturn e;\n>> \n>> \treturn nullptr;\n>> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp\n>> index 33279654..4868785d 100644\n>> --- a/src/libcamera/v4l2_subdevice.cpp\n>> +++ b/src/libcamera/v4l2_subdevice.cpp\n>> @@ -1748,10 +1748,10 @@ const std::string &V4L2Subdevice::model()\n>> */\n>> \n>> /**\n>> - * \\brief Create a new video subdevice instance from \\a entity in media device\n>> + * \\brief Create a new video subdevice instance from an entity in media device\n> \"\\a entity\" refers to the entity parameter.\nI think I changed that because the horrible regex string wouldn't necessarily be easily read as the \nentity anymore...but perhaps that's too persnickity\n>\n>> * \\a media\n>> * \\param[in] media The media device where the entity is registered\n>> - * \\param[in] entity The media entity name\n>> + * \\param[in] entity A regex that will match media entity name\n>> *\n>> * \\return A newly created V4L2Subdevice on success, nullptr otherwise\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 66EB9BDCBF\n\tfor ;\n\tThu, 26 Jun 2025 13:29:08 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 347DD68DF6;\n\tThu, 26 Jun 2025 15:29:07 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 20C6768DE8\n\tfor ;\n\tThu, 26 Jun 2025 15:29:05 +0200 (CEST)","from [192.168.0.43]\n\t(cpc141996-chfd3-2-0-cust928.12-3.cable.virginm.net [86.13.91.161])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 2ABFC833;\n\tThu, 26 Jun 2025 15:28:46 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; 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charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","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":34669,"web_url":"https://patchwork.libcamera.org/comment/34669/","msgid":"<20250626143836.GA5071@pendragon.ideasonboard.com>","date":"2025-06-26T14:38:36","subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Thu, Jun 26, 2025 at 02:29:02PM +0100, Daniel Scally wrote:\n> On 26/06/2025 14:14, Laurent Pinchart wrote:\n> > On Wed, Jun 25, 2025 at 04:53:08PM +0100, Daniel Scally wrote:\n> >> Some kernel drivers give their entities names that will differ from\n> >> implementation to implementation; for example the drivers for the\n> >> Camera Receiver Unit and CSI-2 receiver in the RZ/V2H SoC give their\n> >> entities names that include their memory address, in the format\n> >> \"csi-16000400.csi2\". Passing that entity name to\n> >> MediaDevice::getEntityByName() is too inflexible given it would only\n> >> then work if that specific CSI-2 receiver were the one being used.\n> >>\n> >> Update MediaDevice::getEntityByName() such that the string passed to\n> >> it is used to create a std::basic_regex, and use std::regex_search()\n> >> instead of a direct string comparison to find a matching entity. This\n> >> allows us to pass a string that will form a regex to match to the\n> >> entity instead, for example \"csi-[0-9]{8}.csi2\".\n> >>\n> >> Signed-off-by: Daniel Scally \n> >> ---\n> >> src/libcamera/media_device.cpp | 12 ++++++++----\n> >> src/libcamera/v4l2_subdevice.cpp | 4 ++--\n> >> 2 files changed, 10 insertions(+), 6 deletions(-)\n> >>\n> >> diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp\n> >> index 353f34a8..27180ca5 100644\n> >> --- a/src/libcamera/media_device.cpp\n> >> +++ b/src/libcamera/media_device.cpp\n> >> @@ -9,6 +9,7 @@\n> >> \n> >> #include \n> >> #include \n> >> +#include \n> >> #include \n> >> #include \n> >> #include \n> >> @@ -328,14 +329,17 @@ done:\n> >> */\n> >> \n> >> /**\n> >> - * \\brief Return the MediaEntity with name \\a name\n> >> - * \\param[in] name The entity name\n> >> - * \\return The entity with \\a name, or nullptr if no such entity is found\n> >> + * \\brief Return the MediaEntity with name matching the regex \\a name\n> > \n> > \"whose name matches\" ?\n> \n> Sure\n> \n> >> + * \\param[in] name Regex to match against the entity name\n> >> + * \\return The entity with name matching \\a name, or nullptr if no such entity\n> >> + * is found\n> > \n> > Entity names are unique, but with regex that's not the case anymore. If\n> > multiple entities match the regex, the behaviour of this function will\n> > not be predictable. Is that a concern ? It should at least be properly\n> > documented.\n> \n> I guess it might be...perhaps this should count the returned matches and complain heavily if the \n> answer is >1?\n\nIs that the most appropriate behaviour for the use cases you envision ?\nWhat are those use cases actually ?\n\n> >> */\n> >> MediaEntity *MediaDevice::getEntityByName(const std::string &name) const\n> >> {\n> >> +\tstd::regex name_regex(name);\n> >> +\n> >> \tfor (MediaEntity *e : entities_)\n> >> -\t\tif (e->name() == name)\n> >> +\t\tif (std::regex_search(e->name(), name_regex))\n> >> \t\t\treturn e;\n> >> \n> >> \treturn nullptr;\n> >> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp\n> >> index 33279654..4868785d 100644\n> >> --- a/src/libcamera/v4l2_subdevice.cpp\n> >> +++ b/src/libcamera/v4l2_subdevice.cpp\n> >> @@ -1748,10 +1748,10 @@ const std::string &V4L2Subdevice::model()\n> >> */\n> >> \n> >> /**\n> >> - * \\brief Create a new video subdevice instance from \\a entity in media device\n> >> + * \\brief Create a new video subdevice instance from an entity in media device\n> > \n> > \"\\a entity\" refers to the entity parameter.\n> \n> I think I changed that because the horrible regex string wouldn't necessarily be easily read as the \n> entity anymore...but perhaps that's too persnickity\n> \n> >> * \\a media\n> >> * \\param[in] media The media device where the entity is registered\n> >> - * \\param[in] entity The media entity name\n> >> + * \\param[in] entity A regex that will match media entity name\n> >> *\n> >> * \\return A newly created V4L2Subdevice on success, nullptr otherwise\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 66359C3237\n\tfor ;\n\tThu, 26 Jun 2025 14:39:01 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 6AB4268DF7;\n\tThu, 26 Jun 2025 16:39:00 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id B19CA68DE8\n\tfor ;\n\tThu, 26 Jun 2025 16:38:58 +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 UTF8SMTPSA id B4D15743;\n\tThu, 26 Jun 2025 16:38:39 +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=\"kuUagrhV\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1750948719;\n\tbh=WtsysfhhaAh0Ii6QBxgLIf32Tb7ggTXOX/xoB0m3uoc=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=kuUagrhVG0K9Gz+phVUURKPrdAxUP6dPLvZTM450taepp3X2/ltksCyWVKZxcWG6F\n\t7CVsuE1dUKAMTanqJEb5SDjP+TQiveSJQb4tlJintIP0Mt6UugXFnOw3AokVMEXZ+D\n\tKouvCGgNg7VDJS0hdxew8PSJEuOKoZAv/tpjiAQw=","Date":"Thu, 26 Jun 2025 17:38:36 +0300","From":"Laurent Pinchart ","To":"Dan Scally ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","Message-ID":"<20250626143836.GA5071@pendragon.ideasonboard.com>","References":"<20250625155308.2325438-1-dan.scally@ideasonboard.com>\n\t<20250625155308.2325438-3-dan.scally@ideasonboard.com>\n\t<20250626131450.GR8738@pendragon.ideasonboard.com>\n\t","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"","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":34902,"web_url":"https://patchwork.libcamera.org/comment/34902/","msgid":"","date":"2025-07-15T14:09:17","subject":"Re: [PATCH v1 2/2] libcamera: media_device: Use a regex to match\n\tentity name","submitter":{"id":156,"url":"https://patchwork.libcamera.org/api/people/156/","name":"Dan Scally","email":"dan.scally@ideasonboard.com"},"content":"Hi Laurent - sorry for not responding to this one more quickly\n\n\nOn 26/06/2025 15:38, Laurent Pinchart wrote:\n> On Thu, Jun 26, 2025 at 02:29:02PM +0100, Daniel Scally wrote:\n>> On 26/06/2025 14:14, Laurent Pinchart wrote:\n>>> On Wed, Jun 25, 2025 at 04:53:08PM +0100, Daniel Scally wrote:\n>>>> Some kernel drivers give their entities names that will differ from\n>>>> implementation to implementation; for example the drivers for the\n>>>> Camera Receiver Unit and CSI-2 receiver in the RZ/V2H SoC give their\n>>>> entities names that include their memory address, in the format\n>>>> \"csi-16000400.csi2\". Passing that entity name to\n>>>> MediaDevice::getEntityByName() is too inflexible given it would only\n>>>> then work if that specific CSI-2 receiver were the one being used.\n>>>>\n>>>> Update MediaDevice::getEntityByName() such that the string passed to\n>>>> it is used to create a std::basic_regex, and use std::regex_search()\n>>>> instead of a direct string comparison to find a matching entity. This\n>>>> allows us to pass a string that will form a regex to match to the\n>>>> entity instead, for example \"csi-[0-9]{8}.csi2\".\n>>>>\n>>>> Signed-off-by: Daniel Scally \n>>>> ---\n>>>> src/libcamera/media_device.cpp | 12 ++++++++----\n>>>> src/libcamera/v4l2_subdevice.cpp | 4 ++--\n>>>> 2 files changed, 10 insertions(+), 6 deletions(-)\n>>>>\n>>>> diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp\n>>>> index 353f34a8..27180ca5 100644\n>>>> --- a/src/libcamera/media_device.cpp\n>>>> +++ b/src/libcamera/media_device.cpp\n>>>> @@ -9,6 +9,7 @@\n>>>> \n>>>> #include \n>>>> #include \n>>>> +#include \n>>>> #include \n>>>> #include \n>>>> #include \n>>>> @@ -328,14 +329,17 @@ done:\n>>>> */\n>>>> \n>>>> /**\n>>>> - * \\brief Return the MediaEntity with name \\a name\n>>>> - * \\param[in] name The entity name\n>>>> - * \\return The entity with \\a name, or nullptr if no such entity is found\n>>>> + * \\brief Return the MediaEntity with name matching the regex \\a name\n>>> \"whose name matches\" ?\n>> Sure\n>>\n>>>> + * \\param[in] name Regex to match against the entity name\n>>>> + * \\return The entity with name matching \\a name, or nullptr if no such entity\n>>>> + * is found\n>>> Entity names are unique, but with regex that's not the case anymore. If\n>>> multiple entities match the regex, the behaviour of this function will\n>>> not be predictable. Is that a concern ? It should at least be properly\n>>> documented.\n>> I guess it might be...perhaps this should count the returned matches and complain heavily if the\n>> answer is >1?\n> Is that the most appropriate behaviour for the use cases you envision ?\n> What are those use cases actually ?\nIn the specific scenario I'm encountering we need to pick out the entity called something like \ncru-ip-16000000.cru0 depending on the specific connector that you've plugged the camera in to.  The \nreturned entity is used to create a V4L2Subdevice instance and call setFormat() at configuration \ntime. We definitely need the right subdevice; if the match finds multiple and so can't guarantee the \nright one I think that complaining and returning a nullptr is probably the most appropriate thing to \ndo yes. Follow up from that would have to be fixing the matching string in libcamera to return a \nunique entity I suppose...ideally of course the kernel would never present this problem to us, but \nit has and I assume that the entity names are counted as part of the kernel's uAPI.\n>\n>>>> */\n>>>> MediaEntity *MediaDevice::getEntityByName(const std::string &name) const\n>>>> {\n>>>> +\tstd::regex name_regex(name);\n>>>> +\n>>>> \tfor (MediaEntity *e : entities_)\n>>>> -\t\tif (e->name() == name)\n>>>> +\t\tif (std::regex_search(e->name(), name_regex))\n>>>> \t\t\treturn e;\n>>>> \n>>>> \treturn nullptr;\n>>>> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp\n>>>> index 33279654..4868785d 100644\n>>>> --- a/src/libcamera/v4l2_subdevice.cpp\n>>>> +++ b/src/libcamera/v4l2_subdevice.cpp\n>>>> @@ -1748,10 +1748,10 @@ const std::string &V4L2Subdevice::model()\n>>>> */\n>>>> \n>>>> /**\n>>>> - * \\brief Create a new video subdevice instance from \\a entity in media device\n>>>> + * \\brief Create a new video subdevice instance from an entity in media device\n>>> \"\\a entity\" refers to the entity parameter.\n>> I think I changed that because the horrible regex string wouldn't necessarily be easily read as the\n>> entity anymore...but perhaps that's too persnickity\n>>\n>>>> * \\a media\n>>>> * \\param[in] media The media device where the entity is registered\n>>>> - * \\param[in] entity The media entity name\n>>>> + * \\param[in] entity A regex that will match media entity name\n>>>> *\n>>>> * \\return A newly created V4L2Subdevice on success, nullptr otherwise\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 E9B15BE175\n\tfor ;\n\tTue, 15 Jul 2025 14:09:22 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D34FF68F5E;\n\tTue, 15 Jul 2025 16:09:21 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 42F186186B\n\tfor ;\n\tTue, 15 Jul 2025 16:09:20 +0200 (CEST)","from [192.168.0.43]\n\t(cpc141996-chfd3-2-0-cust928.12-3.cable.virginm.net [86.13.91.161])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 84583735;\n\tTue, 15 Jul 2025 16:08:47 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; 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