From: Vivek Gautam <vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> To: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org> Cc: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>, "Rafael J. Wysocki" <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org>, open list <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "list-Y9sIeH5OGRo@public.gmane.org:IOMMU DRIVERS" <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, robh+dt <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, linux-arm-msm <linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> Subject: Re: [PATCH v9 1/5] driver core: Find an existing link between two devices Date: Tue, 13 Mar 2018 20:09:09 +0530 [thread overview] Message-ID: <CAFp+6iGaAbXOj2hXf12oQzi57J2DX+13f86oprOezyF8rkeyNg@mail.gmail.com> (raw) In-Reply-To: <4eaf2006-ea68-d9e9-a0db-89acec0ea299-5wv7dgnIgG8@public.gmane.org> Hi Robin, On Tue, Mar 13, 2018 at 6:19 PM, Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org> wrote: > On 13/03/18 09:55, Vivek Gautam wrote: >> >> On Tue, Mar 13, 2018 at 3:10 PM, Rafael J. Wysocki <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> >> wrote: >>> >>> On Tuesday, March 13, 2018 9:55:30 AM CET Vivek Gautam wrote: >>>> >>>> The lists managing the device-links can be traversed to >>>> find the link between two devices. The device_link_add() APIs >>>> does traverse these lists to check if there's already a link >>>> setup between the two devices. >>>> So, add a new APIs, device_link_find(), to find an existing >>>> device link between two devices - suppliers and consumers. >>>> >>>> Signed-off-by: Vivek Gautam <vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> >>>> Cc: Rafael J. Wysocki <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> >>>> Cc: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> >>>> --- >>>> >>>> * New patch added to this series. >>>> >>>> drivers/base/core.c | 30 +++++++++++++++++++++++++++--- >>>> include/linux/device.h | 2 ++ >>>> 2 files changed, 29 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/base/core.c b/drivers/base/core.c >>>> index 5847364f25d9..e8c9774e4ba2 100644 >>>> --- a/drivers/base/core.c >>>> +++ b/drivers/base/core.c >>>> @@ -144,6 +144,30 @@ static int device_reorder_to_tail(struct device >>>> *dev, void *not_used) >>>> return 0; >>>> } >>>> >>>> +/** >>>> + * device_link_find - find any existing link between two devices. >>>> + * @consumer: Consumer end of the link. >>>> + * @supplier: Supplier end of the link. >>>> + * >>>> + * Returns pointer to the existing link between a supplier and >>>> + * and consumer devices, or NULL if no link exists. >>>> + */ >>>> +struct device_link *device_link_find(struct device *consumer, >>>> + struct device *supplier) >>>> +{ >>>> + struct device_link *link = NULL; >>>> + >>>> + if (!consumer || !supplier) >>>> + return NULL; >>>> + >>>> + list_for_each_entry(link, &supplier->links.consumers, s_node) >>>> + if (link->consumer == consumer) >>>> + break; >>>> + >>> >>> >>> Any mutual exclusion? >>> >>> Or is the caller expected to take care of it? And if so, then how? >> >> >> I think it's better that we take care of lock here in the code rather >> than depending >> on the caller. >> But i can't take device_links_write_lock() since device_link_add() >> already takes that. > > > Well, the normal pattern is to break out the internal helper function as-is, > then add a public wrapper which validates inputs, handles locking, etc., > equivalently to existing caller(s). See what device_link_del() and others > do, e.g.: > > static struct device_link *__device_link_find(struct device *consumer, > struct device *supplier) > { > list_for_each_entry(link, &supplier->links.consumers, s_node) > if (link->consumer == consumer) > return link; > return NULL; > } > > struct device_link *device_link_find(struct device *consumer, > struct device *supplier) > { > struct device_link *link; > > if (!consumer || !supplier) > return NULL; > > device_links_write_lock(); > link = __device_link_find(consumer, supplier); > device_links_write_unlock(); > return link; > } > > where device_link_add() would call __device_link_find() directly. Right, I understand it now. Thanks for detailed explanation. regards Vivek > > However, as Tomasz points out (and I hadn't really considered), if the only > reasonable thing to with a link once you've found it is to delete it, then > in terms of the public API it may well make more sense to just implement > something like a device_link_remove() which does both in one go. > > Robin. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: Vivek Gautam <vivek.gautam@codeaurora.org> To: Robin Murphy <robin.murphy@arm.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>, "list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>, Joerg Roedel <joro@8bytes.org>, "robh+dt" <robh+dt@kernel.org>, devicetree@vger.kernel.org, open list <linux-kernel@vger.kernel.org>, Mark Rutland <mark.rutland@arm.com>, Will Deacon <will.deacon@arm.com>, Rob Clark <robdclark@gmail.com>, Tomasz Figa <tfiga@chromium.org>, Sricharan R <sricharan@codeaurora.org>, Marek Szyprowski <m.szyprowski@samsung.com>, Archit Taneja <architt@codeaurora.org>, linux-arm-msm <linux-arm-msm@vger.kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org> Subject: Re: [PATCH v9 1/5] driver core: Find an existing link between two devices Date: Tue, 13 Mar 2018 20:09:09 +0530 [thread overview] Message-ID: <CAFp+6iGaAbXOj2hXf12oQzi57J2DX+13f86oprOezyF8rkeyNg@mail.gmail.com> (raw) In-Reply-To: <4eaf2006-ea68-d9e9-a0db-89acec0ea299@arm.com> Hi Robin, On Tue, Mar 13, 2018 at 6:19 PM, Robin Murphy <robin.murphy@arm.com> wrote: > On 13/03/18 09:55, Vivek Gautam wrote: >> >> On Tue, Mar 13, 2018 at 3:10 PM, Rafael J. Wysocki <rjw@rjwysocki.net> >> wrote: >>> >>> On Tuesday, March 13, 2018 9:55:30 AM CET Vivek Gautam wrote: >>>> >>>> The lists managing the device-links can be traversed to >>>> find the link between two devices. The device_link_add() APIs >>>> does traverse these lists to check if there's already a link >>>> setup between the two devices. >>>> So, add a new APIs, device_link_find(), to find an existing >>>> device link between two devices - suppliers and consumers. >>>> >>>> Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org> >>>> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> >>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>>> --- >>>> >>>> * New patch added to this series. >>>> >>>> drivers/base/core.c | 30 +++++++++++++++++++++++++++--- >>>> include/linux/device.h | 2 ++ >>>> 2 files changed, 29 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/base/core.c b/drivers/base/core.c >>>> index 5847364f25d9..e8c9774e4ba2 100644 >>>> --- a/drivers/base/core.c >>>> +++ b/drivers/base/core.c >>>> @@ -144,6 +144,30 @@ static int device_reorder_to_tail(struct device >>>> *dev, void *not_used) >>>> return 0; >>>> } >>>> >>>> +/** >>>> + * device_link_find - find any existing link between two devices. >>>> + * @consumer: Consumer end of the link. >>>> + * @supplier: Supplier end of the link. >>>> + * >>>> + * Returns pointer to the existing link between a supplier and >>>> + * and consumer devices, or NULL if no link exists. >>>> + */ >>>> +struct device_link *device_link_find(struct device *consumer, >>>> + struct device *supplier) >>>> +{ >>>> + struct device_link *link = NULL; >>>> + >>>> + if (!consumer || !supplier) >>>> + return NULL; >>>> + >>>> + list_for_each_entry(link, &supplier->links.consumers, s_node) >>>> + if (link->consumer == consumer) >>>> + break; >>>> + >>> >>> >>> Any mutual exclusion? >>> >>> Or is the caller expected to take care of it? And if so, then how? >> >> >> I think it's better that we take care of lock here in the code rather >> than depending >> on the caller. >> But i can't take device_links_write_lock() since device_link_add() >> already takes that. > > > Well, the normal pattern is to break out the internal helper function as-is, > then add a public wrapper which validates inputs, handles locking, etc., > equivalently to existing caller(s). See what device_link_del() and others > do, e.g.: > > static struct device_link *__device_link_find(struct device *consumer, > struct device *supplier) > { > list_for_each_entry(link, &supplier->links.consumers, s_node) > if (link->consumer == consumer) > return link; > return NULL; > } > > struct device_link *device_link_find(struct device *consumer, > struct device *supplier) > { > struct device_link *link; > > if (!consumer || !supplier) > return NULL; > > device_links_write_lock(); > link = __device_link_find(consumer, supplier); > device_links_write_unlock(); > return link; > } > > where device_link_add() would call __device_link_find() directly. Right, I understand it now. Thanks for detailed explanation. regards Vivek > > However, as Tomasz points out (and I hadn't really considered), if the only > reasonable thing to with a link once you've found it is to delete it, then > in terms of the public API it may well make more sense to just implement > something like a device_link_remove() which does both in one go. > > Robin. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2018-03-13 14:39 UTC|newest] Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-13 8:55 [PATCH v9 0/5] iommu/arm-smmu: Add runtime pm/sleep support Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam [not found] ` <20180313085534.11650-1-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-03-13 8:55 ` [PATCH v9 1/5] driver core: Find an existing link between two devices Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam 2018-03-13 9:40 ` Rafael J. Wysocki [not found] ` <8903307.QazHKW0JrR-yvgW3jdyMHm1GS7QM15AGw@public.gmane.org> 2018-03-13 9:55 ` Vivek Gautam 2018-03-13 9:55 ` Vivek Gautam [not found] ` <CAFp+6iE=0PD6fZZVd+bC1Z95Lkt=X-F4YOXz8EtdiXL=jsC1RA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-13 12:49 ` Robin Murphy 2018-03-13 12:49 ` Robin Murphy [not found] ` <4eaf2006-ea68-d9e9-a0db-89acec0ea299-5wv7dgnIgG8@public.gmane.org> 2018-03-13 14:39 ` Vivek Gautam [this message] 2018-03-13 14:39 ` Vivek Gautam [not found] ` <20180313085534.11650-2-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-03-13 9:58 ` Vivek Gautam 2018-03-13 9:58 ` Vivek Gautam 2018-03-13 10:15 ` Tomasz Figa [not found] ` <CAAFQd5DXvnjaFw4Ct1Xn90nQZ4F4dLtov0ymG-tycQt5oLNpiQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-13 10:34 ` Vivek Gautam 2018-03-13 10:34 ` Vivek Gautam 2018-03-13 11:23 ` Tomasz Figa [not found] ` <CAAFQd5A5Rj1KAZjUc5ZUKuKnbkA5Q6aLw9z0H3_kfyBQOOF-gw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-14 11:12 ` Rafael J. Wysocki 2018-03-14 11:12 ` Rafael J. Wysocki [not found] ` <2217404.A2W3Iek6du-yvgW3jdyMHm1GS7QM15AGw@public.gmane.org> 2018-03-14 11:50 ` Tomasz Figa 2018-03-14 11:50 ` Tomasz Figa [not found] ` <CAAFQd5CQXY0Efv+2MC1kTVW5q4eZjJ=gwVaR-LA=3agnSSHzUw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-14 11:57 ` Rafael J. Wysocki 2018-03-14 11:57 ` Rafael J. Wysocki [not found] ` <2705105.V6KYPvoJqj-yvgW3jdyMHm1GS7QM15AGw@public.gmane.org> 2018-03-14 12:14 ` Robin Murphy 2018-03-14 12:14 ` Robin Murphy 2018-03-14 12:27 ` Lukas Wunner [not found] ` <20180314122759.GB19651-JFq808J9C/izQB+pC5nmwQ@public.gmane.org> 2018-03-20 7:56 ` Vivek Gautam 2018-03-20 7:56 ` Vivek Gautam 2018-03-14 12:23 ` Lukas Wunner 2018-03-13 8:55 ` [PATCH v9 2/5] iommu/arm-smmu: Add pm_runtime/sleep ops Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam 2018-03-13 8:55 ` [PATCH v9 3/5] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam [not found] ` <20180313085534.11650-4-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-03-14 17:46 ` Robin Murphy 2018-03-14 17:46 ` Robin Murphy [not found] ` <77ed3675-0af0-b36a-5f76-b920d7a4c8e0-5wv7dgnIgG8@public.gmane.org> 2018-03-15 7:17 ` Tomasz Figa 2018-03-15 7:17 ` Tomasz Figa 2018-03-20 9:49 ` Vivek Gautam 2018-03-20 9:49 ` Vivek Gautam 2018-03-13 8:55 ` [PATCH v9 4/5] iommu/arm-smmu: Add the device_link between masters and smmu Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam [not found] ` <20180313085534.11650-5-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-03-14 17:50 ` Robin Murphy 2018-03-14 17:50 ` Robin Murphy [not found] ` <8b427ea2-5c13-4712-13d1-e4c1aed0779e-5wv7dgnIgG8@public.gmane.org> 2018-03-15 6:18 ` Tomasz Figa 2018-03-15 6:18 ` Tomasz Figa [not found] ` <CAAFQd5AqERQMLsJNLAsVXox79kZ+ZtpCUuMSutn70FGK-3Q7vw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-15 10:44 ` Robin Murphy 2018-03-15 10:44 ` Robin Murphy 2018-03-15 8:57 ` Vivek Gautam 2018-03-15 8:57 ` Vivek Gautam [not found] ` <CAFp+6iEFDXKdS_mTgrrpCX2isMAT3XJifRV0FYxV+PFpVGV=2w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-03-15 11:12 ` Robin Murphy 2018-03-15 11:12 ` Robin Murphy 2018-03-13 8:55 ` [PATCH v9 5/5] iommu/arm-smmu: Add support for qcom,smmu-v2 variant Vivek Gautam 2018-03-13 8:55 ` Vivek Gautam [not found] ` <61d30fff-1bf8-d2c1-bbe9-f93de836ae77@huawei.com> [not found] ` <7d5af071-ef98-8461-3ce9-e84fc0b3956a@codeaurora.org> [not found] ` <7d5af071-ef98-8461-3ce9-e84fc0b3956a-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-03-28 6:11 ` Yisheng Xie 2018-03-28 6:11 ` Yisheng Xie [not found] ` <d97872fe-5e8e-cc27-e385-64cea8ea2458-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> 2018-04-10 13:14 ` [PATCH v9 5/5] iommu/arm-smmu: Add support for qcom, smmu-v2 variant Tomasz Figa 2018-04-10 13:14 ` [PATCH v9 5/5] iommu/arm-smmu: Add support for qcom,smmu-v2 variant Tomasz Figa [not found] ` <CAAFQd5Cj3qaqt8ACabZwN4ZKaNbF9N9suGVaOKD8-kNxgfeeVA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-04-11 1:22 ` Yisheng Xie 2018-04-11 1:22 ` Yisheng Xie [not found] ` <65a57964-805b-3a38-71a2-0c383af30539-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> 2018-04-11 5:15 ` Vivek Gautam 2018-04-11 5:15 ` Vivek Gautam [not found] ` <ff1c730f-0009-58e5-cf4a-45fe9ab93d1e-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-04-12 1:55 ` Yisheng Xie 2018-04-12 1:55 ` Yisheng Xie
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=CAFp+6iGaAbXOj2hXf12oQzi57J2DX+13f86oprOezyF8rkeyNg@mail.gmail.com \ --to=vivek.gautam-sgv2jx0feol9jmxxk+q4oq@public.gmane.org \ --cc=devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org \ --cc=iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \ --cc=linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=mark.rutland-5wv7dgnIgG8@public.gmane.org \ --cc=rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org \ --cc=robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org \ --cc=robin.murphy-5wv7dgnIgG8@public.gmane.org \ --cc=will.deacon-5wv7dgnIgG8@public.gmane.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.