Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v4 1/7] interconnect: Add generic on-chip interconnect API
From:   Georgi Djakov <georgi.djakov@linaro.org>
To:     Evan Green <evgreen@chromium.org>
Cc:     linux-pm@vger.kernel.org, gregkh@linuxfoundation.org,
        rjw@rjwysocki.net, robh+dt@kernel.org,
        Michael Turquette <mturquette@baylibre.com>,
        khilman@baylibre.com, vincent.guittot@linaro.org,
        skannan@codeaurora.org,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        amit.kucheria@linaro.org, seansw@qti.qualcomm.com,
        davidai@quicinc.com, mark.rutland@arm.com,
        lorenzo.pieralisi@arm.com, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org
References: <20180309210958.16672-1-georgi.djakov@linaro.org>
 <20180309210958.16672-2-georgi.djakov@linaro.org>
 <CAE=gft76VpU1mXgNPK9-XTj6WoLHj-_SxAGuV-bUSNYVpfSn6w@mail.gmail.com>
 <43fedb5b-f4a5-8362-d0a2-534b85473bc1@linaro.org>
Openpgp: preference=signencrypt
Autocrypt: addr=georgi.djakov@linaro.org; prefer-encrypt=mutual; keydata=
 xsFNBFjTuRcBEACyAOVzghvyN19Sa/Nit4LPBWkICi5W20p6bwiZvdjhtuh50H5q4ktyxJtp
 1+s8dMSa/j58hAWhrc2SNL3fttOCo+MM1bQWwe8uMBQJP4swgXf5ZUYkSssQlXxGKqBSbWLB
 uFHOOBTzaQBaNgsdXo+mQ1h8UCgM0zQOmbs2ort8aHnH2i65oLs5/Xgv/Qivde/FcFtvEFaL
 0TZ7odM67u+M32VetH5nBVPESmnEDjRBPw/DOPhFBPXtal53ZFiiRr6Bm1qKVu3dOEYXHHDt
 nF13gB+vBZ6x5pjl02NUEucSHQiuCc2Aaavo6xnuBc3lnd4z/xk6GLBqFP3P/eJ56eJv4d0B
 0LLgQ7c1T3fU4/5NDRRCnyk6HJ5+HSxD4KVuluj0jnXW4CKzFkKaTxOp7jE6ZD/9Sh74DM8v
 etN8uwDjtYsM07I3Szlh/I+iThxe/4zVtUQsvgXjwuoOOBWWc4m4KKg+W4zm8bSCqrd1DUgL
 f67WiEZgvN7tPXEzi84zT1PiUOM98dOnmREIamSpKOKFereIrKX2IcnZn8jyycE12zMkk+Sc
 ASMfXhfywB0tXRNmzsywdxQFcJ6jblPNxscnGMh2VlY2rezmqJdcK4G4Lprkc0jOHotV/6oJ
 mj9h95Ouvbq5TDHx+ERn8uytPygDBR67kNHs18LkvrEex/Z1cQARAQABzShHZW9yZ2kgRGph
 a292IDxnZW9yZ2kuZGpha292QGxpbmFyby5vcmc+wsF+BBMBAgAoBQJY07kXAhsDBQkHhM4A
 BgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRCyi/eZcnWWUuvsD/4miikUeAO6fU2Xy3fT
 l7RUCeb2Uuh1/nxYoE1vtXcow6SyAvIVTD32kHXucJJfYy2zFzptWpvD6Sa0Sc58qe4iLY4j
 M54ugOYK7XeRKkQHFqqR2T3g/toVG1BOLS2atooXEU+8OFbpLkBXbIdItqJ1M1SEw8YgKmmr
 JlLAaKMq3hMb5bDQx9erq7PqEKOB/Va0nNu17IL58q+Q5Om7S1x54Oj6LiG/9kNOxQTklOQZ
 t61oW1Ewjbl325fW0/Lk0QzmfLCrmGXXiedFEMRLCJbVImXVKdIt/Ubk6SAAUrA5dFVNBzm2
 L8r+HxJcfDeEpdOZJzuwRyFnH96u1Xz+7X2V26zMU6Wl2+lhvr2Tj7spxjppR+nuFiybQq7k
 MIwyEF0mb75RLhW33sdGStCZ/nBsXIGAUS7OBj+a5fm47vQKv6ekg60oRTHWysFSJm1mlRyq
 exhI6GwUo5GM/vE36rIPSJFRRgkt6nynoba/1c4VXxfhok2rkP0x3CApJ5RimbvITTnINY0o
 CU6f1ng1I0A1UTi2YcLjFq/gmCdOHExT4huywfu1DDf0p1xDyPA1FJaii/gJ32bBP3zK53hM
 dj5S7miqN7F6ZpvGSGXgahQzkGyYpBR5pda0m0k8drV2IQn+0W8Qwh4XZ6/YdfI81+xyFlXc
 CJjljqsMCJW6PdgEH87BTQRY07kXARAAvupGd4Jdd8zRRiF+jMpv6ZGz8L55Di1fl1YRth6m
 lIxYTLwGf0/p0oDLIRldKswena3fbWh5bbTMkJmRiOQ/hffhPSNSyyh+WQeLY2kzl6geiHxD
 zbw37e2hd3rWAEfVFEXOLnmenaUeJFyhA3Wd8OLdRMuoV+RaLhNfeHctiEn1YGy2gLCq4VNb
 4Wj5hEzABGO7+LZ14hdw3hJIEGKtQC65Jh/vTayGD+qdwedhINnIqslk9tCQ33a+jPrCjXLW
 X29rcgqigzsLHH7iVHWA9R5Aq7pCy5hSFsl4NBn1uV6UHlyOBUuiHBDVwTIAUnZ4S8EQiwgv
 WQxEkXEWLM850V+G6R593yZndTr3yydPgYv0xEDACd6GcNLR/x8mawmHKzNmnRJoOh6Rkfw2
 fSiVGesGo83+iYq0NZASrXHAjWgtZXO1YwjW9gCQ2jYu9RGuQM8zIPY1VDpQ6wJtjO/KaOLm
 NehSR2R6tgBJK7XD9it79LdbPKDKoFSqxaAvXwWgXBj0Oz+Y0BqfClnAbxx3kYlSwfPHDFYc
 R/ppSgnbR5j0Rjz/N6Lua3S42MDhQGoTlVkgAi1btbdV3qpFE6jglJsJUDlqnEnwf03EgjdJ
 6KEh0z57lyVcy5F/EUKfTAMZweBnkPo+BF2LBYn3Qd+CS6haZAWaG7vzVJu4W/mPQzsAEQEA
 AcLBZQQYAQIADwUCWNO5FwIbDAUJB4TOAAAKCRCyi/eZcnWWUhlHD/0VE/2x6lKh2FGP+QHH
 UTKmiiwtMurYKJsSJlQx0T+j/1f+zYkY3MDX+gXa0d0xb4eFv8WNlEjkcpSPFr+pQ7CiAI33
 99kAVMQEip/MwoTYvM9NXSMTpyRJ/asnLeqa0WU6l6Z9mQ41lLzPFBAJ21/ddT4xeBDv0dxM
 GqaH2C6bSnJkhSfSja9OxBe+F6LIAZgCFzlogbmSWmUdLBg+sh3K6aiBDAdZPUMvGHzHK3fj
 gHK4GqGCFK76bFrHQYgiBOrcR4GDklj4Gk9osIfdXIAkBvRGw8zg1zzUYwMYk+A6v40gBn00
 OOB13qJe9zyKpReWMAhg7BYPBKIm/qSr82aIQc4+FlDX2Ot6T/4tGUDr9MAHaBKFtVyIqXBO
 xOf0vQEokkUGRKWBE0uA3zFVRfLiT6NUjDQ0vdphTnsdA7h01MliZLQ2lLL2Mt5lsqU+6sup
 Tfql1omgEpjnFsPsyFebzcKGbdEr6vySGa3Cof+miX06hQXKe99a5+eHNhtZJcMAIO89wZmj
 7ayYJIXFqjl/X0KBcCbiAl4vbdBw1bqFnO4zd1lMXKVoa29UHqby4MPbQhjWNVv9kqp8A39+
 E9xw890l1xdERkjVKX6IEJu2hf7X3MMl9tOjBK6MvdOUxvh1bNNmXh7OlBL1MpJYY/ydIm3B
 KEmKjLDvB0pePJkdTw==
Message-ID: <c98d2ee2-c4fa-eb35-e6ae-f6d9c91ffe6c@linaro.org>
Date:   Wed, 6 Jun 2018 21:09:24 +0300
MIME-Version: 1.0
In-Reply-To: <43fedb5b-f4a5-8362-d0a2-534b85473bc1@linaro.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Evan,

On 06/06/2018 05:59 PM, Georgi Djakov wrote:
>>> +
>>> +/**
>>> + * icc_node_create() - create a node
>>> + * @id: node id
>>> + *
>>> + * Return: icc_node pointer on success, or ERR_PTR() on error
>>> + */
>>> +struct icc_node *icc_node_create(int id)
>>> +{
>>> +       struct icc_node *node;
>>> +
>>> +       /* check if node already exists */
>>> +       node = node_find(id);
>>> +       if (node)
>>> +               return node;
>>
>> This is probably going to do more harm than good once icc_node_delete comes
>> in, since it almost certainly indicates a programmer error or ID collision,
>> and will likely result in a double free. We should probably fail with
>> EEXIST instead.
> 
> In the current approach we create the nodes one by one, and the linked
> nodes are created when they are referenced. The other way around would
> be to create first all the nodes and then populate the links to avoid
> the "chicken and egg" problem.
> 

Just to elaborate a bit more on that: We can't actually register all the
nodes in advance, as we might have multiple interconnect providers
probing in different order. Each provider may have nodes linking to
nodes belonging to other providers (not probed yet). That's why we
create the nodes on the first reference and then, when the actual
provider driver is probed, the rest of the node data is filled.

Thanks,
Georgi