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Date:   Fri, 19 Mar 2021 09:24:35 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     "Enrico Weigelt, metux IT consult" <lkml@metux.net>,
        Jie Deng <jie.deng@intel.com>,
        Linux I2C <linux-i2c@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Wolfram Sang <wsa@kernel.org>,
        Jason Wang <jasowang@redhat.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        conghui.chen@intel.com, kblaiech@mellanox.com,
        jarkko.nikula@linux.intel.com,
        Sergey Semin <Sergey.Semin@baikalelectronics.ru>,
        Mike Rapoport <rppt@kernel.org>, loic.poulain@linaro.org,
        Tali Perry <tali.perry1@gmail.com>,
        Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        yu1.wang@intel.com, shuo.a.liu@intel.com,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
Message-ID: <20210319035435.a4reve77hnvjdzwk@vireshk-i7>
References: <c193b92d8d22ba439bb1b260d26d4b76f57d4840.1615889867.git.jie.deng@intel.com>
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On 18-03-21, 15:52, Arnd Bergmann wrote:
> Allowing multiple virtio-i2c controllers in one system, and multiple i2c
> devices attached to each controller is clearly something that has to work.

Good.

> I don't actually see a limitation though. Viresh, what is the problem
> you see for having multiple controllers?

I thought this would be a problem in that case as we are using the global
virtio_adapter here.

+       vi->adap = &virtio_adapter;
+       i2c_set_adapdata(vi->adap, vi);

Multiple calls to probe() will end up updating the same pointer inside adap.

+       vi->adap->dev.parent = &vdev->dev;

Same here, overwrite.

+       /* Setup ACPI node for controlled devices which will be probed through ACPI */
+       ACPI_COMPANION_SET(&vi->adap->dev, ACPI_COMPANION(pdev));
+       vi->adap->timeout = HZ / 10;

These may be fine, but still not ideal I believe.

+       ret = i2c_add_adapter(vi->adap);
i
This should be a problem as well, we must be adding this to some sort of list,
doing some RPM stuff, etc ?

Jie, the solution is to allocate memory for adap at runtime in probe and remove
the virtio_adapter structure completely.

-- 
viresh