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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 22 Apr 2020 11:41:45 +0200
Message-ID: <CAK8P3a0Nqvho82529dAi6oZhh0PgjiRfj=NLdNkkMfZ6Tw25iw@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for
 platform devices
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Russell King <linux@armlinux.org.uk>,
        Linus Walleij <linus.walleij@linaro.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Vinod Koul <vkoul@kernel.org>, Haibo Chen <haibo.chen@nxp.com>,
        Ludovic Barre <ludovic.barre@st.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        dmaengine@vger.kernel.org, "# 3.4.x" <stable@vger.kernel.org>
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On Tue, Mar 31, 2020 at 8:38 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> It's currently the platform driver's responsibility to initialize the
> pointer, dma_parms, for its corresponding struct device. The benefit with
> this approach allows us to avoid the initialization and to not waste memory
> for the struct device_dma_parameters, as this can be decided on a case by
> case basis.
>
> However, it has turned out that this approach is not very practical.  Not
> only does it lead to open coding, but also to real errors. In principle
> callers of dma_set_max_seg_size() doesn't check the error code, but just
> assumes it succeeds.
>
> For these reasons, let's do the initialization from the common platform bus
> at the device registration point. This also follows the way the PCI devices
> are being managed, see pci_device_add().
>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>