linux-kernel - Re: [PATCH v2 1/2] driver core: platform: Initialize dma

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Date:   Wed, 22 Apr 2020 11:41:45 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Robin Murphy <robin.murphy@....com>,
        Vinod Koul <vkoul@...nel.org>, Haibo Chen <haibo.chen@....com>,
        Ludovic Barre <ludovic.barre@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        dmaengine@...r.kernel.org, "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] driver core: platform: Initialize dma_parms for
 platform devices

On Tue, Mar 31, 2020 at 8:38 PM Ulf Hansson <ulf.hansson@...aro.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@....de>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>

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