linux-kernel - [PATCH 0/2] amba/platform: Initialize dma

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Date:   Wed, 25 Mar 2020 12:34:05 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vinod Koul <vkoul@...nel.org>, Haibo Chen <haibo.chen@....com>,
        Ludovic Barre <ludovic.barre@...com>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 0/2] amba/platform: Initialize dma_parms at the bus level

It's currently the amba/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, this series initializes the dma_parms from the amba/platform
bus at the device registration point. This also follows the way the PCI devices
are being managed, see pci_device_add().

If it turns out that this is an acceptable solution, we probably also want the
changes for stable, but I am not sure if it applies without conflicts.

The series is based on v5.6-rc7.

Kind regards
Ulf Hansson

Ulf Hansson (2):
  driver core: platform: Initialize dma_parms for platform devices
  amba: Initialize dma_parms for amba devices

 drivers/amba/bus.c              | 2 ++
 drivers/base/platform.c         | 1 +
 include/linux/amba/bus.h        | 1 +
 include/linux/platform_device.h | 1 +
 4 files changed, 5 insertions(+)

-- 
2.20.1