linux-kernel - Re: next take at setting up a dma mask by default for platform devices

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Date:   Thu, 15 Aug 2019 15:23:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Gavin Li <git@...gavinli.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Geoff Levand <geoff@...radead.org>,
        Michal Simek <michal.simek@...inx.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Olav Kongas <ok@...ecdesign.ee>,
        Tony Prisk <linux@...sktech.co.nz>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Bin Liu <b-liu@...com>, linux-arm-kernel@...ts.infradead.org,
        linux-usb@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: next take at setting up a dma mask by default for platform
 devices

On Sun, Aug 11, 2019 at 10:05:14AM +0200, Christoph Hellwig wrote:
> Hi all,
> 
> this is another attempt to make sure the dma_mask pointer is always
> initialized for platform devices.  Not doing so lead to lots of
> boilerplate code, and makes platform devices different from all our
> major busses like PCI where we always set up a dma_mask.  In the long
> run this should also help to eventually make dma_mask a scalar value
> instead of a pointer and remove even more cruft.
> 
> The bigger blocker for this last time was the fact that the usb
> subsystem uses the presence or lack of a dma_mask to check if the core
> should do dma mapping for the driver, which is highly unusual.  So we
> fix this first.  Note that this has some overlap with the pending
> desire to use the proper dma_mmap_coherent helper for mapping usb
> buffers.  The first two patches from this series should probably
> go into 5.3 and then uses as the basis for the decision to use
> dma_mmap_coherent.

I've taken the first 2 patches for 5.3-final.  Given that patch 3 needs
to be fixed, I'll wait for a respin of these before considering them.

thanks,

greg k-h