Re: [PATCH 09/15] device core: Add ability to handle multiple dma offsets - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jim Quinlan <james.quinlan@broadcom.com>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE"
	<devicetree@vger.kernel.org>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Saravana Kannan <saravanak@google.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Frank Rowand <frowand.list@gmail.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	open list <linux-kernel@vger.kernel.org>,
	"open list:DMA MAPPING HELPERS"
	<iommu@lists.linux-foundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: Re: [PATCH 09/15] device core: Add ability to handle multiple dma offsets
Date: Wed, 20 May 2020 07:43:49 +0200	[thread overview]
Message-ID: <20200520054349.GB2180554@kroah.com> (raw)
In-Reply-To: <20200519203419.12369-10-james.quinlan@broadcom.com>

On Tue, May 19, 2020 at 04:34:07PM -0400, Jim Quinlan wrote:
> diff --git a/include/linux/device.h b/include/linux/device.h
> index ac8e37cd716a..6cd916860b5f 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -493,6 +493,8 @@ struct dev_links_info {
>   * @bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller
>   *		DMA limit than the device itself supports.
>   * @dma_pfn_offset: offset of DMA memory range relatively of RAM
> + * @dma_map:	Like dma_pfn_offset but used when there are multiple
> + *		pfn offsets for multiple dma-ranges.
>   * @dma_parms:	A low level driver may set these to teach IOMMU code about
>   * 		segment limitations.
>   * @dma_pools:	Dma pools (if dma'ble device).
> @@ -578,7 +580,12 @@ struct device {
>  					     allocations such descriptors. */
>  	u64		bus_dma_limit;	/* upstream dma constraint */
>  	unsigned long	dma_pfn_offset;
> -
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +	const void *dma_offset_map;	/* Like dma_pfn_offset, but for
> +					 * the unlikely case of multiple
> +					 * offsets. If non-null, dma_pfn_offset
> +					 * will be 0. */
> +#endif
>  	struct device_dma_parameters *dma_parms;
>  
>  	struct list_head	dma_pools;	/* dma pools (if dma'ble) */

I'll defer to Christoph here, but I thought we were trying to get rid of
stuff like this from struct device, not add new things to it for dma
apis.  And why is it a void *?

thanks,

greg k-h
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