linux-kernel - RE: [PATCH 1/2] device: Stop requiring that struct device is embedded in struct pci

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Message-ID: <VI1PR0502MB3008D3B38ED2F3694E100E5ED12F0@VI1PR0502MB3008.eurprd05.prod.outlook.com>
Date:   Tue, 7 Mar 2017 02:41:32 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Bart Van Assche <bart.vanassche@...disk.com>,
        Doug Ledford <dledford@...hat.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sebastian Ott <sebott@...ux.vnet.ibm.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>
Subject: RE: [PATCH 1/2] device: Stop requiring that struct device is embedded
 in struct pci_dev

Hi Bart,

> -----Original Message-----
> From: linux-rdma-owner@...r.kernel.org [mailto:linux-rdma-
> owner@...r.kernel.org] On Behalf Of Bart Van Assche
> Sent: Monday, March 6, 2017 6:36 PM
> To: Doug Ledford <dledford@...hat.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Sebastian Ott
> <sebott@...ux.vnet.ibm.com>; Parav Pandit <parav@...lanox.com>; linux-
> rdma@...r.kernel.org; linux-kernel@...r.kernel.org; Bart Van Assche
> <bart.vanassche@...disk.com>; Bjorn Helgaas <bhelgaas@...gle.com>;
> Benjamin Herrenschmidt <benh@...nel.crashing.org>; David Woodhouse
> <dwmw2@...radead.org>; H . Peter Anvin <hpa@...or.com>; Ingo Molnar
> <mingo@...hat.com>; Russell King <linux@...linux.org.uk>
> Subject: [PATCH 1/2] device: Stop requiring that struct device is embedded in
> struct pci_dev
> 
> The dma mapping operations of several architectures and also of several I/O
> MMU implementations need to translate a struct device pointer into a struct
> pci_dev pointer. This translation is performed by to_pci_dev(). That macro
> assumes that struct device is embedded in struct pci_dev. However, that is
> not the case for the device structure in struct ib_device. Since that device
> structure is passed to DMA mapping operations since kernel v4.11-rc1,
> introduce a pointer in struct device to make the translation from struct
> device into struct pci_dev more flexible.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@...disk.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: David Woodhouse <dwmw2@...radead.org>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Russell King <linux@...linux.org.uk>
> ---
>  drivers/pci/probe.c    | 1 +
>  include/linux/device.h | 5 +++++
>  include/linux/pci.h    | 5 ++++-
>  3 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/device.h b/include/linux/device.h index
> 30c4570e928d..c18afd376d2a 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -42,6 +42,7 @@ struct fwnode_handle;
>  struct iommu_ops;
>  struct iommu_group;
>  struct iommu_fwspec;
> +struct pci_dev;
> 
>  struct bus_attribute {
>  	struct attribute	attr;
> @@ -860,6 +861,9 @@ struct dev_links_info {
>   * 		segment limitations.
>   * @dma_pools:	Dma pools (if dma'ble device).
>   * @dma_mem:	Internal for coherent mem override.
> + * @pci_dev:	PCI device associated with this device. Used by DMA
> mapping
> + *		operations on architectures that need access to PCI device
> + *		members that are not in struct device.
>   * @cma_area:	Contiguous memory area for dma allocations
>   * @archdata:	For arch-specific additions.
>   * @of_node:	Associated device tree node.
> @@ -940,6 +944,7 @@ struct device {
> 
>  	struct dma_coherent_mem	*dma_mem; /* internal for coherent
> mem
>  					     override */
> +	struct pci_dev		*pci_dev; /* for DMA mapping operations */

Compilation would break when CONFIG_PCI is not defined for some embedded platforms.
More than that, including specific pci_dev structure pointer in generic structure such as device just doesn't sound right.
I tested equivalent patch that you sent, but I don't think this is right direction to fix this bug.

>  #ifdef CONFIG_DMA_CMA
>  	struct cma *cma_area;		/* contiguous memory area for dma
>  					   allocations */
> diff --git a/include/linux/pci.h b/include/linux/pci.h index
> eb3da1a04e6c..eca790eaae20 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -409,7 +409,10 @@ static inline struct pci_dev *pci_physfn(struct
> pci_dev *dev)
> 
>  struct pci_dev *pci_alloc_dev(struct pci_bus *bus);
> 
> -#define	to_pci_dev(n) container_of(n, struct pci_dev, dev)
> +static inline struct pci_dev *to_pci_dev(const struct device *dev) {
> +	return dev->pci_dev;
> +}
>  #define for_each_pci_dev(d) while ((d = pci_get_device(PCI_ANY_ID,
> PCI_ANY_ID, d)) != NULL)
> 
>  static inline int pci_channel_offline(struct pci_dev *pdev)
> --
> 2.12.0
> 
> --
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