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RE: [PATCH 1/2] device: Stop requiring that struct device is embedded in struct pci_dev

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  RE: [PATCH 1/2] device: Stop requiring that struct device is embedded  in struct pci_dev Parav Pandit <parav@mellanox.com> - 2017-03-07 03:50 +0100
    Re: [PATCH 1/2] device: Stop requiring that struct device is  embedded in struct pci_dev "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org> - 2017-03-07 10:10 +0100

#1593868 — RE: [PATCH 1/2] device: Stop requiring that struct device is embedded in struct pci_dev

Hi Bart,

> -----Original Message-----
> From: linux-rdma-owner@vger.kernel.org [mailto:linux-rdma-
> owner@vger.kernel.org] On Behalf Of Bart Van Assche
> Sent: Monday, March 6, 2017 6:36 PM
> To: Doug Ledford <dledford@redhat.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Sebastian Ott
> <sebott@linux.vnet.ibm.com>; Parav Pandit <parav@mellanox.com>; linux-
> rdma@vger.kernel.org; linux-kernel@vger.kernel.org; Bart Van Assche
> <bart.vanassche@sandisk.com>; Bjorn Helgaas <bhelgaas@google.com>;
> Benjamin Herrenschmidt <benh@kernel.crashing.org>; David Woodhouse
> <dwmw2@infradead.org>; H . Peter Anvin <hpa@zytor.com>; Ingo Molnar
> <mingo@redhat.com>; Russell King <linux@armlinux.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@sandisk.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Russell King <linux@armlinux.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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#1594018 — Re: [PATCH 1/2] device: Stop requiring that struct device is embedded in struct pci_dev

On Tue, Mar 07, 2017 at 02:44:28AM +0000, Bart Van Assche wrote:
> On Tue, 2017-03-07 at 02:41 +0000, Parav Pandit wrote:
> > 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.
> 
> You are welcome to voice your opinion. But unless anyone proposes a better
> alternative I propose to proceed with this approach.

That's not how development happens.  You don't just do "here's a
something I came up with, if you don't like it, tough!"  If people
object, you need to resolve those objections, not ignore them.

Especially when you are breaking the build!!!

come on now, you know better than this.

greg k-h

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