linux-kernel - Re: [PATCH 3/3] PCI: Add pci_read

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Message-ID: <20080804063833.GA21354@colo.lackof.org>
Date:	Mon, 4 Aug 2008 00:38:33 -0600
From:	Grant Grundler <grundler@...isc-linux.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	jbarnes@...tuousgeek.org, linux-kernel@...r.kernel.org,
	eric@...olt.net, Matthew Wilcox <willy@...ux.intel.com>
Subject: Re: [PATCH 3/3] PCI: Add pci_read_base() API

On Mon, Jul 28, 2008 at 01:39:01PM -0400, Matthew Wilcox wrote:
> Some devices have a BAR at a non-standard address.  The pci_read_base()
> API allows us to probe these BARs and fill in a resource for it as if
> they were standard BARs.

Willy,
Can you add a comment to the code listing the offending device?
That way we know how to test next time this code changes.

thanks,
grant

> 
> Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
> ---
>  drivers/pci/probe.c |   47 ++++++++++++++++++++++++++++++++++++++++-------
>  include/linux/pci.h |   10 ++++++++++
>  2 files changed, 50 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 2036300..a977d07 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -181,13 +181,6 @@ static u64 pci_size(u64 base, u64 maxbase, u64 mask)
>  	return size;
>  }
>  
> -enum pci_bar_type {
> -	pci_bar_unknown,	/* Standard PCI BAR probe */
> -	pci_bar_io,		/* An io port BAR */
> -	pci_bar_mem32,		/* A 32-bit memory BAR */
> -	pci_bar_mem64,		/* A 64-bit memory BAR */
> -};
> -
>  static inline enum pci_bar_type decode_bar(struct resource *res, u32 bar)
>  {
>  	if ((bar & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO) {
> @@ -300,6 +293,46 @@ static int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
>  	goto out;
>  }
>  
> +/**
> + * pci_read_base - Read a BAR from a specified location
> + * @dev: The PCI device to read
> + * @type: The type of BAR to read
> + * @res: A struct resource to be filled in
> + * @reg: The address in PCI config space to read the BAR from.
> + *
> + * Some devices have BARs in unusual places.  This function lets a driver ask
> + * the PCI subsystem to read it and place it in the resource tree.  If it is
> + * like a ROM BAR with an enable in bit 0, the caller should specify a @type
> + * of io, mem32 or mem64.  If it's like a normal BAR with memory type in the
> + * low bits, specify unknown, even if the caller knows what kind of BAR it is.
> + *
> + * Returns -ENXIO if the BAR was not successfully read.  If the BAR is read,
> + * but no suitable parent resource can be found for the BAR, this function
> + * returns -ENODEV.  If the resource cannot be inserted into the resource tree,
> + * it will return -EBUSY.  Note that the resource is still 'live' for these
> + * last two cases; the caller should set res->flags to 0 if this is not wanted.
> + */
> +int pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> +					struct resource *res, unsigned int reg)
> +{
> +	struct pci_bus_region region;
> +	struct resource *parent;
> +
> +	__pci_read_base(dev, type, res, reg);
> +	if (!res->flags)
> +		return -ENXIO;
> +
> +	region.start = res->start;
> +	region.end = res->end;
> +	pcibios_bus_to_resource(dev, res, &region);
> +
> +	parent = pci_find_parent_resource(dev, res);
> +	if (!parent)
> +		return -ENODEV;
> +	return request_resource(parent, res);
> +}
> +EXPORT_SYMBOL_GPL(pci_read_base);
> +
>  static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
>  {
>  	unsigned int pos, reg;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index a6a088e..f6ad5e8 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -310,6 +310,16 @@ struct pci_bus {
>  #define pci_bus_b(n)	list_entry(n, struct pci_bus, node)
>  #define to_pci_bus(n)	container_of(n, struct pci_bus, dev)
>  
> +enum pci_bar_type {
> +	pci_bar_unknown,	/* Standard PCI BAR probe */
> +	pci_bar_io,		/* An io port BAR */
> +	pci_bar_mem32,		/* A 32-bit memory BAR */
> +	pci_bar_mem64,		/* A 64-bit memory BAR */
> +};
> +
> +int pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> +					struct resource *res, unsigned int reg);
> +
>  /*
>   * Error values that may be returned by PCI functions.
>   */
> -- 
> 1.5.5.4
> --
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