linux-kernel - RE: [PATCH v7 04/15] PCI: Add pci_find_vsec

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Date:   Thu, 18 Feb 2021 21:32:47 +0000
From:   Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Lukas Wunner <lukas@...ner.de>
Subject: RE: [PATCH v7 04/15] PCI: Add pci_find_vsec_capability() to find a
 specific VSEC

On Thu, Feb 18, 2021 at 19:27:30, Bjorn Helgaas <helgaas@...nel.org> 
wrote:

> On Thu, Feb 18, 2021 at 08:03:58PM +0100, Gustavo Pimentel wrote:
> > Add pci_find_vsec_capability() to locate a Vendor-Specific Extended
> > Capability with the specified VSEC ID.
> > 
> > The Vendor-Specific Extended Capability (VSEC) allows one or more
> > proprietary capabilities defined by the vendor which aren't standard
> > or shared between vendors.
> > 
> > Signed-off-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
> 
> Beautiful, thanks!
> 
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> > ---
> >  drivers/pci/pci.c   | 30 ++++++++++++++++++++++++++++++
> >  include/linux/pci.h |  1 +
> >  2 files changed, 31 insertions(+)
> > 
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index b9fecc2..aef217c 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -693,6 +693,36 @@ u8 pci_find_ht_capability(struct pci_dev *dev, int ht_cap)
> >  EXPORT_SYMBOL_GPL(pci_find_ht_capability);
> >  
> >  /**
> > + * pci_find_vsec_capability - Find a vendor-specific extended capability
> > + * @dev: PCI device to query
> > + * @vendor: Vendor ID for which capability is defined
> > + * @cap: Vendor-specific capability ID
> > + *
> > + * If @dev has Vendor ID @vendor, search for a VSEC capability with
> > + * VSEC ID @cap. If found, return the capability offset in
> > + * config space; otherwise return 0.
> > + */
> > +u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap)
> > +{
> > +	u16 vsec = 0;
> > +	u32 header;
> > +
> > +	if (vendor != dev->vendor)
> > +		return 0;
> > +
> > +	while ((vsec = pci_find_next_ext_capability(dev, vsec,
> > +						     PCI_EXT_CAP_ID_VNDR))) {
> > +		if (pci_read_config_dword(dev, vsec + PCI_VNDR_HEADER,
> > +					  &header) == PCIBIOS_SUCCESSFUL &&
> > +		    PCI_VNDR_HEADER_ID(header) == cap)
> > +			return vsec;
> > +	}
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(pci_find_vsec_capability);
> > +
> > +/**
> >   * pci_find_parent_resource - return resource region of parent bus of given
> >   *			      region
> >   * @dev: PCI device structure contains resources to be searched
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index b32126d..814f814 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1077,6 +1077,7 @@ u8 pci_find_next_ht_capability(struct pci_dev *dev, u8 pos, int ht_cap);
> >  u16 pci_find_ext_capability(struct pci_dev *dev, int cap);
> >  u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 pos, int cap);
> >  struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
> > +u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap);
> 
> If you do any updates for other reasons, slide this up one more line
> so we have:
> 
>   u16 pci_find_ext_capability(struct pci_dev *dev, int cap);
>   u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 pos, int cap);
>   u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap);
> 
>   struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
> 
> I don't know why pci_find_next_bus() got stuck with the capability
> things.  It doesn't have anything to do with finding capabilities.  It
> goes more with pci_get_device(), etc.
> 
> But don't roll the series just for that.

Thanks, Bjorn.
I can those arrangements if some request comes along.
I can also move the pci_find_next_bus() next to the pci_get_device() if 
you like.

-Gustavo

> 
> >  u64 pci_get_dsn(struct pci_dev *dev);
> >  
> > -- 
> > 2.7.4
> >