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Message-ID: <562AD631.3040603@gmail.com> Date: Fri, 23 Oct 2015 17:52:01 -0700 From: Alexander Duyck <alexander.duyck@...il.com> To: Hannes Reinecke <hare@...e.de>, Bjorn Helgaas <bhelgaas@...gle.com> Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] pci: Update VPD size with correct length On 10/23/2015 02:09 AM, Hannes Reinecke wrote: > PCI-2.2 VPD entries have a maximum size of 32k, but might actually > be smaller than that. To figure out the actual size one has to read > the VPD area until the 'end marker' is reached. > Trying to read VPD data beyond that marker results in 'interesting' > effects, from simple read errors to crashing the card. > This path modifies the attribute size to the avialable VPD size. > > Signed-off-by: Hannes Reinecke <hare@...e.de> > --- > drivers/pci/access.c | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > index 6bc9b12..4f8208e 100644 > --- a/drivers/pci/access.c > +++ b/drivers/pci/access.c > @@ -409,6 +409,34 @@ static int pci_vpd_f0_dev_check(struct pci_dev *dev) > return ret; > } > > +/** > + * pci_vpd_size - determine actual size of Vital Product Data > + * @dev: pci device struct > + * @old_size: current assumed size, also maximum allowed size > + * > + */ > +size_t > +pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size) > +{ > + loff_t off = 0; > + unsigned char header[1+2]; /* 1 byte tag, 2 bytes length */ > + > + while (off < old_size && pci_read_vpd(dev, off, 1, header)) { > + if (header[0] == 0x78) /* End tag descriptor */ > + return off + 1; > + if (header[0] & 0x80) { > + /* Large Resource Data Type Tag */ > + if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2) > + return off + 1; > + off += 3 + ((header[2] << 8) | header[1]); > + } else { > + /* Short Resource Data Type Tag */ > + off += 1 + (header[0] & 0x07); > + } > + } > + return old_size; > +} > + My understanding is that the end tag can have some data associated with it such as a checksum. What you may want to look at doing is process long tag and short tag bits first. Then you could do a mask and compare after and if ((header[0] & ~0x7) == 0x78) then you return off + 1. Also I was wondering if you have looked at the cxgb4 network driver? They are using the vpd read/write calls to access their EEPROM and I assume they are doing so outside the actual VPD fields. - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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