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@xxxxxxx>
---
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
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