PCI/VPD: Add pci_vpd_alloc()

Several users of the VPD API use a fixed-size buffer and read the VPD into
it for further usage. This requires special handling for the case that the
buffer isn't big enough to hold the full VPD data.  Also the buffer is
often allocated on the stack, which isn't too nice.

Add pci_vpd_alloc() to dynamically allocate buffer of the correct size and
read VPD into it.

Link: https://lore.kernel.org/r/955ff598-0021-8446-f856-0c2c077635d7@gmail.com
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/vpd.c

@@ -270,6 +270,32 @@ const struct attribute_group pci_dev_vpd_attr_group = {
 	.is_bin_visible = vpd_attr_is_visible,
 };
 
+void *pci_vpd_alloc(struct pci_dev *dev, unsigned int *size)
+{
+	unsigned int len = dev->vpd.len;
+	void *buf;
+	int cnt;
+
+	if (!dev->vpd.cap)
+		return ERR_PTR(-ENODEV);
+
+	buf = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	cnt = pci_read_vpd(dev, 0, len, buf);
+	if (cnt != len) {
+		kfree(buf);
+		return ERR_PTR(-EIO);
+	}
+
+	if (size)
+		*size = len;
+
+	return buf;
+}
+EXPORT_SYMBOL_GPL(pci_vpd_alloc);
+
 int pci_vpd_find_tag(const u8 *buf, unsigned int len, u8 rdt)
 {
 	int i = 0;

include/linux/pci.h

@@ -2330,6 +2330,15 @@ static inline u8 pci_vpd_info_field_size(const u8 *info_field)
 	return info_field[2];
 }
 
+/**
+ * pci_vpd_alloc - Allocate buffer and read VPD into it
+ * @dev: PCI device
+ * @size: pointer to field where VPD length is returned
+ *
+ * Returns pointer to allocated buffer or an ERR_PTR in case of failure
+ */
+void *pci_vpd_alloc(struct pci_dev *dev, unsigned int *size);
+
 /**
  * pci_vpd_find_tag - Locates the Resource Data Type tag provided
  * @buf: Pointer to buffered vpd data