[SCSI] Add VPD helper
Based on prior work by Martin Petersen and James Bottomley, this patch
adds a generic helper for retrieving VPD pages from SCSI devices.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index cbcd3f6..a2ef032 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -967,6 +967,110 @@
EXPORT_SYMBOL(scsi_track_queue_full);
/**
+ * scsi_vpd_inquiry - Request a device provide us with a VPD page
+ * @sdev: The device to ask
+ * @buffer: Where to put the result
+ * @page: Which Vital Product Data to return
+ * @len: The length of the buffer
+ *
+ * This is an internal helper function. You probably want to use
+ * scsi_get_vpd_page instead.
+ *
+ * Returns 0 on success or a negative error number.
+ */
+static int scsi_vpd_inquiry(struct scsi_device *sdev, unsigned char *buffer,
+ u8 page, unsigned len)
+{
+ int result;
+ unsigned char cmd[16];
+
+ cmd[0] = INQUIRY;
+ cmd[1] = 1; /* EVPD */
+ cmd[2] = page;
+ cmd[3] = len >> 8;
+ cmd[4] = len & 0xff;
+ cmd[5] = 0; /* Control byte */
+
+ /*
+ * I'm not convinced we need to try quite this hard to get VPD, but
+ * all the existing users tried this hard.
+ */
+ result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
+ len + 4, NULL, 30 * HZ, 3, NULL);
+ if (result)
+ return result;
+
+ /* Sanity check that we got the page back that we asked for */
+ if (buffer[1] != page)
+ return -EIO;
+
+ return 0;
+}
+
+/**
+ * scsi_get_vpd_page - Get Vital Product Data from a SCSI device
+ * @sdev: The device to ask
+ * @page: Which Vital Product Data to return
+ *
+ * SCSI devices may optionally supply Vital Product Data. Each 'page'
+ * of VPD is defined in the appropriate SCSI document (eg SPC, SBC).
+ * If the device supports this VPD page, this routine returns a pointer
+ * to a buffer containing the data from that page. The caller is
+ * responsible for calling kfree() on this pointer when it is no longer
+ * needed. If we cannot retrieve the VPD page this routine returns %NULL.
+ */
+unsigned char *scsi_get_vpd_page(struct scsi_device *sdev, u8 page)
+{
+ int i, result;
+ unsigned int len;
+ unsigned char *buf = kmalloc(259, GFP_KERNEL);
+
+ if (!buf)
+ return NULL;
+
+ /* Ask for all the pages supported by this device */
+ result = scsi_vpd_inquiry(sdev, buf, 0, 255);
+ if (result)
+ goto fail;
+
+ /* If the user actually wanted this page, we can skip the rest */
+ if (page == 0)
+ return buf;
+
+ for (i = 0; i < buf[3]; i++)
+ if (buf[i + 4] == page)
+ goto found;
+ /* The device claims it doesn't support the requested page */
+ goto fail;
+
+ found:
+ result = scsi_vpd_inquiry(sdev, buf, page, 255);
+ if (result)
+ goto fail;
+
+ /*
+ * Some pages are longer than 255 bytes. The actual length of
+ * the page is returned in the header.
+ */
+ len = (buf[2] << 8) | buf[3];
+ if (len <= 255)
+ return buf;
+
+ kfree(buf);
+ buf = kmalloc(len + 4, GFP_KERNEL);
+ result = scsi_vpd_inquiry(sdev, buf, page, len);
+ if (result)
+ goto fail;
+
+ return buf;
+
+ fail:
+ kfree(buf);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(scsi_get_vpd_page);
+
+/**
* scsi_device_get - get an additional reference to a scsi_device
* @sdev: device to get a reference to
*