Fix the problem of SATA devices within SAS enclosures

Adds a function designed to be callable any time (regardless of whether the transport attributes are configured or not) which returns true if the device is attached over a SAS transport. The design of this function is that transport specific functions can be embedded within a

if (is_sas_attached(sdev)) {
	...
}

which would be compiled out (and thus eliminate the symbols) if SAS is not configured.

Signed-off-by James Bottomley <[email protected]>

---
  drivers/scsi/scsi_transport_sas.c |   16 ++++++++++++++++
  include/scsi/scsi_transport_sas.h |    9 +++++++++
  2 files changed, 25 insertions(+), 0 deletions(-)

drivers/scsi/scsi_transport_sas.c +16 -0

index 30d26e3..b17f763 100644
@@ -341,6 +341,22 @@ static int do_sas_phy_delete(struct device *dev, void *data)
  }
 
  /**
+ * is_sas_attached - check if device is SAS attached
+ * @sdev: scsi device to check
+ *
+ * returns true if the device is SAS attached
+ */
+int is_sas_attached(struct scsi_device *sdev)
+{
+	struct Scsi_Host *shost = sdev->host;
+
+	return shost->transportt->host_attrs.ac.class ==
+		&sas_host_class.class;
+}
+EXPORT_SYMBOL(is_sas_attached);
+
+
+/**
   * sas_remove_children  -  tear down a devices SAS data structures
   * @dev:	device belonging to the sas object
   *

include/scsi/scsi_transport_sas.h +2 -0

index 0bd71e2..a8fdd10 100644
@@ -10,6 +10,15 @@ struct scsi_transport_template;
  struct sas_rphy;
  struct request;
 
+#if !IS_ENABLED(CONFIG_SCSI_SAS_ATTRS)
+static inline int is_sas_attached(struct scsi_device *sdev)

For a device known to be SAS connected, this will return the endpoint address. This is useful for getting the SAS address of SATA devices.

Signed-off-by James Bottomley <[email protected]>

---
  drivers/scsi/scsi_transport_sas.c |   14 ++++++++++++++
  include/scsi/scsi_transport_sas.h |    1 +
  2 files changed, 15 insertions(+), 0 deletions(-)

drivers/scsi/scsi_transport_sas.c +14 -0

index b17f763..80520e2 100644
@@ -383,6 +383,20 @@ void sas_remove_host(struct Scsi_Host *shost)
  EXPORT_SYMBOL(sas_remove_host);
 
  /**
+ * sas_get_address - return the SAS address of the device
+ * @sdev: scsi device
+ *
+ * Returns the SAS address of the scsi device
+ */
+u64 sas_get_address(struct scsi_device *sdev)
+{
+	struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
+
+	return rdev->rphy.identify.sas_address;
+}
+EXPORT_SYMBOL(sas_get_address);
+
+/**
   * sas_tlr_supported - checking TLR bit in vpd 0x90
   * @sdev: scsi device struct
   *

include/scsi/scsi_transport_sas.h +0 -0

index a8fdd10..13c0b2b 100644

Hi James,

[auto build test ERROR on v4.4-rc4]
[cannot apply to scsi/for-next next-20151209]

url:    https://github.com/0day-ci/linux/commits/James-Bottomley/Fix-the-problem-of-SATA-devices-within-SAS-enclosures/20151210-031802
config: i386-randconfig-b0-12100330 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

drivers/built-in.o: In function `ses_match_to_enclosure':

Quoted 2 lines

Quoted 2 lines

ses.c:(.text+0x1c04ad): undefined reference to is_sas_attached' ses.c:(.text+0x1c0519): undefined reference to sas_get_address'

The current discovery routines use the VPD 0x83 inquiry page to find the device SAS address and match it to the end point in the enclosure. This doesn't work for SATA devices because expanders (or hosts) simply make up an endpoint address for STP and thus the address returned by the VPD page never matches. Instead of doing this, for SAS attached devices, match by the direct endpoint address instead.

Signed-off-by James Bottomley <[email protected]>

drivers/scsi/Kconfig +1 -0

index 5f692ae..2a1d20e 100644
@@ -194,6 +194,7 @@ config CHR_DEV_SCH
  config SCSI_ENCLOSURE
  	tristate "SCSI Enclosure Support"
  	depends on SCSI && ENCLOSURE_SERVICES
+	depends on m || SCSI_SAS_ATTRS != m
  	help
  	  Enclosures are devices sitting on or in SCSI backplanes that
  	  manage devices.  If you have a disk cage, the chances are that

drivers/scsi/ses.c +2 -14

index 7d9cec5..1736935 100644
@@ -34,6 +34,8 @@
  #include <scsi/scsi_driver.h>
  #include <scsi/scsi_host.h>
 
+#include <scsi/scsi_transport_sas.h>
+
  struct ses_device {
  	unsigned char *page1;
  	unsigned char *page1_types;

@@ -571,31 +573,15 @@ static void ses_enclosure_data_process(struct enclosure_device *edev,
  static void ses_match_to_enclosure(struct enclosure_device *edev,
  				   struct scsi_device *sdev)
  {
-	unsigned char *desc;
  	struct efd efd = {
  		.addr = 0,
  	};
 
  	ses_enclosure_data_process(edev, to_scsi_device(edev->edev.parent), 0);
 
-	if (!sdev->vpd_pg83_len)
-		return;
-
-	desc = sdev->vpd_pg83 + 4;
-	while (desc < sdev->vpd_pg83 + sdev->vpd_pg83_len) {
-		enum scsi_protocol proto = desc[0] >> 4;
-		u8 code_set = desc[0] & 0x0f;
-		u8 piv = desc[1] & 0x80;
-		u8 assoc = (desc[1] & 0x30) >> 4;
-		u8 type = desc[1] & 0x0f;
-		u8 len = desc[3];
-
-		if (piv && code_set == 1 && assoc == 1