Re: drivers/scsi/sata_vsc.c: inconsistent NULL checking

["Dan Williams" <dan.j.williams@gmail.com>]

On 3/9/06, Adrian Bunk <bunk@stusta.de> wrote:
> The Coverity checker found this inconsistent NULL checking recently
> introduced by the following commit:
>
>   2ae5b30ff08cee422c7f6388a759f7
>   Author: Dan Williams <dan.j.williams@intel.com>
>   [PATCH] Necessary evil to get sata_vsc to initialize with Intel iq3124h hba
>
>
> In function vsc_sata_interrupt():
>
>         err_status = ap ? vsc_sata_scr_read(ap, SCR_ERROR) : 0;
>         vsc_sata_scr_write(ap, SCR_ERROR, err_status);
>
>
> vsc_sata_scr_write() always dereferences ap
> (since SCR_ERROR < SCR_CONTROL).
>
> Checking for NULL in one line and unconditionally dereferencing the
> variable in the next line can't be right.
>

The attached patch cleans up the code, and adds GD31244 to the driver
description in drivers/scsi/Kconfig.

Dan

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 3c606cf..d01edc3 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -587,10 +587,10 @@ config SCSI_SATA_VIA
 	  If unsure, say N.
 
 config SCSI_SATA_VITESSE
-	tristate "VITESSE VSC-7174 SATA support"
+	tristate "VITESSE VSC-7174 / INTEL 31244 SATA support"
 	depends on SCSI_SATA && PCI
 	help
-	  This option enables support for Vitesse VSC7174 Serial ATA.
+	  This option enables support for Vitesse VSC7174 and Intel 31244 Serial ATA.
 
 	  If unsure, say N.
 
diff --git a/drivers/scsi/sata_vsc.c b/drivers/scsi/sata_vsc.c
index e484e8d..5b65fc7 100644
--- a/drivers/scsi/sata_vsc.c
+++ b/drivers/scsi/sata_vsc.c
@@ -82,17 +82,20 @@
 #define VSC_SATA_PORT_OFFSET		0x200
 
 /* Error interrupt status bit offsets */
-#define VSC_SATA_INT_ERROR_E_OFFSET	2
-#define VSC_SATA_INT_ERROR_P_OFFSET	4
-#define VSC_SATA_INT_ERROR_T_OFFSET	5
-#define VSC_SATA_INT_ERROR_M_OFFSET	1
+#define VSC_SATA_INT_ERROR_CRC		(1 << 6)
+#define VSC_SATA_INT_ERROR_T		(1 << 5)
+#define VSC_SATA_INT_ERROR_P		(1 << 4)
+#define VSC_SATA_INT_ERROR_R		(1 << 3)
+#define VSC_SATA_INT_ERROR_E		(1 << 2)
+#define VSC_SATA_INT_ERROR_M		(1 << 1)
+#define VSC_SATA_INT_PHY_CHANGE	(1 << 0)
+#define VSC_SATA_INT_ERROR (VSC_SATA_INT_ERROR_CRC  + VSC_SATA_INT_ERROR_T + \
+			     VSC_SATA_INT_ERROR_P    + VSC_SATA_INT_ERROR_R + \
+			     VSC_SATA_INT_ERROR_E    + VSC_SATA_INT_ERROR_M + \
+			     VSC_SATA_INT_PHY_CHANGE)
+
 #define is_vsc_sata_int_err(port_idx, int_status) \
-	 (int_status & ((1 << (VSC_SATA_INT_ERROR_E_OFFSET + (8 * port_idx))) | \
-		        (1 << (VSC_SATA_INT_ERROR_P_OFFSET + (8 * port_idx))) | \
-		        (1 << (VSC_SATA_INT_ERROR_T_OFFSET + (8 * port_idx))) | \
-		        (1 << (VSC_SATA_INT_ERROR_M_OFFSET + (8 * port_idx)))   \
-		       )\
- 	 )
+	 (int_status & (VSC_SATA_INT_ERROR << (8 * port_idx)))
 
 
 static u32 vsc_sata_scr_read (struct ata_port *ap, unsigned int sc_reg)
@@ -215,14 +218,6 @@ static irqreturn_t vsc_sata_interrupt (i
 
 			ap = host_set->ports[i];
 
-			if (is_vsc_sata_int_err(i, int_status)) {
-				u32 err_status;
-				printk(KERN_DEBUG "%s: ignoring interrupt(s)\n", __FUNCTION__);
-				err_status = ap ? vsc_sata_scr_read(ap, SCR_ERROR) : 0;
-				vsc_sata_scr_write(ap, SCR_ERROR, err_status);
-				handled++;
-			}
-
 			if (ap && !(ap->flags &
 				    (ATA_FLAG_PORT_DISABLED|ATA_FLAG_NOINTR))) {
 				struct ata_queued_cmd *qc;
@@ -230,12 +225,26 @@ static irqreturn_t vsc_sata_interrupt (i
 				qc = ata_qc_from_tag(ap, ap->active_tag);
 				if (qc && (!(qc->tf.ctl & ATA_NIEN))) {
 					handled += ata_host_intr(ap, qc);
-				} else {
-					printk(KERN_DEBUG "%s: ignoring interrupt(s)\n", __FUNCTION__);
+				} else if (is_vsc_sata_int_err(i, int_status)) {
+					/*
+					 * On some chips (i.e. Intel 31244), an error 
+					 * interrupt will sneak in at initialization
+					 * time (phy state changes).  Clearing the SCR
+					 * error register is not required, but it prevents
+					 * the phy state change interrupts from recurring 
+					 * later.
+					 */
+					u32 err_status;
+					err_status = vsc_sata_scr_read(ap, SCR_ERROR);
+					printk(KERN_DEBUG "%s: clearing interrupt, "
+					       "status %x; sata err status %x\n",
+					       __FUNCTION__,
+					       int_status, err_status);
+					vsc_sata_scr_write(ap, SCR_ERROR, err_status);
+					/* Clear interrupt status */
 					ata_chk_status(ap);
 					handled++;
 				}
-
 			}
 		}
 	}