[PATCH/RFC 4/4] CHS: optimize LBA28/LBA48 usage

[Albert Lee <albertcc@tw.ibm.com>]

Patch 4/4: optimize LBA28/LBA48 per Mark's advice.

Changes:
    - add lba_28_ok() and lba_48_ok() to ata.h
    - use lba_28_ok() for CHS range check
    - LBA28/LBA48 optimization

For your review, thanks.

Albert
Signed-off-by: Albert Lee <albertcc@tw.ibm.com>

=====

--- ch2/include/linux/ata.h    2005-10-05 18:11:12.000000000 +0800
+++ ch4/include/linux/ata.h    2005-10-05 18:12:09.000000000 +0800
@@ -291,4 +291,14 @@ static inline int ata_ok(u8 status)
             == ATA_DRDY);
 }
 
+static inline int lba_28_ok(u64 block, u32 n_block)
+{
+    return (block < ((u64)1 << 28)) && (n_block <= 256);
+}
+
+static inline int lba_48_ok(u64 block, u32 n_block)
+{
+    return (block < ((u64)1 << 48)) && (n_block <= 65536);
+}
+
 #endif /* __LINUX_ATA_H__ */
--- ch3/drivers/scsi/libata-scsi.c    2005-10-05 18:11:12.000000000 +0800
+++ ch4/drivers/scsi/libata-scsi.c    2005-10-05 18:12:09.000000000 +0800
@@ -633,8 +633,12 @@ static unsigned int ata_scsi_verify_xlat
     if (dev->flags & ATA_DFLAG_LBA) {
         tf->flags |= ATA_TFLAG_LBA;
 
-        if (dev->flags & ATA_DFLAG_LBA48) {
-            if (n_block > (64 * 1024))
+        if (lba_28_ok(block, n_block)) {
+            /* use LBA28 */
+            tf->command = ATA_CMD_VERIFY;
+            tf->device |= (block >> 24) & 0xf;
+        } else if (lba_48_ok(block, n_block)) {
+            if (!(dev->flags & ATA_DFLAG_LBA48))
                 return 1;
 
             /* use LBA48 */
@@ -646,14 +650,9 @@ static unsigned int ata_scsi_verify_xlat
             tf->hob_lbah = (block >> 40) & 0xff;
             tf->hob_lbam = (block >> 32) & 0xff;
             tf->hob_lbal = (block >> 24) & 0xff;
-        } else {
-            if (n_block > 256)
-                return 1;
-
-            /* use LBA28 */
-            tf->command = ATA_CMD_VERIFY;
-            tf->device |= (block >> 24) & 0xf;
-        }
+        } else
+            /* request too large even for LBA48 */
+            return 1;
 
         tf->nsect = n_block & 0xff;
 
@@ -666,7 +665,7 @@ static unsigned int ata_scsi_verify_xlat
         /* CHS */
         u32 sect, head, cyl, track;
 
-        if (n_block > 256)
+        if (!lba_28_ok(block, n_block))
             return 1;
 
         /* Convert LBA to CHS */
@@ -766,9 +765,11 @@ static unsigned int ata_scsi_rw_xlat(str
     if (dev->flags & ATA_DFLAG_LBA) {
         tf->flags |= ATA_TFLAG_LBA;
 
-        if (dev->flags & ATA_DFLAG_LBA48) {
-            /* The request -may- be too large for LBA48. */
-            if ((block >> 48) || (n_block > 65536))
+        if (lba_28_ok(block, n_block)) {
+            /* use LBA28 */
+            tf->device |= (block >> 24) & 0xf;
+        } else if (lba_48_ok(block, n_block)) {
+            if (!(dev->flags & ATA_DFLAG_LBA48))
                 return 1;
 
             /* use LBA48 */
@@ -779,15 +780,9 @@ static unsigned int ata_scsi_rw_xlat(str
             tf->hob_lbah = (block >> 40) & 0xff;
             tf->hob_lbam = (block >> 32) & 0xff;
             tf->hob_lbal = (block >> 24) & 0xff;
-        } else {
-            /* use LBA28 */
-
-            /* The request -may- be too large for LBA28. */
-            if ((block >> 28) || (n_block > 256))
-                return 1;
-
-            tf->device |= (block >> 24) & 0xf;
-        }
+        } else
+            /* request too large even for LBA48 */
+            return 1;
 
         ata_rwcmd_protocol(qc);
 
@@ -804,7 +799,7 @@ static unsigned int ata_scsi_rw_xlat(str
         u32 sect, head, cyl, track;
 
         /* The request -may- be too large for CHS addressing. */
-        if ((block >> 28) || (n_block > 256))
+        if (!lba_28_ok(block, n_block))
             return 1;
 
         ata_rwcmd_protocol(qc);