[PATCH] libata ata_data_xfer() fix

PATCH 1/2: ata_data_xfer() fix

Changes:
   - Modify ata_mmio_data_xfer() and ata_pio_data_xfer() to handle odd-lengthed buffer.
   - Add some function comments

This patch does not reuse ap->pad as alignment buffer since
using local variable seems good enough.

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 108 insertions, 3 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 73b1f72b7e43..8f6e536d8924 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -2519,6 +2519,20 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
 #endif /* __BIG_ENDIAN */
 }
 
+/**
+ *      ata_mmio_data_xfer - Transfer data by MMIO
+ *      @ap: port to read/write
+ *      @buf: data buffer
+ *      @buflen: buffer length
+ *      @do_write: read/write
+ *
+ *      Transfer data from/to the device data register by MMIO.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ */
+
 static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
                                unsigned int buflen, int write_data)
 {
@@ -2527,6 +2541,7 @@ static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
         u16 *buf16 = (u16 *) buf;
         void __iomem *mmio = (void __iomem *)ap->ioaddr.data_addr;
 
+        /* Transfer multiple of 2 bytes */
         if (write_data) {
                 for (i = 0; i < words; i++)
                         writew(le16_to_cpu(buf16[i]), mmio);
@@ -2534,19 +2549,76 @@ static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
                 for (i = 0; i < words; i++)
                         buf16[i] = cpu_to_le16(readw(mmio));
         }
+
+        /* Transfer trailing 1 byte, if any. */
+        if (unlikely(buflen & 0x01)) {
+                u16 align_buf[1] = { 0 };
+                unsigned char *trailing_buf = buf + buflen - 1;
+
+                if (write_data) {
+                        memcpy(align_buf, trailing_buf, 1);
+                        writew(le16_to_cpu(align_buf[0]), mmio);
+                } else {
+                        align_buf[0] = cpu_to_le16(readw(mmio));
+                        memcpy(trailing_buf, align_buf, 1);
+                }
+        }
 }
 
+/**
+ *      ata_pio_data_xfer - Transfer data by PIO
+ *      @ap: port to read/write
+ *      @buf: data buffer
+ *      @buflen: buffer length
+ *      @do_write: read/write
+ *
+ *      Transfer data from/to the device data register by PIO.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ */
+
 static void ata_pio_data_xfer(struct ata_port *ap, unsigned char *buf,
                               unsigned int buflen, int write_data)
 {
-        unsigned int dwords = buflen >> 1;
+        unsigned int words = buflen >> 1;
 
+        /* Transfer multiple of 2 bytes */
         if (write_data)
-                outsw(ap->ioaddr.data_addr, buf, dwords);
+                outsw(ap->ioaddr.data_addr, buf, words);
         else
-                insw(ap->ioaddr.data_addr, buf, dwords);
+                insw(ap->ioaddr.data_addr, buf, words);
+
+        /* Transfer trailing 1 byte, if any. */
+        if (unlikely(buflen & 0x01)) {
+                u16 align_buf[1] = { 0 };
+                unsigned char *trailing_buf = buf + buflen - 1;
+
+                if (write_data) {
+                        memcpy(align_buf, trailing_buf, 1);
+                        outw(le16_to_cpu(align_buf[0]), ap->ioaddr.data_addr);
+                } else {
+                        align_buf[0] = cpu_to_le16(inw(ap->ioaddr.data_addr));
+                        memcpy(trailing_buf, align_buf, 1);
+                }
+        }
 }
 
+/**
+ *      ata_data_xfer - Transfer data from/to the data register.
+ *      @ap: port to read/write
+ *      @buf: data buffer
+ *      @buflen: buffer length
+ *      @do_write: read/write
+ *
+ *      Transfer data from/to the device data register.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ */
+
 static void ata_data_xfer(struct ata_port *ap, unsigned char *buf,
                           unsigned int buflen, int do_write)
 {
@@ -2556,6 +2628,16 @@ static void ata_data_xfer(struct ata_port *ap, unsigned char *buf,
                 ata_pio_data_xfer(ap, buf, buflen, do_write);
 }
 
+/**
+ *      ata_pio_sector - Transfer ATA_SECT_SIZE (512 bytes) of data.
+ *      @qc: Command on going
+ *
+ *      Transfer ATA_SECT_SIZE of data from/to the ATA device.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ */
+
 static void ata_pio_sector(struct ata_queued_cmd *qc)
 {
         int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
@@ -2594,6 +2676,18 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
         kunmap(page);
 }
 
+/**
+ *      __atapi_pio_bytes - Transfer data from/to the ATAPI device.
+ *      @qc: Command on going
+ *      @bytes: number of bytes
+ *
+ *      Transfer Transfer data from/to the ATAPI device.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ */
+
 static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 {
         int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
@@ -2645,6 +2739,17 @@ next_sg:
         }
 }
 
+/**
+ *      atapi_pio_bytes - Transfer data from/to the ATAPI device.
+ *      @qc: Command on going
+ *
+ *      Transfer Transfer data from/to the ATAPI device.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ */
+
 static void atapi_pio_bytes(struct ata_queued_cmd *qc)
 {
         struct ata_port *ap = qc->ap;