[PATCH 1/2] usb: storage: refactor usb 32-bit capacity read

[Ahmad Fatoum]

usb_stor_read_capacity uses SCSI Read Capacity 10, which assumes
capacity never exceeds 32-bit, which equals 2TiB max capacity at
512 byte sector size.

In preparation for porting support for SCSI Read Capacity 16 from
Linux, move over all Read Capacity 10 related code into a single
function. Some more refactoring is done to make the function look
more like the Linux implementation. This also makes it easier to spot
the differences in retry/timeout handling, which we might want to
adopt in future.

No functional change intended.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 drivers/usb/storage/usb.c | 62 +++++++++++++++++++++------------------
 1 file changed, 33 insertions(+), 29 deletions(-)

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index c264dd4b71e2..122af659820f 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -157,31 +157,49 @@ static int usb_stor_test_unit_ready(struct us_blk_dev *usb_blkdev)
 	return 0;
 }
 
-static int usb_stor_read_capacity(struct us_blk_dev *usb_blkdev,
-				  u32 *last_lba, u32 *block_length)
+static int read_capacity_10(struct us_blk_dev *usb_blkdev)
 {
 	struct device_d *dev = &usb_blkdev->us->pusb_dev->dev;
+	unsigned char cmd[16];
 	const u32 datalen = 8;
-	u32 *data = xzalloc(datalen);
-	u8 cmd[10];
+	__be32 *data = xzalloc(datalen);
 	int ret;
+	sector_t lba;
+	unsigned sector_size;
 
 	memset(cmd, 0, sizeof(cmd));
 	cmd[0] = SCSI_RD_CAPAC;
 
 	ret = usb_stor_transport(usb_blkdev, cmd, sizeof(cmd), data, datalen,
 				 3, USB_STOR_NO_REQUEST_SENSE);
-	if (ret < 0)
-		goto exit;
 
-	dev_dbg(dev, "Read Capacity returns: 0x%x, 0x%x\n",
-		data[0], data[1]);
-	*last_lba = be32_to_cpu(data[0]);
-	*block_length = be32_to_cpu(data[1]);
+	if (ret < 0) {
+		dev_dbg(dev, "Cannot read device capacity\n");
+		return ret;
+	}
 
-exit:
-	free(data);
-	return ret;
+	sector_size = be32_to_cpu(data[1]);
+	lba = be32_to_cpu(data[0]);
+
+	dev_dbg(dev, "LBA (10) = 0x%llx w/ sector size = %u\n",
+		lba, sector_size);
+
+
+	if (lba == U32_MAX) {
+		lba = U32_MAX - 1;
+		dev_warn(dev,
+			 "Limiting device size due to 32 bit constraints\n");
+		/* To support LBA >= U32_MAX, a READ CAPACITY (16) should be issued instead */
+	}
+
+
+	if (sector_size != SECTOR_SIZE)
+		dev_warn(dev, "Support only %d bytes sectors\n", SECTOR_SIZE);
+
+	usb_blkdev->blk.num_blocks = lba + 1;
+	usb_blkdev->blk.blockbits = SECTOR_SHIFT;
+
+	return SECTOR_SIZE;
 }
 
 static int usb_stor_io_10(struct us_blk_dev *usb_blkdev, u8 opcode,
@@ -275,7 +293,6 @@ static int usb_stor_init_blkdev(struct us_blk_dev *pblk_dev)
 {
 	struct us_data *us = pblk_dev->us;
 	struct device_d *dev = &us->pusb_dev->dev;
-	u32 last_lba = 0, block_length = 0;
 	int result;
 
 	/* get device info */
@@ -299,23 +316,10 @@ static int usb_stor_init_blkdev(struct us_blk_dev *pblk_dev)
 	/* read capacity */
 	dev_dbg(dev, "Reading capacity\n");
 
-	result = usb_stor_read_capacity(pblk_dev, &last_lba, &block_length);
-	if (result < 0) {
-		dev_dbg(dev, "Cannot read device capacity\n");
+	result = read_capacity_10(pblk_dev);
+	if (result < 0)
 		return result;
-	}
-
-	if (last_lba == U32_MAX) {
-		last_lba = U32_MAX - 1;
-		dev_warn(dev,
-			 "Limiting device size due to 32 bit constraints\n");
-		/* To support LBA >= U32_MAX, a READ CAPACITY (16) should be issued here */
-	}
 
-	pblk_dev->blk.num_blocks = last_lba + 1;
-	if (block_length != SECTOR_SIZE)
-		pr_warn("Support only %d bytes sectors\n", SECTOR_SIZE);
-	pblk_dev->blk.blockbits = SECTOR_SHIFT;
 	dev_dbg(dev, "Capacity = 0x%llx, blockshift = 0x%x\n",
 		 pblk_dev->blk.num_blocks, pblk_dev->blk.blockbits);
 
-- 
2.29.2