[PATCH] spi: use linked lists rather than an array

This makes the SPI core and its users access transfers in the SPI message
structure as linked list not as an array, as discussed on LKML.

From: David Brownell <dbrownell@users.sourceforge.net>

  Updates including doc, bugfixes to the list code, add
  spi_message_add_tail().  Plus, initialize things _before_ grabbing the
  locks in some cases (in case it grows more expensive).  This also merges
  some bitbang updates of mine that didn't yet make it into the mm tree.

Signed-off-by: Vitaly Wool <vwool@ru.mvista.com>
Signed-off-by: Dmitry Pervushin <dpervushin@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/input/touchscreen/ads7846.c

@@ -155,10 +155,13 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
 	struct ser_req		*req = kzalloc(sizeof *req, SLAB_KERNEL);
 	int			status;
 	int			sample;
+	int 			i;
 
 	if (!req)
 		return -ENOMEM;
 
+	INIT_LIST_HEAD(&req->msg.transfers);
+
 	/* activate reference, so it has time to settle; */
 	req->xfer[0].tx_buf = &ref_on;
 	req->xfer[0].len = 1;
@@ -192,8 +195,8 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
 	/* group all the transfers together, so we can't interfere with
 	 * reading touchscreen state; disable penirq while sampling
 	 */
-	req->msg.transfers = req->xfer;
-	req->msg.n_transfer = 6;
+	for (i = 0; i < 6; i++)
+		spi_message_add_tail(&req->xfer[i], &req->msg);
 
 	disable_irq(spi->irq);
 	status = spi_sync(spi, &req->msg);
@@ -398,6 +401,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 	struct ads7846			*ts;
 	struct ads7846_platform_data	*pdata = spi->dev.platform_data;
 	struct spi_transfer		*x;
+	int				i;
 
 	if (!spi->irq) {
 		dev_dbg(&spi->dev, "no IRQ?\n");
@@ -500,8 +504,8 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 
 	CS_CHANGE(x[-1]);
 
-	ts->msg.transfers = ts->xfer;
-	ts->msg.n_transfer = x - ts->xfer;
+	for (i = 0; i < x - ts->xfer; i++)
+		spi_message_add_tail(&ts->xfer[i], &ts->msg);
 	ts->msg.complete = ads7846_rx;
 	ts->msg.context = ts;
 

drivers/mtd/devices/m25p80.c

@@ -245,6 +245,21 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 	if (from + len > flash->mtd.size)
 		return -EINVAL;
 
+	spi_message_init(&m);
+	memset(t, 0, (sizeof t));
+
+	t[0].tx_buf = flash->command;
+	t[0].len = sizeof(flash->command);
+	spi_message_add_tail(&t[0], &m);
+
+	t[1].rx_buf = buf;
+	t[1].len = len;
+	spi_message_add_tail(&t[1], &m);
+
+	/* Byte count starts at zero. */
+	if (retlen)
+		*retlen = 0;
+
 	down(&flash->lock);
 
 	/* Wait till previous write/erase is done. */
@@ -254,8 +269,6 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 		return 1;
 	}
 
-	memset(t, 0, (sizeof t));
-
 	/* NOTE:  OPCODE_FAST_READ (if available) is faster... */
 
 	/* Set up the write data buffer. */
@@ -264,19 +277,6 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 	flash->command[2] = from >> 8;
 	flash->command[3] = from;
 
-	/* Byte count starts at zero. */
-	if (retlen)
-		*retlen = 0;
-
-	t[0].tx_buf = flash->command;
-	t[0].len = sizeof(flash->command);
-
-	t[1].rx_buf = buf;
-	t[1].len = len;
-
-	m.transfers = t;
-	m.n_transfer = 2;
-
 	spi_sync(flash->spi, &m);
 
 	*retlen = m.actual_length - sizeof(flash->command);
@@ -313,6 +313,16 @@ static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len,
 	if (to + len > flash->mtd.size)
 		return -EINVAL;
 
+	spi_message_init(&m);
+	memset(t, 0, (sizeof t));
+
+	t[0].tx_buf = flash->command;
+	t[0].len = sizeof(flash->command);
+	spi_message_add_tail(&t[0], &m);
+
+	t[1].tx_buf = buf;
+	spi_message_add_tail(&t[1], &m);
+
   	down(&flash->lock);
 
 	/* Wait until finished previous write command. */
@@ -321,26 +331,17 @@ static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	write_enable(flash);
 
-	memset(t, 0, (sizeof t));
-
 	/* Set up the opcode in the write buffer. */
 	flash->command[0] = OPCODE_PP;
 	flash->command[1] = to >> 16;
 	flash->command[2] = to >> 8;
 	flash->command[3] = to;
 
-	t[0].tx_buf = flash->command;
-	t[0].len = sizeof(flash->command);
-
-	m.transfers = t;
-	m.n_transfer = 2;
-
 	/* what page do we start with? */
 	page_offset = to % FLASH_PAGESIZE;
 
 	/* do all the bytes fit onto one page? */
 	if (page_offset + len <= FLASH_PAGESIZE) {
-		t[1].tx_buf = buf;
 		t[1].len = len;
 
 		spi_sync(flash->spi, &m);
@@ -352,7 +353,6 @@ static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len,
 		/* the size of data remaining on the first page */
 		page_size = FLASH_PAGESIZE - page_offset;
 
-		t[1].tx_buf = buf;
 		t[1].len = page_size;
 		spi_sync(flash->spi, &m);
 

drivers/mtd/devices/mtd_dataflash.c

@@ -147,7 +147,7 @@ static int dataflash_erase(struct mtd_info *mtd, struct erase_info *instr)
 {
 	struct dataflash	*priv = (struct dataflash *)mtd->priv;
 	struct spi_device	*spi = priv->spi;
-	struct spi_transfer	x[1] = { { .tx_dma = 0, }, };
+	struct spi_transfer	x = { .tx_dma = 0, };
 	struct spi_message	msg;
 	unsigned		blocksize = priv->page_size << 3;
 	u8			*command;
@@ -162,10 +162,11 @@ static int dataflash_erase(struct mtd_info *mtd, struct erase_info *instr)
 			|| (instr->addr % priv->page_size) != 0)
 		return -EINVAL;
 
-	x[0].tx_buf = command = priv->command;
-	x[0].len = 4;
-	msg.transfers = x;
-	msg.n_transfer = 1;
+	spi_message_init(&msg);
+
+	x.tx_buf = command = priv->command;
+	x.len = 4;
+	spi_message_add_tail(&x, &msg);
 
 	down(&priv->lock);
 	while (instr->len > 0) {
@@ -256,12 +257,15 @@ static int dataflash_read(struct mtd_info *mtd, loff_t from, size_t len,
 	DEBUG(MTD_DEBUG_LEVEL3, "READ: (%x) %x %x %x\n",
 		command[0], command[1], command[2], command[3]);
 
+	spi_message_init(&msg);
+
 	x[0].tx_buf = command;
 	x[0].len = 8;
+	spi_message_add_tail(&x[0], &msg);
+
 	x[1].rx_buf = buf;
 	x[1].len = len;
-	msg.transfers = x;
-	msg.n_transfer = 2;
+	spi_message_add_tail(&x[1], &msg);
 
 	down(&priv->lock);
 
@@ -320,9 +324,11 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 	if ((to + len) > mtd->size)
 		return -EINVAL;
 
+	spi_message_init(&msg);
+
 	x[0].tx_buf = command = priv->command;
 	x[0].len = 4;
-	msg.transfers = x;
+	spi_message_add_tail(&x[0], &msg);
 
 	pageaddr = ((unsigned)to / priv->page_size);
 	offset = ((unsigned)to % priv->page_size);
@@ -364,7 +370,6 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 			DEBUG(MTD_DEBUG_LEVEL3, "TRANSFER: (%x) %x %x %x\n",
 				command[0], command[1], command[2], command[3]);
 
-			msg.n_transfer = 1;
 			status = spi_sync(spi, &msg);
 			if (status < 0)
 				DEBUG(MTD_DEBUG_LEVEL1, "%s: xfer %u -> %d \n",
@@ -385,14 +390,16 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 		x[1].tx_buf = writebuf;
 		x[1].len = writelen;
-		msg.n_transfer = 2;
+		spi_message_add_tail(x + 1, &msg);
 		status = spi_sync(spi, &msg);
+		spi_transfer_del(x + 1);
 		if (status < 0)
 			DEBUG(MTD_DEBUG_LEVEL1, "%s: pgm %u/%u -> %d \n",
 				spi->dev.bus_id, addr, writelen, status);
 
 		(void) dataflash_waitready(priv->spi);
 
+
 #ifdef	CONFIG_DATAFLASH_WRITE_VERIFY
 
 		/* (3) Compare to Buffer1 */
@@ -405,7 +412,6 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 		DEBUG(MTD_DEBUG_LEVEL3, "COMPARE: (%x) %x %x %x\n",
 			command[0], command[1], command[2], command[3]);
 
-		msg.n_transfer = 1;
 		status = spi_sync(spi, &msg);
 		if (status < 0)
 			DEBUG(MTD_DEBUG_LEVEL1, "%s: compare %u -> %d \n",

drivers/spi/spi.c

@@ -557,6 +557,17 @@ int spi_write_then_read(struct spi_device *spi,
 	if ((n_tx + n_rx) > SPI_BUFSIZ)
 		return -EINVAL;
 
+	spi_message_init(&message);
+	memset(x, 0, sizeof x);
+	if (n_tx) {
+		x[0].len = n_tx;
+		spi_message_add_tail(&x[0], &message);
+	}
+	if (n_rx) {
+		x[1].len = n_rx;
+		spi_message_add_tail(&x[1], &message);
+	}
+
 	/* ... unless someone else is using the pre-allocated buffer */
 	if (down_trylock(&lock)) {
 		local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
@@ -565,18 +576,11 @@ int spi_write_then_read(struct spi_device *spi,
 	} else
 		local_buf = buf;
 
-	memset(x, 0, sizeof x);
-
 	memcpy(local_buf, txbuf, n_tx);
 	x[0].tx_buf = local_buf;
-	x[0].len = n_tx;
-
 	x[1].rx_buf = local_buf + n_tx;
-	x[1].len = n_rx;
 
 	/* do the i/o */
-	message.transfers = x;
-	message.n_transfer = ARRAY_SIZE(x);
 	status = spi_sync(spi, &message);
 	if (status == 0) {
 		memcpy(rxbuf, x[1].rx_buf, n_rx);