Patchwork mtd: sh: maple: Support the Dreamcast visual memory unit as a flash mapping

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Submitter Adrian McMenamin
Date March 4, 2009, 12:31 a.m.
Message ID <1236126664.6544.10.camel@localhost.localdomain>
Download mbox | patch
Permalink /patch/24142/
State New, archived
Headers show

Comments

Adrian McMenamin - March 4, 2009, 12:31 a.m.
(David, I am posting this again as I haven't seen any comment from you on it -
apologies if I have missed any. Paul has accepted the maple bus patches needed
to make it work and these are now in linux-next. I have removed copy recipients
not directly interested in this now it is separated out from the maple bus patch.)

This patch adds support for the Sega Dreamcast visual memory unit as a
flash mapping. It requires changes in the maple bus driver (posted
separately) to support block reads and writes.

The VMU is a 'smart' flash device, with a built-in 8-bit controller -
for instance there is an erase before a write but it is hidden from the
user. But the device's overall behaviour means it works well with the
mtd layer and it is appropriate to add it as an mtd mapping.

Signed-off-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
---

Patch

diff --git a/drivers/mtd/maps/Kconfig b/drivers/mtd/maps/Kconfig
index 0225cbb..9b3e564 100644
--- a/drivers/mtd/maps/Kconfig
+++ b/drivers/mtd/maps/Kconfig
@@ -551,5 +551,15 @@  config MTD_PLATRAM
 
 	  This selection automatically selects the map_ram driver.
 
-endmenu
+config MTD_VMU
+	tristate "Map driver for Dreamcast VMU"
+	depends on MAPLE
+	help
+	  This driver enables access to the Dreamcast Visual Memory Unit (VMU).
+
+	  Most Dreamcast users will want to say Y here.
 
+	  To build this as a module select M here, the module will be called
+	  vmu-flash.
+
+endmenu
diff --git a/drivers/mtd/maps/Makefile b/drivers/mtd/maps/Makefile
index 6d9ba35..26b28a7 100644
--- a/drivers/mtd/maps/Makefile
+++ b/drivers/mtd/maps/Makefile
@@ -61,3 +61,4 @@  obj-$(CONFIG_MTD_PLATRAM)	+= plat-ram.o
 obj-$(CONFIG_MTD_OMAP_NOR)	+= omap_nor.o
 obj-$(CONFIG_MTD_INTEL_VR_NOR)	+= intel_vr_nor.o
 obj-$(CONFIG_MTD_BFIN_ASYNC)	+= bfin-async-flash.o
+obj-$(CONFIG_MTD_VMU)		+= vmu-flash.o
diff --git a/drivers/mtd/maps/vmu-flash.c b/drivers/mtd/maps/vmu-flash.c
new file mode 100644
index 0000000..1f73297
--- /dev/null
+++ b/drivers/mtd/maps/vmu-flash.c
@@ -0,0 +1,832 @@ 
+/* vmu-flash.c
+ * Driver for SEGA Dreamcast Visual Memory Unit
+ *
+ * Copyright (c) Adrian McMenamin 2002 - 2009
+ * Copyright (c) Paul Mundt 2001
+ *
+ * Licensed under version 2 of the
+ * GNU General Public Licence
+ */
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/maple.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/map.h>
+
+struct vmu_cache {
+	unsigned char *buffer;		/* Cache */
+	unsigned int block;		/* Which block was cached */
+	unsigned long jiffies_atc;	/* When was it cached? */
+	int valid;
+};
+
+struct mdev_part {
+	struct maple_device *mdev;
+	int partition;
+};
+
+struct vmupart {
+	u16 user_blocks;
+	u16 root_block;
+	u16 numblocks;
+	char *name;
+	struct vmu_cache *pcache;
+};
+
+struct memcard {
+	u16 tempA;
+	u16 tempB;
+	u32 partitions;
+	u32 blocklen;
+	u32 writecnt;
+	u32 readcnt;
+	u32 removeable;
+	int partition;
+	int read;
+	unsigned char *blockread;
+	struct vmupart *parts;
+	struct mtd_info *mtd;
+};
+
+struct vmu_block {
+	unsigned int num; /* block number */
+	unsigned int ofs; /* block offset */
+};
+
+static struct vmu_block *ofs_to_block(unsigned long src_ofs,
+	struct mtd_info *mtd, int partition)
+{
+	struct vmu_block *vblock;
+	struct maple_device *mdev;
+	struct memcard *card;
+	struct mdev_part *mpart;
+	int num;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	card = maple_get_drvdata(mdev);
+
+	if (src_ofs >= card->parts[partition].numblocks * card->blocklen)
+		goto failed;
+
+	num = src_ofs / card->blocklen;
+	if (num > card->parts[partition].numblocks)
+		goto failed;
+
+	vblock = kmalloc(sizeof(struct vmu_block), GFP_KERNEL);
+	if (!vblock)
+		goto failed;
+
+	vblock->num = num;
+	vblock->ofs = src_ofs % card->blocklen;
+	return vblock;
+
+failed:
+	return NULL;
+}
+
+/* Maple bus callback function for reads */
+static void vmu_blockread(struct mapleq *mq)
+{
+	struct maple_device *mdev;
+	struct memcard *card;
+
+	mdev = mq->dev;
+	card = maple_get_drvdata(mdev);
+	/* copy the read in data */
+
+	if (unlikely(!card->blockread))
+		return;
+
+	memcpy(card->blockread, mq->recvbuf->buf + 12,
+		card->blocklen/card->readcnt);
+
+}
+
+/* Interface with maple bus to read blocks
+ * caching the results so that other parts
+ * of the driver can access block reads */
+static int maple_vmu_read_block(unsigned int num, unsigned char *buf,
+	struct mtd_info *mtd)
+{
+	struct memcard *card;
+	struct mdev_part *mpart;
+	struct maple_device *mdev;
+	int partition, error = 0, x, wait;
+	unsigned char *blockread = NULL;
+	struct vmu_cache *pcache;
+	__be32 sendbuf;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	partition = mpart->partition;
+	card = maple_get_drvdata(mdev);
+	pcache = card->parts[partition].pcache;
+	pcache->valid = 0;
+
+	/* prepare the cache for this block */
+	if (!pcache->buffer) {
+		pcache->buffer = kmalloc(card->blocklen, GFP_KERNEL);
+		if (!pcache->buffer) {
+			dev_err(&mdev->dev, "VMU at (%d, %d) - read fails due"
+				" to lack of memory\n", mdev->port,
+				mdev->unit);
+			error = -ENOMEM;
+			goto outB;
+		}
+	}
+
+	/*
+	* Reads may be phased - again the hardware spec
+	* supports this - though may not be any devices in
+	* the wild that implement it, but we will here
+	*/
+	for (x = 0; x < card->readcnt; x++) {
+		sendbuf = cpu_to_be32(partition << 24 | x << 16 | num);
+
+		if (atomic_read(&mdev->busy) == 1) {
+			wait_event_interruptible_timeout(mdev->maple_wait,
+				atomic_read(&mdev->busy) == 0, HZ);
+			if (atomic_read(&mdev->busy) == 1) {
+				dev_notice(&mdev->dev, "VMU at (%d, %d)"
+					" is busy\n", mdev->port, mdev->unit);
+				error = -EAGAIN;
+				goto outB;
+			}
+		}
+
+		atomic_set(&mdev->busy, 1);
+		blockread = kmalloc(card->blocklen/card->readcnt, GFP_KERNEL);
+		if (!blockread) {
+			error = -ENOMEM;
+			atomic_set(&mdev->busy, 0);
+			goto outB;
+		}
+		card->blockread = blockread;
+
+		maple_getcond_callback(mdev, vmu_blockread, 0,
+			MAPLE_FUNC_MEMCARD);
+		error = maple_add_packet(mdev, MAPLE_FUNC_MEMCARD,
+				MAPLE_COMMAND_BREAD, 2, &sendbuf);
+		/* Very long timeouts seem to be needed when box is stressed */
+		wait = wait_event_interruptible_timeout(mdev->maple_wait,
+			(atomic_read(&mdev->busy) == 0 ||
+			atomic_read(&mdev->busy) == 2), HZ * 3);
+		/*
+		* MTD layer does not handle hotplugging well
+		* so have to return errors when VMU is unplugged
+		* in the middle of a read (busy == 2)
+		*/
+		if (error || atomic_read(&mdev->busy) == 2) {
+			if (atomic_read(&mdev->busy) == 2)
+				error = -ENXIO;
+			atomic_set(&mdev->busy, 0);
+			card->blockread = NULL;
+			goto outA;
+		}
+		if (wait == 0 || wait == -ERESTARTSYS) {
+			card->blockread = NULL;
+			atomic_set(&mdev->busy, 0);
+			error = -EIO;
+			list_del_init(&(mdev->mq->list));
+			kfree(mdev->mq->sendbuf);
+			mdev->mq->sendbuf = NULL;
+			if (wait == -ERESTARTSYS) {
+				dev_warn(&mdev->dev, "VMU read on (%d, %d)"
+					" interrupted on block 0x%X\n",
+					mdev->port, mdev->unit, num);
+			} else
+				dev_notice(&mdev->dev, "VMU read on (%d, %d)"
+					" timed out on block 0x%X\n",
+					mdev->port, mdev->unit, num);
+			goto outA;
+		}
+
+		memcpy(buf + (card->blocklen/card->readcnt) * x, blockread,
+			card->blocklen/card->readcnt);
+
+		memcpy(pcache->buffer + (card->blocklen/card->readcnt) * x,
+			card->blockread, card->blocklen/card->readcnt);
+		card->blockread = NULL;
+		pcache->block = num;
+		pcache->jiffies_atc = jiffies;
+		pcache->valid = 1;
+		kfree(blockread);
+	}
+
+	return error;
+
+outA:
+	kfree(blockread);
+outB:
+	return error;
+}
+
+/* communicate with maple bus for phased writing */
+static int maple_vmu_write_block(unsigned int num, const unsigned char *buf,
+	struct mtd_info *mtd)
+{
+	struct memcard *card;
+	struct mdev_part *mpart;
+	struct maple_device *mdev;
+	int partition, error, locking, x, phaselen, wait;
+	__be32 *sendbuf;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	partition = mpart->partition;
+	card = maple_get_drvdata(mdev);
+
+	phaselen = card->blocklen/card->writecnt;
+
+	sendbuf = kmalloc(phaselen + 4, GFP_KERNEL);
+	if (!sendbuf) {
+		error = -ENOMEM;
+		goto fail_nosendbuf;
+	}
+	for (x = 0; x < card->writecnt; x++) {
+		sendbuf[0] = cpu_to_be32(partition << 24 | x << 16 | num);
+		memcpy(&sendbuf[1], buf + phaselen * x, phaselen);
+		/* wait until the device is not busy doing something else
+		* or 1 second - which ever is longer */
+		if (atomic_read(&mdev->busy) == 1) {
+			wait_event_interruptible_timeout(mdev->maple_wait,
+				atomic_read(&mdev->busy) == 0, HZ);
+			if (atomic_read(&mdev->busy) == 1) {
+				error = -EBUSY;
+				dev_notice(&mdev->dev, "VMU write at (%d, %d)"
+					"failed - device is busy\n",
+					mdev->port, mdev->unit);
+				goto fail_nolock;
+			}
+		}
+		atomic_set(&mdev->busy, 1);
+
+		locking = maple_add_packet(mdev, MAPLE_FUNC_MEMCARD,
+			MAPLE_COMMAND_BWRITE, phaselen / 4 + 2, sendbuf);
+		wait = wait_event_interruptible_timeout(mdev->maple_wait,
+			atomic_read(&mdev->busy) == 0, HZ/10);
+		if (locking) {
+			error = -EIO;
+			atomic_set(&mdev->busy, 0);
+			goto fail_nolock;
+		}
+		if (atomic_read(&mdev->busy) == 2) {
+			atomic_set(&mdev->busy, 0);
+		} else if (wait == 0 || wait == -ERESTARTSYS) {
+			error = -EIO;
+			dev_warn(&mdev->dev, "Write at (%d, %d) of block"
+				" 0x%X at phase %d failed: could not"
+				" communicate with VMU", mdev->port,
+				mdev->unit, num, x);
+			atomic_set(&mdev->busy, 0);
+			kfree(mdev->mq->sendbuf);
+			mdev->mq->sendbuf = NULL;
+			list_del_init(&(mdev->mq->list));
+			goto fail_nolock;
+		}
+	}
+	kfree(sendbuf);
+
+	return card->blocklen;
+
+fail_nolock:
+	kfree(sendbuf);
+fail_nosendbuf:
+	dev_err(&mdev->dev, "VMU (%d, %d): write failed\n", mdev->port,
+		mdev->unit);
+	return error;
+}
+
+/* mtd function to simulate reading byte by byte */
+static unsigned char vmu_flash_read_char(unsigned long ofs, int *retval,
+	struct mtd_info *mtd)
+{
+	struct vmu_block *vblock;
+	struct memcard *card;
+	struct mdev_part *mpart;
+	struct maple_device *mdev;
+	unsigned char *buf, ret;
+	int partition, error;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	partition = mpart->partition;
+	card = maple_get_drvdata(mdev);
+	*retval =  0;
+
+	buf = kmalloc(card->blocklen, GFP_KERNEL);
+	if (!buf) {
+		*retval = 1;
+		ret = -ENOMEM;
+		goto finish;
+	}
+
+	vblock = ofs_to_block(ofs, mtd, partition);
+	if (!vblock) {
+		*retval = 3;
+		ret = -ENOMEM;
+		goto out_buf;
+	}
+
+	error = maple_vmu_read_block(vblock->num, buf, mtd);
+	if (error) {
+		ret = error;
+		*retval = 2;
+		goto out_vblock;
+	}
+
+	ret = buf[vblock->ofs];
+
+out_vblock:
+	kfree(vblock);
+out_buf:
+	kfree(buf);
+finish:
+	return ret;
+}
+
+/* mtd higher order function to read flash */
+static int vmu_flash_read(struct mtd_info *mtd, loff_t from, size_t len,
+	size_t *retlen,  u_char *buf)
+{
+	struct maple_device *mdev;
+	struct memcard *card;
+	struct mdev_part *mpart;
+	struct vmu_cache *pcache;
+	struct vmu_block *vblock;
+	int index = 0, retval, partition, leftover, numblocks;
+	unsigned char cx;
+
+	if (len < 1)
+		return -EIO;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	partition = mpart->partition;
+	card = maple_get_drvdata(mdev);
+
+	numblocks = card->parts[partition].numblocks;
+	if (from + len > numblocks * card->blocklen)
+		len = numblocks * card->blocklen - from;
+	if (len == 0)
+		return -EIO;
+	/* Have we cached this bit already? */
+	pcache = card->parts[partition].pcache;
+	do {
+		vblock =  ofs_to_block(from + index, mtd, partition);
+		if (!vblock)
+			return -ENOMEM;
+		/* Have we cached this and is the cache valid and timely? */
+		if (pcache->valid &&
+			time_before(jiffies, pcache->jiffies_atc + HZ) &&
+			(pcache->block == vblock->num)) {
+			/* we have cached it, so do necessary copying */
+			leftover = card->blocklen - vblock->ofs;
+			if (vblock->ofs + len - index < card->blocklen) {
+				/* only a bit of this block to copy */
+				memcpy(buf + index,
+					pcache->buffer + vblock->ofs,
+					len - index);
+				index = len;
+			} else {
+				/* otherwise copy remainder of whole block */
+				memcpy(buf + index, pcache->buffer +
+					vblock->ofs, leftover);
+				index += leftover;
+			}
+		} else {
+			/*
+			* Not cached so read one byte -
+			* but cache the rest of the block
+			*/
+			cx = vmu_flash_read_char(from + index, &retval, mtd);
+			if (retval) {
+				*retlen = index;
+				kfree(vblock);
+				return cx;
+			}
+			memset(buf + index, cx, 1);
+			index++;
+		}
+		kfree(vblock);
+	} while (len > index);
+	*retlen = index;
+
+	return 0;
+}
+
+static int vmu_flash_write(struct mtd_info *mtd, loff_t to, size_t len,
+	size_t *retlen, const u_char *buf)
+{
+	struct maple_device *mdev;
+	struct memcard *card;
+	struct mdev_part *mpart;
+	int index = 0, partition, error = 0, numblocks;
+	struct vmu_cache *pcache;
+	struct vmu_block *vblock;
+	unsigned char *buffer;
+
+	mpart = mtd->priv;
+	mdev = mpart->mdev;
+	partition = mpart->partition;
+	card = maple_get_drvdata(mdev);
+
+	/* simple sanity checks */
+	if (len < 1) {
+		error = -EIO;
+		goto failed;
+	}
+	numblocks = card->parts[partition].numblocks;
+	if (to + len > numblocks * card->blocklen)
+		len = numblocks * card->blocklen - to;
+	if (len == 0) {
+		error = -EIO;
+		goto failed;
+	}
+
+	vblock = ofs_to_block(to, mtd, partition);
+	if (!vblock) {
+		error = -ENOMEM;
+		goto failed;
+	}
+
+	buffer = kmalloc(card->blocklen, GFP_KERNEL);
+	if (!buffer) {
+		error = -ENOMEM;
+		goto fail_buffer;
+	}
+
+	do {
+		/* Read in the block we are to write to */
+		error = maple_vmu_read_block(vblock->num, buffer, mtd);
+		if (error)
+			goto fail_io;
+
+		do {
+			buffer[vblock->ofs] = buf[index];
+			vblock->ofs++;
+			index++;
+			if (index >= len)
+				break;
+		} while (vblock->ofs < card->blocklen);
+
+		/* write out new buffer */
+		error = maple_vmu_write_block(vblock->num, buffer, mtd);
+		/* invalidate the cache */
+		pcache = card->parts[partition].pcache;
+		pcache->valid = 0;
+
+		if (error != card->blocklen)
+			goto fail_io;
+
+		vblock->num++;
+		vblock->ofs = 0;
+	} while (len > index);
+
+	kfree(buffer);
+	*retlen = index;
+	kfree(vblock);
+	return 0;
+
+fail_io:
+	kfree(buffer);
+fail_buffer:
+	kfree(vblock);
+failed:
+	dev_err(&mdev->dev, "VMU write failing with error %d\n", error);
+	return error;
+}
+
+static void vmu_flash_sync(struct mtd_info *mtd)
+{
+	/* Do nothing here */
+}
+
+/* Maple bus callback function to recursively query hardware details */
+static void vmu_queryblocks(struct mapleq *mq)
+{
+	struct maple_device *mdev;
+	unsigned short *res;
+	struct memcard *card;
+	__be32 partnum;
+	struct vmu_cache *pcache;
+	struct mdev_part *mpart;
+	struct mtd_info *mtd_cur;
+	struct vmupart *part_cur;
+	int error;
+
+	mdev = mq->dev;
+	card = maple_get_drvdata(mdev);
+	res = (unsigned short *) (mq->recvbuf->buf);
+	card->tempA = res[12];
+	card->tempB = res[6];
+
+	dev_info(&mdev->dev, "VMU device at partition %d has %d user "
+		"blocks with a root block at %d\n", card->partition,
+		card->tempA, card->tempB);
+
+	part_cur = &card->parts[card->partition];
+	part_cur->user_blocks = card->tempA;
+	part_cur->root_block = card->tempB;
+	part_cur->numblocks = card->tempB + 1;
+	part_cur->name = kmalloc(12, GFP_KERNEL);
+	if (!part_cur->name)
+		goto fail_name;
+
+	sprintf(part_cur->name, "vmu%d.%d.%d",
+		mdev->port, mdev->unit, card->partition);
+	mtd_cur = &card->mtd[card->partition];
+	mtd_cur->name = part_cur->name;
+	mtd_cur->type = 8;
+	mtd_cur->flags = MTD_WRITEABLE|MTD_NO_ERASE;
+	mtd_cur->size = part_cur->numblocks * card->blocklen;
+	mtd_cur->erasesize = card->blocklen;
+	mtd_cur->write = vmu_flash_write;
+	mtd_cur->read = vmu_flash_read;
+	mtd_cur->sync = vmu_flash_sync;
+	mtd_cur->writesize = card->blocklen;
+
+	mpart = kmalloc(sizeof(struct mdev_part), GFP_KERNEL);
+	if (!mpart)
+		goto fail_mpart;
+
+	mpart->mdev = mdev;
+	mpart->partition = card->partition;
+	mtd_cur->priv = mpart;
+	mtd_cur->owner = THIS_MODULE;
+
+	pcache = kzalloc(sizeof(struct vmu_cache), GFP_KERNEL);
+	if (!pcache)
+		goto fail_cache_create;
+	part_cur->pcache = pcache;
+
+	error = add_mtd_device(mtd_cur);
+	if (error)
+		goto fail_mtd_register;
+
+	maple_getcond_callback(mdev, NULL, 0,
+		MAPLE_FUNC_MEMCARD);
+
+	/*
+	* Set up a recursive call to the (probably theoretical)
+	* second or more partition
+	*/
+	if (++card->partition < card->partitions) {
+		partnum = cpu_to_be32(card->partition << 24);
+		maple_getcond_callback(mdev, vmu_queryblocks, 0,
+			MAPLE_FUNC_MEMCARD);
+		maple_add_packet(mdev, MAPLE_FUNC_MEMCARD,
+			MAPLE_COMMAND_GETMINFO, 2, &partnum);
+	}
+	return;
+
+fail_mtd_register:
+	dev_err(&mdev->dev, "Could not register maple device at (%d, %d)"
+		"error is 0x%X\n", mdev->port, mdev->unit, error);
+	for (error = 0; error <= card->partition; error++) {
+		kfree(((card->parts)[error]).pcache);
+		((card->parts)[error]).pcache = NULL;
+	}
+fail_cache_create:
+fail_mpart:
+	for (error = 0; error <= card->partition; error++) {
+		kfree(((card->mtd)[error]).priv);
+		((card->mtd)[error]).priv = NULL;
+	}
+	maple_getcond_callback(mdev, NULL, 0,
+		MAPLE_FUNC_MEMCARD);
+	kfree(part_cur->name);
+fail_name:
+	return;
+}
+
+/* Handles very basic info about the flash, queries for details */
+static int __devinit vmu_connect(struct maple_device *mdev)
+{
+	unsigned long test_flash_data, basic_flash_data;
+	int c, error;
+	struct memcard *card;
+	u32 partnum = 0;
+
+	test_flash_data = be32_to_cpu(mdev->devinfo.function);
+	/* Need to count how many bits are set - to find out which
+	 * function_data element has details of the memory card:
+	 * using Brian Kernighan's/Peter Wegner's method */
+	for (c = 0; test_flash_data; c++)
+		test_flash_data &= test_flash_data - 1;
+
+	basic_flash_data = be32_to_cpu(mdev->devinfo.function_data[c - 1]);
+
+	card = kmalloc(sizeof(struct memcard), GFP_KERNEL);
+	if (!card) {
+		error = ENOMEM;
+		goto fail_nomem;
+	}
+
+	card->partitions = (basic_flash_data >> 24 & 0xFF) + 1;
+	card->blocklen = ((basic_flash_data >> 16 & 0xFF) + 1) << 5;
+	card->writecnt = basic_flash_data >> 12 & 0xF;
+	card->readcnt = basic_flash_data >> 8 & 0xF;
+	card->removeable = basic_flash_data >> 7 & 1;
+
+	card->partition = 0;
+
+	/*
+	* Not sure there are actually any multi-partition devices in the
+	* real world, but the hardware supports them, so, so will we
+	*/
+	card->parts = kmalloc(sizeof(struct vmupart) * card->partitions,
+		GFP_KERNEL);
+	if (!card->parts) {
+		error = -ENOMEM;
+		goto fail_partitions;
+	}
+
+	card->mtd = kmalloc(sizeof(struct mtd_info) * card->partitions,
+		GFP_KERNEL);
+	if (!card->mtd) {
+		error = -ENOMEM;
+		goto fail_mtd_info;
+	}
+
+	maple_set_drvdata(mdev, card);
+
+	/*
+	* We want to trap meminfo not get cond
+	* so set interval to zero, but rely on maple bus
+	* driver to pass back the results of the meminfo
+	*/
+	maple_getcond_callback(mdev, vmu_queryblocks, 0,
+		MAPLE_FUNC_MEMCARD);
+
+	/* Make sure we are clear to go */
+	if (atomic_read(&mdev->busy) == 1) {
+		wait_event_interruptible_timeout(mdev->maple_wait,
+			atomic_read(&mdev->busy) == 0, HZ);
+		if (atomic_read(&mdev->busy) == 1) {
+			dev_notice(&mdev->dev, "VMU at (%d, %d) is busy\n",
+				mdev->port, mdev->unit);
+			error = -EAGAIN;
+			goto fail_device_busy;
+		}
+	}
+
+	atomic_set(&mdev->busy, 1);
+
+	/*
+	* Set up the minfo call: vmu_queryblocks will handle
+	* the information passed back
+	*/
+	error = maple_add_packet(mdev, MAPLE_FUNC_MEMCARD,
+		MAPLE_COMMAND_GETMINFO, 2, &partnum);
+	if (error) {
+		dev_err(&mdev->dev, "Could not lock VMU at (%d, %d)"
+			" error is 0x%X\n", mdev->port, mdev->unit, error);
+		goto fail_mtd_info;
+	}
+	return 0;
+
+fail_device_busy:
+	kfree(card->mtd);
+fail_mtd_info:
+	kfree(card->parts);
+fail_partitions:
+	kfree(card);
+fail_nomem:
+	return error;
+}
+
+static void __devexit vmu_disconnect(struct maple_device *mdev)
+{
+	struct memcard *card;
+	struct mdev_part *mpart;
+	int x;
+
+	mdev->callback = NULL;
+	card = maple_get_drvdata(mdev);
+	for (x = 0; x < card->partitions; x++) {
+		mpart = ((card->mtd)[x]).priv;
+		mpart->mdev = NULL;
+		del_mtd_device(&((card->mtd)[x]));
+		kfree(((card->parts)[x]).name);
+	}
+	kfree(card->parts);
+	kfree(card->mtd);
+	kfree(card);
+}
+
+/* Callback to handle eccentricities of both mtd subsystem
+ * and general flakyness of Dreamcast VMUs
+ */
+static int vmu_can_unload(struct maple_device *mdev)
+{
+	struct memcard *card;
+	int x;
+	struct mtd_info *mtd;
+
+	card = maple_get_drvdata(mdev);
+	for (x = 0; x < card->partitions; x++) {
+		mtd = &((card->mtd)[x]);
+		if (mtd->usecount > 0)
+			return 0;
+	}
+	return 1;
+}
+
+#define ERRSTR "VMU at (%d, %d) file error -"
+
+static void vmu_file_error(struct maple_device *mdev, void *recvbuf)
+{
+	enum maple_file_errors error = ((int *)recvbuf)[1];
+
+	switch (error) {
+
+	case MAPLE_FILEERR_INVALID_PARTITION:
+		dev_notice(&mdev->dev, ERRSTR " invalid partition number\n",
+			mdev->port, mdev->unit);
+		break;
+
+	case MAPLE_FILEERR_PHASE_ERROR:
+		dev_notice(&mdev->dev, ERRSTR " phase error\n",
+			mdev->port, mdev->unit);
+		break;
+
+	case MAPLE_FILEERR_INVALID_BLOCK:
+		dev_notice(&mdev->dev, ERRSTR " invalid block number\n",
+			mdev->port, mdev->unit);
+		break;
+
+	case MAPLE_FILEERR_WRITE_ERROR:
+		dev_notice(&mdev->dev, ERRSTR " write error\n",
+			mdev->port, mdev->unit);
+		break;
+
+	case MAPLE_FILEERR_INVALID_WRITE_LENGTH:
+		dev_notice(&mdev->dev, ERRSTR " invalid write length\n",
+			mdev->port, mdev->unit);
+		break;
+
+	case MAPLE_FILEERR_BAD_CRC:
+		dev_notice(&mdev->dev, ERRSTR " bad CRC\n",
+			mdev->port, mdev->unit);
+		break;
+
+	default:
+		dev_notice(&mdev->dev, ERRSTR " 0x%X\n",
+			mdev->port, mdev->unit, error);
+	}
+}
+
+
+static int __devinit probe_maple_vmu(struct device *dev)
+{
+	int error;
+	struct maple_device *mdev = to_maple_dev(dev);
+	struct maple_driver *mdrv = to_maple_driver(dev->driver);
+
+	mdev->can_unload = vmu_can_unload;
+	mdev->fileerr_handler = vmu_file_error;
+	mdev->driver = mdrv;
+
+	error = vmu_connect(mdev);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static int __devexit remove_maple_vmu(struct device *dev)
+{
+	struct maple_device *mdev = to_maple_dev(dev);
+
+	vmu_disconnect(mdev);
+	return 0;
+}
+
+static struct maple_driver vmu_flash_driver = {
+	.function =	MAPLE_FUNC_MEMCARD,
+	.drv = {
+		.name =		"Dreamcast_visual_memory",
+		.probe =	probe_maple_vmu,
+		.remove = 	__devexit_p(remove_maple_vmu),
+	},
+};
+
+static int __init vmu_flash_map_init(void)
+{
+	return maple_driver_register(&vmu_flash_driver);
+}
+
+static void __exit vmu_flash_map_exit(void)
+{
+	maple_driver_unregister(&vmu_flash_driver);
+}
+
+module_init(vmu_flash_map_init);
+module_exit(vmu_flash_map_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Adrian McMenamin");
+MODULE_DESCRIPTION("Flash mapping for Sega Dreamcast visual memory");