Message-Id: <20070502004557.6d61b180.akpm@linux-foundation.org>
Date:	Wed, 2 May 2007 00:45:57 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add support for Xilinx SystemACE CompactFlash
 interface.

On Wed,  2 May 2007 00:43:16 -0600 Grant Likely <grant.likely@...retlab.ca> wrote:

> Tested on Xilinx Virtex ppc405, Katmai 440SPe, and Microblaze
> 
> ...
>
> + * The SystemACE chip is designed to configure FPGAs by loading an FPGA
> + * bitstream from a file on a CF card and squirting it into FPGAs connected
> + * to the SystemACE JTAG chain.  It also has the advantage of providing an
> + * MPU interface which can be used to control the FPGA configuration process
> + * and to use the attached CF card for general purpose storage.
> + *
> + * This driver is a block device driver for the SystemACE.
> + *
> + * Initialization:
> + *    The driver registers itself as a platform_device driver at module
> + *    load time.  The platform bus will take care of calling the
> + *    ace_probe() method for all SystemACE instances in the system.  Any
> + *    number of SystemACE instances are supported.  ace_probe() calls
> + *    ace_setup() which initialized all data structures, reads the CF
> + *    id structure and registers the device.
> + *
> + * Processing:
> + *    Just about all of the heavy lifting in this driver is performed by
> + *    a Finite State Machine (FSM).  The driver needs to wait on a number
> + *    of events; some raised by interrupts, some which need to be polled
> + *    for.  Describing all of the behaviour in a FSM seems to be the
> + *    easiest way to keep the complexity low and make it easy to
> + *    understand what the driver is doing.  If the block ops or the
> + *    request function need to interact with the hardware, then they
> + *    simply need to flag the request and kick of FSM processing.
> + *
> + *    The FSM itself is atomic-safe code which can be run from any
> + *    context.  The general process flow is:
> + *    1. obtain the ace->lock spinlock.
> + *    2. loop on ace_fsm_dostate() until the ace->fsm_continue flag is
> + *       cleared.
> + *    3. release the lock.
> + *
> + *    Individual states do not sleep in any way.  If a condition needs to
> + *    be waited for then the state much clear the fsm_continue flag and
> + *    either schedule the FSM to be run again at a later time, or expect
> + *    an interrupt to call the FSM when the desired condition is met.
> + *
> + *    In normal operation, the FSM is processed at interrupt context
> + *    either when the driver's tasklet is scheduled, or when an irq is
> + *    raised by the hardware.  The tasklet can be scheduled at any time.
> + *    The request method in particular schedules the tasklet when a new
> + *    request has been indicated by the block layer.  Once started, the
> + *    FSM proceeds as far as it can processing the request until it
> + *    needs on a hardware event.  At this point, it must yield execution.
> + *
> + *    A state has two options when yielding execution:
> + *    1. ace_fsm_yield()
> + *       - Call if need to poll for event.
> + *       - clears the fsm_continue flag to exit the processing loop
> + *       - reschedules the tasklet to run again as soon as possible
> + *    2. ace_fsm_yieldirq()
> + *       - Call if an irq is expected from the HW
> + *       - clears the fsm_continue flag to exit the processing loop
> + *       - does not reschedule the tasklet so the FSM will not be processed
> + *         again until an irq is received.
> + *    After calling a yield function, the state must return control back
> + *    to the FSM main loop.
> + *
> + *    Additionally, the driver maintains a kernel timer which can process
> + *    the FSM.  If the FSM gets stalled, typically due to a missed
> + *    interrupt, then the kernel timer will expire and the driver can
> + *    continue where it left off.
> + *
> + * To Do:
> + *    - Add FPGA configuration control interface.
> + *    - Request major number from lanana
> + *    - Add legacy device geometry ioctl
> + */

Swoon.  Want a job writing kernel comments?

>
> ...
>
> +static LIST_HEAD(ace_instances);
> +static int ace_major = 0;

Pleas eremove the "= 0;': it takes up space in vmlinux, but .bss is zeroed
anyway.

> +
> +/* ---------------------------------------------------------------------
> + * Low level register access
> + */
> +
> +struct ace_reg_ops {
> +	uint16_t (*in)(struct ace_device *ace, ulong reg);

The driver uses a strange mixture of uintNN_t and ulong.  One would at
least expect uint16_t and uint32_t.

u16 is preferred over uint16_t.

And if you really meant plain old unsigned long, please use "unsigned
long", not ulong.

This affects the whole patch.

> +	void (*out)(struct ace_device *ace, ulong reg, uint16_t val);
> +	void (*identin)(struct ace_device *ace);
> +	void (*datain)(struct ace_device *ace);
> +	void (*dataout)(struct ace_device *ace);
> +};
> +
> +/* 8 Bit bus width */
> +static uint16_t ace_in_8(struct ace_device *ace, ulong reg)

Here we have the correct `foo *bar';

> +{
> +	void* r = ace->baseaddr + reg;

And here we have the kernelly-incorrect `foo* bar;'

Please do s/* / */ everywhere.

> +	return in_8(r) | (in_8(r+1) << 8);
> +}
> +
> +static void ace_out_8(struct ace_device *ace, ulong reg, uint16_t val)
> +{
> +	void* r = ace->baseaddr + reg;
> +	out_8(r, val);
> +	out_8(r+1, val >> 8);
> +}
> +
> +static void ace_identin_8(struct ace_device *ace)
> +{
> +	void* r = ace->baseaddr + 0x40;
> +	int i = ACE_FIFO_SIZE/2;
> +	while (i--)
> +#if defined(__BIG_ENDIAN)
> +		*ace->data_ptr++ = (in_8(r)) | (in_8(r+1)<<8);
> +#else
> +		*ace->data_ptr++ = (in_8(r)<<8) | (in_8(r+1));
> +#endif
> +}

This ifdeffery appears in several places.  SUggest the addition of a helper
function which does it in a single place.

> +static void ace_datain_8(struct ace_device *ace)
> +{
> +	void* r = ace->baseaddr + 0x40;
> +	int i = ACE_FIFO_SIZE/2;
> +	while (i--)
> +#if defined(__BIG_ENDIAN)
> +		*ace->data_ptr++ = (in_8(r)<<8) | (in_8(r+1));
> +#else
> +		*ace->data_ptr++ = (in_8(r)) | (in_8(r+1)<<8);
> +#endif
> +}
> +
> +static void ace_dataout_8(struct ace_device *ace)
> +{
> +	void* r = ace->baseaddr + 0x40;
> +	int i = ACE_FIFO_SIZE/2;
> +	while (i--) {
> +#if defined(__BIG_ENDIAN)
> +		out_8(r, *ace->data_ptr >> 8);
> +		out_8(r+1, *ace->data_ptr);
> +#else
> +		out_8(r, *ace->data_ptr);
> +		out_8(r+1, *ace->data_ptr >> 8);
> +#endif

Ditto here if poss.

> +		ace->data_ptr++;
> +	}
> +}
> +
> 
> ...
>
> +
> +#define ace_in(ace, reg)		ace->reg_ops->in(ace, reg)
> +static inline uint32_t ace_in32(struct ace_device *ace, ulong reg)
> +{
> +	return ace_in(ace, reg) | (ace_in(ace, reg+2) << 16);
> +}
> +#define ace_out(ace, reg, val)		ace->reg_ops->out(ace, reg, val)
> +static inline void ace_out32(struct ace_device *ace, ulong reg, uint32_t val)
> +{
> +	ace_out(ace, reg, val);
> +	ace_out(ace, reg+2, val >> 16);
> +}
> +#define ace_identin(ace)		ace->reg_ops->identin(ace)
> +#define ace_datain(ace)			ace->reg_ops->datain(ace)
> +#define ace_dataout(ace)		ace->reg_ops->dataout(ace)

inline functions are preferred.  The above is a strange mixture of inlines
and macros.  Can they all be made inlines?

> +/* legacy macros, to be removed */
> +#define ace_reg_read16(ace, reg)	ace_in(ace, reg)
> +#define ace_reg_read32(ace, reg)	ace_in32(ace, reg)
> +#define ace_reg_write16(ace, reg, val)	ace_out(ace, reg, val)
> +#define ace_reg_write32(ace, reg, val)	ace_out32(ace, reg, val)

Can they be removed now?

> +/* ---------------------------------------------------------------------
> + * Debug support functions
> + */
> +
> +#define ace_dbg(ace, format, arg...) dev_dbg(ace->dev, format, ## arg)
> +#define ace_err(ace, format, arg...) dev_err(ace->dev, format, ## arg)
> +#define ace_info(ace, format, arg...) dev_info(ace->dev, format, ## arg)
> +#define ace_warn(ace, format, arg...) dev_warn(ace->dev, format, ## arg)
> +#define ace_notice(ace, format, arg...) dev_notice(ace->dev, format, ## arg)

It would be preferred if these were simply removed - open-code dev_foo()
everywhere.

> +#if defined(DEBUG)
> +static void ace_dump_mem(void* base, int len)
> +{
> +	const char* ptr = base;
> +	int i, j;
> +
> +	for (i = 0; i < len; i += 16) {
> +		printk(KERN_INFO "%.8x:", i);
> +		for (j = 0; j < 16; j++) {
> +			if (!(j % 4))
> +				printk(" ");
> +			printk("%.2x", ptr[i+j]);
> +		}
> +		printk(" ");
> +		for (j = 0; j < 16; j++)
> +			printk("%c", isprint(ptr[i+j]) ? ptr[i+j] : '.');
> +		printk("\n");
> +	}
> +}
> +#else
> +static inline void ace_dump_mem(void* base, int len) {}
> +#endif

Heh, that'll be our ninth hexdump implementation.

Don't worry about it for now.  Soon we'll hopefully have a lib/hexdump.c.

> +static void ace_dump_regs(struct ace_device *ace)
> +{
> +	ace_info(ace, "    ctrl:  %.8x  seccnt/cmd: %.4x      ver:%.4x\n"
> +	              "    status:%.8x  mpu_lba:%.8x  busmode:%4x\n"
> +	              "    error: %.8x  cfg_lba:%.8x  fatstat:%.4x\n",
> +	         ace_reg_read32(ace, ACE_CTRL),
> +	         ace_reg_read16(ace, ACE_SECCNTCMD),
> +	         ace_reg_read16(ace, ACE_VERSION),
> +	         ace_reg_read32(ace, ACE_STATUS),
> +	         ace_reg_read32(ace, ACE_MPULBA),
> +	         ace_reg_read16(ace, ACE_BUSMODE),
> +	         ace_reg_read32(ace, ACE_ERROR),
> +	         ace_reg_read32(ace, ACE_CFGLBA),
> +	         ace_reg_read16(ace, ACE_FATSTAT));
> +}
> +
> +void ace_fix_driveid (struct hd_driveid *id)

No space before the "(", please.

> +{
> +#ifndef __LITTLE_ENDIAN
> +# ifdef __BIG_ENDIAN
> +	/* The ace_reg_read16 macro handles 16 bit reads correctly, but
> +	 * 32bit values are partially little endian; swap the words
> +	 */
> +	id->lba_capacity   = ((id->lba_capacity >> 16) & 0x0000FFFF) |
> +	                     ((id->lba_capacity << 16) & 0xFFFF0000);
> +	id->spg            = ((id->spg >> 16) & 0x0000FFFF) |
> +	                     ((id->spg << 16) & 0xFFFF0000);
> +# else
> +#  error "Please fix <asm/byteorder.h>"

Don't you trust us? :)

> +# endif
> +#endif
> +}
> +
> +/* ---------------------------------------------------------------------
> + * Finite State Machine (FSM) implementation
> + */
> +
> +/* FSM tasks; used to direct state transitions */
> +#define ACE_TASK_IDLE      0
> +#define ACE_TASK_IDENTIFY  1
> +#define ACE_TASK_READ      2
> +#define ACE_TASK_WRITE     3
> +#define ACE_FSM_NUM_TASKS  4
> +
> +/* FSM state definitions */
> +#define ACE_FSM_STATE_IDLE               0
> +#define ACE_FSM_STATE_REQ_LOCK           1
> +#define ACE_FSM_STATE_WAIT_LOCK          2
> +#define ACE_FSM_STATE_WAIT_CFREADY       3
> +#define ACE_FSM_STATE_IDENTIFY_PREPARE   4
> +#define ACE_FSM_STATE_IDENTIFY_TRANSFER  5
> +#define ACE_FSM_STATE_IDENTIFY_COMPLETE  6
> +#define ACE_FSM_STATE_REQ_PREPARE        7
> +#define ACE_FSM_STATE_REQ_TRANSFER       8
> +#define ACE_FSM_STATE_REQ_COMPLETE       9
> +#define ACE_FSM_STATE_ERROR             10
> +#define ACE_FSM_NUM_STATES              11
> +
> +#if defined(DEBUG)
> +const char* ace_statenames[ACE_FSM_NUM_STATES] = {
> +	"idle",
> +	"req lock",
> +	"wait lock",
> +	"wait cf ready",
> +	"identify prepare",
> +	"identify transfer",
> +	"identify complete",
> +	"request prepare",
> +	"request transfer",
> +	"request complete",
> +};
> +#endif

Can these have static storage class?

> +/* Set flag to exit FSM loop and reschedule tasklet */
> +static void inline ace_fsm_yield(struct ace_device *ace)
> +{
> +	ace_dbg(ace, "ace_fsm_yield()\n");
> +	tasklet_schedule(&ace->fsm_tasklet);
> +	ace->fsm_continue_flag = 0;
> +}

Kernel typically uses "static inline void", not "static void inline"
(please review the whole patchset).

> +/* Set flag to exit FSM loop and wait for IRQ to reschedule tasklet */
> +static void inline ace_fsm_yieldirq(struct ace_device *ace)
> +{
> +	ace_dbg(ace, "ace_fsm_yieldirq()\n");
> +	ace->fsm_continue_flag = 0;
> +}
> +
> +/* Get the next read/write request; ending requests that we don't handle */
> +struct request* ace_get_next_request(request_queue_t *q)

struct request *ace_get_next_request

> +{
> +	struct request *req;
> +
> +	while ((req = elv_next_request(q)) != NULL) {
> +		if (blk_fs_request(req))
> +			break;
> +		end_request(req, 0);
> +	}
> +	return req;
> +}
> +
> +static void ace_fsm_dostate(struct ace_device *ace)
> +{
> +	struct request *req;
> +	uint32_t status;
> +	uint16_t val;
> +	int count;
> +	int i;
> +
> +#if defined(DEBUG)
> +	const char *name = "invalid";
> +	if (ace->fsm_state < ACE_FSM_NUM_STATES)
> +		name = ace_statenames[ace->fsm_state];
> +	ace_info(ace, "fsm_state=%i \"%s\", id_req_count=%i\n",
> +	         ace->fsm_state, name, ace->id_req_count);
> +#endif
> +
> +	switch (ace->fsm_state) {
> +	    case ACE_FSM_STATE_IDLE:

Please lose the four-spaces and line the `case' up with the `switch'.

> +		/* See if there is anything to do */
> +		if (ace->id_req_count || ace_get_next_request(ace->queue)) {
> +			ace->fsm_iter_num++;
> +			ace->fsm_state = ACE_FSM_STATE_REQ_LOCK;
> +			mod_timer(&ace->stall_timer, jiffies + HZ);
> +			if (!timer_pending(&ace->stall_timer))
> +				add_timer(&ace->stall_timer);
> +			break;
> +		}
> +		del_timer(&ace->stall_timer);
> +		ace->fsm_continue_flag = 0;
> +		break;
> +
>
> ...
>
> +
> +static void ace_fsm_tasklet(ulong data)
> +{
> +	struct ace_device *ace = (void*)data;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&ace->lock, flags);
> +
> +	/* Loop over state machine until told to stop */
> +	ace->fsm_continue_flag = 1;
> +	while (ace->fsm_continue_flag)
> +		ace_fsm_dostate(ace);
> +
> +	spin_unlock_irqrestore(&ace->lock, flags);
> +}
> +
> +static void ace_stall_timer(ulong data)
> +{
> +	struct ace_device *ace = (void*)data;
> +	unsigned long flags;
> +
> +	ace_warn(ace, "kicking stalled fsm; state=%i task=%i iter=%i dc=%i\n",
> +	         ace->fsm_state, ace->fsm_task, ace->fsm_iter_num,
> +	         ace->data_count);
> +	spin_lock_irqsave(&ace->lock, flags);
> +
> +	/* Loop over state machine until told to stop */
> +	ace->fsm_continue_flag = 1;
> +	while (ace->fsm_continue_flag)
> +		ace_fsm_dostate(ace);
> +
> +	/* Rearm the stall timer */
> +	ace->stall_timer.expires = jiffies + HZ;
> +	add_timer(&ace->stall_timer);

mod_timer() would work here.

> +	spin_unlock_irqrestore(&ace->lock, flags);
> +}
> +
> +/* ---------------------------------------------------------------------
> + * Interrupt handling routines
> + */
> +static int ace_interrupt_checkstate(struct ace_device *ace)
> +{
> +	uint32_t sreg = ace_reg_read32(ace, ACE_STATUS);
> +	uint16_t creg = ace_reg_read16(ace, ACE_CTRL);
> +
> +	/* Check for error occurance */
> +	if ((sreg & (ACE_STATUS_CFGERROR | ACE_STATUS_CFCERROR)) &&
> +	    (creg & ACE_CTRL_ERRORIRQ)) {
> +		ace_err(ace, "transfer failure\n");
> +		ace_dump_regs(ace);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static irqreturn_t ace_interrupt(int irq, void *dev_id)
> +{
> +	uint16_t creg;
> +	struct ace_device *ace = dev_id;
> +	unsigned long flags;
> +
> +	/* be safe and get the lock */
> +	spin_lock_irqsave(&ace->lock, flags);

Normally a bare spin_lock() suffices in the interrupt handler: we won't be
taking any interrupts on this CPU on behalf of this device while running
this function.

> +	ace->in_irq = 1;
> +
> +	/* clear the interrupt */
> +	creg = ace_reg_read16(ace, ACE_CTRL);
> +	ace_reg_write16(ace, ACE_CTRL, creg | ACE_CTRL_RESETIRQ);
> +	ace_reg_write16(ace, ACE_CTRL, creg);
> +
> +	/* check for IO failures */
> +	if (ace_interrupt_checkstate(ace))
> +		ace->data_result = -EIO;
> +
> +	if (ace->fsm_task == 0) {
> +		ace_err(ace, "spurious irq; stat=%.8x ctrl=%.8x cmd=%.4x\n",
> +		        ace_reg_read32(ace, ACE_STATUS),
> +		        ace_reg_read32(ace, ACE_CTRL),
> +		        ace_reg_read16(ace, ACE_SECCNTCMD));
> +		ace_err(ace, "fsm_task=%i fsm_state=%i data_count=%i\n",
> +		        ace->fsm_task, ace->fsm_state, ace->data_count);
> +	}
> +
> +	/* Loop over state machine until told to stop */
> +	ace->fsm_continue_flag = 1;
> +	while (ace->fsm_continue_flag)
> +		ace_fsm_dostate(ace);
> +
> +	/* done with interrupt; drop the lock */
> +	ace->in_irq = 0;
> +	spin_unlock_irqrestore(&ace->lock, flags);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/* ---------------------------------------------------------------------
> + * Block ops
> + */
> +static void ace_request(request_queue_t *q)
> +{
> +	struct request *req;
> +	struct ace_device *ace;
> +
> +	req = ace_get_next_request(q);
> +
> +	if (req) {
> +		ace = req->rq_disk->private_data;
> +		tasklet_schedule(&ace->fsm_tasklet);
> +	}
> +}
> +
> +static int ace_media_changed(struct gendisk *gd)
> +{
> +	struct ace_device *ace = gd->private_data;
> +	ace_dbg(ace, "ace_media_changed(): %i\n", ace->media_change);
> +
> +	return ace->media_change;
> +}
> +
> +static int ace_revalidate_disk(struct gendisk *gd)
> +{
> +	struct ace_device *ace = gd->private_data;
> +	ulong flags;
> +
> +	ace_dbg(ace, "ace_revalidate_disk()\n");
> +
> +	if (ace->media_change) {
> +		ace_dbg(ace, "requesting cf id and scheduling tasklet\n");
> +
> +		spin_lock_irqsave(&ace->lock, flags);
> +		ace->id_req_count++;
> +		spin_unlock_irqrestore(&ace->lock, flags);
> +
> +		tasklet_schedule(&ace->fsm_tasklet);
> +		wait_for_completion(&ace->id_completion);
> +	}
> +
> +	ace_dbg(ace, "revalidate complete\n");
> +	return ace->id_result;
> +}
> +
> +static int ace_open(struct inode *inode, struct file *filp)
> +{
> +	struct ace_device *ace = inode->i_bdev->bd_disk->private_data;
> +	unsigned long flags;
> +
> +	ace_dbg(ace, "ace_open() users=%i\n", ace->users+1);
> +
> +	filp->private_data = ace;
> +	spin_lock_irqsave(&ace->lock, flags);
> +	ace->users++;
> +	spin_unlock_irqrestore(&ace->lock, flags);
> +
> +	check_disk_change(inode->i_bdev);
> +	return 0;
> +}

hm, there are a few fields (users, in_irq) which are purely for debug
support.  Fair enough, I guess.

> +static int ace_release(struct inode *inode, struct file *filp)
> +{
> +	struct ace_device *ace = inode->i_bdev->bd_disk->private_data;
> +	unsigned long flags;
> +	uint16_t val;
> +
> +	ace_dbg(ace, "ace_release() users=%i\n", ace->users-1);
> +
> +	spin_lock_irqsave(&ace->lock, flags);
> +	ace->users--;
> +	if (ace->users == 0) {
> +		val = ace_reg_read16(ace, ACE_CTRL);
> +		ace_reg_write16(ace, ACE_CTRL, val & ~ACE_CTRL_LOCKREQ);
> +	}
> +	spin_unlock_irqrestore(&ace->lock, flags);
> +	return 0;
> +}

Who owns gendisk.private_data?  Is it the device driver?  I've never
looked...

> +static int ace_ioctl(struct inode *inode, struct file *filp,
> +                         unsigned int cmd, unsigned long arg)
> +{
> +	struct ace_device *ace = inode->i_bdev->bd_disk->private_data;
> +	ace_dbg(ace, "ace_ioctl()\n");
> +
> +	return -ENOTTY;
> +}

I suspect you can just leave this unimplemented.

> +static struct block_device_operations ace_fops = {
> +	.owner = THIS_MODULE,
> +	.open = ace_open,
> +	.release = ace_release,
> +	.media_changed = ace_media_changed,
> +	.revalidate_disk = ace_revalidate_disk,
> +	.ioctl = ace_ioctl,
> +};
> +
> +/* --------------------------------------------------------------------
> + * SystemACE device setup/teardown code
> + */
> +static int ace_setup(struct ace_device *ace)
> +{
> +	uint16_t version;
> +	uint16_t val;
> +	int rc;
> +
> +	spin_lock_init(&ace->lock);
> +	init_completion(&ace->id_completion);
> +
> +	/*
> +	 * Map the device
> +	 */
> +	ace->baseaddr = ioremap(ace->physaddr, 0x80);
> +	if (!ace->baseaddr)
> +		goto err_ioremap;
> +
> +	if (ace->irq != NO_IRQ) {
> +		rc = request_irq(ace->irq, ace_interrupt, 0, "systemace", ace);
> +		if (rc) {
> +			/* Failure - fall back to polled mode */
> +			ace_err(ace, "request_irq failed\n");
> +			ace->irq = NO_IRQ;
> +		}
> +	}
> +
> +	/*
> +	 * Initialize the state machine tasklet and stall timer
> +	 */
> +	tasklet_init(&ace->fsm_tasklet, ace_fsm_tasklet, (ulong)ace);
> +	init_timer(&ace->stall_timer);
> +	ace->stall_timer.function = ace_stall_timer;
> +	ace->stall_timer.data = (ulong)ace;

setup_timer()?

> +	/*
> +	 * Initialize the request queue
> +	 */
> +	ace->queue = blk_init_queue(ace_request, &ace->lock);
> +	if (ace->queue == NULL)
> +		goto err_blk_initq;
> +	blk_queue_hardsect_size(ace->queue, 512);
> +
> +	/*
> +	 * Allocate and initialize GD structure
> +	 */
> +	ace->gd = alloc_disk(ACE_NUM_MINORS);
> +	if (!ace->gd)
> +		goto err_alloc_disk;
> +
> +	ace->gd->major = ace_major;
> +	ace->gd->first_minor = ace->id * ACE_NUM_MINORS;
> +	ace->gd->fops = &ace_fops;
> +	ace->gd->queue = ace->queue;
> +	ace->gd->private_data = ace;
> +	snprintf(ace->gd->disk_name, 32, "xs%c", ace->id + 'a');
> +	device_rename(ace->dev, ace->gd->disk_name);

Now why are we doing a device_rename() here?  The only other caller in the
tree is the netdev renaming code.  I suspect something is awry here.

> +	/* set bus width */
> +	if (ace->bus_width == 1) {
> +		/* 0x0101 should work regardless of endianess */
> +		ace_out_le16(ace, ACE_BUSMODE, 0x0101);
> +
> +		/* read it back to determine endianess */
> +		if (ace_in_le16(ace, ACE_BUSMODE) == 0x0001)
> +			ace->reg_ops = &ace_reg_le16_ops;
> +		else
> +			ace->reg_ops = &ace_reg_be16_ops;
> +	} else {
> +		ace_out_8(ace, ACE_BUSMODE, 0x00);
> +		ace->reg_ops = &ace_reg_8_ops;
> +	}
> +
> +	/* Make sure version register is sane */
> +	version = ace_reg_read16(ace, ACE_VERSION);
> +	if ((version == 0) || (version == 0xFFFF))
> +		goto err_read;
> +
> +	/* Put sysace in a sane state by clearing most control reg bits */
> +	ace_reg_write16(ace, ACE_CTRL, ACE_CTRL_FORCECFGMODE |
> +	                               ACE_CTRL_DATABUFRDYIRQ |
> +	                               ACE_CTRL_ERRORIRQ);
> +
> +	/* Enable interrupts */
> +	val = ace_reg_read16(ace, ACE_CTRL);
> +	val |= ACE_CTRL_DATABUFRDYIRQ | ACE_CTRL_ERRORIRQ;
> +	ace_reg_write16(ace, ACE_CTRL, val);
> +
> +	/* Print the identification */
> +	ace_info(ace, "Xilinx SystemACE revision %i.%i.%i\n",
> +	         (version>>12)&0xf, (version>>8)&0x0f, version&0xff);
> +	ace_dbg(ace, "physaddr 0x%lx, mapped to 0x%p, irq=%i\n",
> +	        ace->physaddr, ace->baseaddr, ace->irq);
> +
> +	ace->media_change = 1;
> +	ace_revalidate_disk(ace->gd);
> +
> +	/* Make the sysace device 'live' */
> +	list_add(&ace->list, &ace_instances);

No locking needed here?

There is no list_del() in this patch.  Fortunately, ace_instances is
otherwise unused.  If it was used, it would crash.

> +	add_disk(ace->gd);
> +
> +	return 0;
> +
> +err_read:
> +	put_disk(ace->gd);
> +err_alloc_disk:
> +	blk_cleanup_queue(ace->queue);
> +err_blk_initq:
> +	iounmap(ace->baseaddr);
> +	if (ace->irq != NO_IRQ)
> +		free_irq(ace->irq, ace);
> +err_ioremap:
> +	printk(KERN_INFO "xsysace: error initializing device at 0x%lx\n",
> +	      ace->physaddr);
> +	return -ENOMEM;
> +}
> +
> +static void ace_teardown(struct ace_device *ace)
> +{
> +	if (ace->gd) {
> +		del_gendisk(ace->gd);
> +		put_disk(ace->gd);
> +	}
> +
> +	if (ace->queue)
> +		blk_cleanup_queue(ace->queue);
> +
> +	tasklet_kill(&ace->fsm_tasklet);
> +
> +	if (ace->irq != NO_IRQ)
> +		free_irq(ace->irq, ace);
> +
> +	iounmap(ace->baseaddr);
> +}
> +
> +/* ---------------------------------------------------------------------
> + * Platform Bus Support
> + */
> +
> +static int ace_probe(struct device *device)
> +{
> +	struct platform_device *dev = to_platform_device(device);
> +	struct ace_device *ace;
> +	int i;
> +
> +	dev_dbg(device, "ace_probe(%p)\n", device);
> +
> +	/*
> +	 * Allocate the ace device structure
> +	 */
> +	ace = kmalloc(sizeof(struct ace_device), GFP_KERNEL);
> +	if (!ace)
> +		goto err_alloc;
> +	memset(ace, 0, sizeof(struct ace_device));

kzalloc()

> +	ace->dev = device;
> +	ace->id = dev->id;
> +	ace->irq = NO_IRQ;
> +
> +	for (i = 0; i < dev->num_resources; i++) {
> +		if (dev->resource[i].flags & IORESOURCE_MEM)
> +			ace->physaddr = dev->resource[i].start;
> +		if (dev->resource[i].flags & IORESOURCE_IRQ)
> +			ace->irq = dev->resource[i].start;
> +	}
> +	
> +	/* FIXME: Should get bus_width from the platform_device struct */
> +	ace->bus_width = 1;
> +
> +	dev_set_drvdata(&dev->dev, ace);
> +
> +	/* Call the bus-independant setup code */
> +	if (ace_setup(ace) != 0)
> +		goto err_setup;
> +
> +	return 0;
> +
> +err_setup:
> +	dev_set_drvdata(&dev->dev, NULL);
> +	kfree(ace);
> +err_alloc:
> +	printk(KERN_ERR "xsysace: could not initialize device\n");
> +	return -ENOMEM;
> +}
> +
> +/*
> + * Platform bus remove() method
> + */
> +static int ace_remove(struct device *device)
> +{
> +	struct ace_device *ace = dev_get_drvdata(device);
> +
> +	dev_dbg(device, "ace_remove(%p)\n", device);
> +
> +	if (ace) {
> +		ace_teardown(ace);
> +		kfree(ace);
> +	}
> +
> +	return 0;
> +}
> +
> +static struct device_driver ace_driver = {
> +	.name	= "xsysace",
> +	.bus	= &platform_bus_type,
> +	.probe	= ace_probe,
> +	.remove	= ace_remove,
> +};

Should .remove be __devexit_p?  The driver is perhaps using the
space-saving __devexit and __devinit less than it should.

> +/* ---------------------------------------------------------------------
> + * Module init/exit routines
> + */
> +static int __init ace_init(void)
> +{
> +	ace_major = register_blkdev(ace_major, "xsysace");
> +	if (ace_major <= 0) {
> +		printk(KERN_WARNING "xsysace: register_blkdev() failed\n");
> +		return ace_major;
> +	}
> +
> +	pr_debug("Registering Xilinx SystemACE driver, major=%i\n", ace_major);
> +	return driver_register(&ace_driver);
> +}
> +
> +static void __exit ace_exit(void)
> +{
> +	pr_debug("Unregistering Xilinx SystemACE driver\n");
> +	driver_unregister(&ace_driver);
> +	if (unregister_blkdev(ace_major, "xsysace"))
> +		printk(KERN_WARNING "systemace unregister_blkdev(%i) failed\n",
> +		       ace_major);
> +}
> +
> +module_init(ace_init);
> +module_exit(ace_exit);

Looks nice though.
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