staging: fwserial: Add TTY-over-Firewire serial driver

This patch provides the kernel driver for high-speed TTY
communication over the IEEE 1394 bus.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Kconfig

@@ -140,4 +140,6 @@ source "drivers/staging/imx-drm/Kconfig"
 
 source "drivers/staging/dgrp/Kconfig"
 
+source "drivers/staging/fwserial/Kconfig"
+
 endif # STAGING

drivers/staging/Makefile

@@ -62,3 +62,4 @@ obj-$(CONFIG_NET_VENDOR_SILICOM)	+= silicom/
 obj-$(CONFIG_CED1401)		+= ced1401/
 obj-$(CONFIG_DRM_IMX)		+= imx-drm/
 obj-$(CONFIG_DGRP)		+= dgrp/
+obj-$(CONFIG_FIREWIRE_SERIAL)	+= fwserial/

drivers/staging/fwserial/Kconfig

+config FIREWIRE_SERIAL
+       tristate "TTY over Firewire"
+       depends on FIREWIRE
+       help
+          This enables TTY over IEEE 1394, providing high-speed serial
+	  connectivity to cabled peers.
+
+	  To compile this driver as a module, say M here:  the module will
+	  be called firewire-serial.

drivers/staging/fwserial/Makefile

+obj-$(CONFIG_FIREWIRE_SERIAL) += firewire-serial.o
+firewire-serial-objs := fwserial.o dma_fifo.o

drivers/staging/fwserial/TODO

+TODOs
+-----
+1. Implement retries for RCODE_BUSY, RCODE_NO_ACK and RCODE_SEND_ERROR
+   - I/O is handled asynchronously which presents some issues when error
+     conditions occur.
+2. Implement _robust_ console on top of this. The existing prototype console
+   driver is not ready for the big leagues yet.
+3. Expose means of controlling attach/detach of peers via sysfs. Include
+   GUID-to-port matching/whitelist/blacklist.
+
+-- Issues with firewire stack --
+1. This driver uses the same unregistered vendor id that the firewire core does
+     (0xd00d1e). Perhaps this could be exposed as a define in
+     firewire-constants.h?
+2. MAX_ASYNC_PAYLOAD needs to be publicly exposed by core/ohci
+   - otherwise how will this driver know the max size of address window to
+     open for one packet write?
+3. Maybe device_max_receive() and link_speed_to_max_payload() should be
+     taken up by the firewire core?
+4. To avoid dropping rx data while still limiting the maximum buffering,
+     the size of the AR context must be known. How to expose this to drivers?
+5. Explore if bigger AR context will reduce RCODE_BUSY responses
+   (or auto-grow to certain max size -- but this would require major surgery
+    as the current AR is contiguously mapped)
+
+-- Issues with TTY core --
+  1. Hack for alternate device name scheme
+     - because udev no longer allows device renaming, devices should have
+       their proper names on creation. This is an issue for creating the
+       fwloop<n> device with the fwtty<n> devices because although duplicating
+       roughly the same operations as tty_port_register_device() isn't difficult,
+       access to the tty_class & tty_fops is restricted in scope.
+
+       This is currently being worked around in create_loop_device() by
+       extracting the tty_class ptr and tty_fops ptr from the previously created
+       tty devices. Perhaps an add'l api can be added -- eg.,
+       tty_{port_}register_named_device().

drivers/staging/fwserial/dma_fifo.c

+/*
+ * DMA-able FIFO implementation
+ *
+ * Copyright (C) 2012 Peter Hurley <peter@hurleysoftware.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/bug.h>
+
+#include "dma_fifo.h"
+
+#ifdef DEBUG_TRACING
+#define df_trace(s, args...) pr_debug(s, ##args)
+#else
+#define df_trace(s, args...)
+#endif
+
+#define FAIL(fifo, condition, format...) ({				\
+	fifo->corrupt = !!(condition);					\
+	if (unlikely(fifo->corrupt)) {					\
+		__WARN_printf(format);					\
+	}								\
+	unlikely(fifo->corrupt);					\
+})
+
+/*
+ * private helper fn to determine if check is in open interval (lo,hi)
+ */
+static bool addr_check(unsigned check, unsigned lo, unsigned hi)
+{
+	return check - (lo + 1) < (hi - 1) - lo;
+}
+
+/**
+ * dma_fifo_init: initialize the fifo to a valid but inoperative state
+ * @fifo: address of in-place "struct dma_fifo" object
+ */
+void dma_fifo_init(struct dma_fifo *fifo)
+{
+	memset(fifo, 0, sizeof(*fifo));
+	INIT_LIST_HEAD(&fifo->pending);
+}
+
+/**
+ * dma_fifo_alloc - initialize and allocate dma_fifo
+ * @fifo: address of in-place "struct dma_fifo" object
+ * @size: 'apparent' size, in bytes, of fifo
+ * @align: dma alignment to maintain (should be at least cpu cache alignment),
+ *         must be power of 2
+ * @tx_limit: maximum # of bytes transmissable per dma (rounded down to
+ *            multiple of alignment, but at least align size)
+ * @open_limit: maximum # of outstanding dma transactions allowed
+ * @gfp_mask: get_free_pages mask, passed to kmalloc()
+ *
+ * The 'apparent' size will be rounded up to next greater aligned size.
+ * Returns 0 if no error, otherwise an error code
+ */
+int dma_fifo_alloc(struct dma_fifo *fifo, int size, unsigned align,
+		   int tx_limit, int open_limit, gfp_t gfp_mask)
+{
+	int capacity;
+
+	if (!is_power_of_2(align) || size < 0)
+		return -EINVAL;
+
+	size = round_up(size, align);
+	capacity = size + align * open_limit + align * DMA_FIFO_GUARD;
+	fifo->data = kmalloc(capacity, gfp_mask);
+	if (!fifo->data)
+		return -ENOMEM;
+
+	fifo->in = 0;
+	fifo->out = 0;
+	fifo->done = 0;
+	fifo->size = size;
+	fifo->avail = size;
+	fifo->align = align;
+	fifo->tx_limit = max_t(int, round_down(tx_limit, align), align);
+	fifo->open = 0;
+	fifo->open_limit = open_limit;
+	fifo->guard = size + align * open_limit;
+	fifo->capacity = capacity;
+	fifo->corrupt = 0;
+
+	return 0;
+}
+
+/**
+ * dma_fifo_free - frees the fifo
+ * @fifo: address of in-place "struct dma_fifo" to free
+ *
+ * Also reinits the fifo to a valid but inoperative state. This
+ * allows the fifo to be reused with a different target requiring
+ * different fifo parameters.
+ */
+void dma_fifo_free(struct dma_fifo *fifo)
+{
+	struct dma_pending *pending, *next;
+
+	if (fifo->data == NULL)
+		return;
+
+	list_for_each_entry_safe(pending, next, &fifo->pending, link)
+		list_del_init(&pending->link);
+	kfree(fifo->data);
+	fifo->data = NULL;
+}
+
+/**
+ * dma_fifo_reset - dumps the fifo contents and reinits for reuse
+ * @fifo: address of in-place "struct dma_fifo" to reset
+ */
+void dma_fifo_reset(struct dma_fifo *fifo)
+{
+	struct dma_pending *pending, *next;
+
+	if (fifo->data == NULL)
+		return;
+
+	list_for_each_entry_safe(pending, next, &fifo->pending, link)
+		list_del_init(&pending->link);
+	fifo->in = 0;
+	fifo->out = 0;
+	fifo->done = 0;
+	fifo->avail = fifo->size;
+	fifo->open = 0;
+	fifo->corrupt = 0;
+}
+
+/**
+ * dma_fifo_in - copies data into the fifo
+ * @fifo: address of in-place "struct dma_fifo" to write to
+ * @src: buffer to copy from
+ * @n: # of bytes to copy
+ *
+ * Returns the # of bytes actually copied, which can be less than requested if
+ * the fifo becomes full. If < 0, return is error code.
+ */
+int dma_fifo_in(struct dma_fifo *fifo, const void *src, int n)
+{
+	int ofs, l;
+
+	if (fifo->data == NULL)
+		return -ENOENT;
+	if (fifo->corrupt)
+		return -ENXIO;
+
+	if (n > fifo->avail)
+		n = fifo->avail;
+	if (n <= 0)
+		return 0;
+
+	ofs = fifo->in % fifo->capacity;
+	l = min(n, fifo->capacity - ofs);
+	memcpy(fifo->data + ofs, src, l);
+	memcpy(fifo->data, src + l, n - l);
+
+	if (FAIL(fifo, addr_check(fifo->done, fifo->in, fifo->in + n) ||
+			fifo->avail < n,
+			"fifo corrupt: in:%u out:%u done:%u n:%d avail:%d",
+			fifo->in, fifo->out, fifo->done, n, fifo->avail))
+		return -ENXIO;
+
+	fifo->in += n;
+	fifo->avail -= n;
+
+	df_trace("in:%u out:%u done:%u n:%d avail:%d", fifo->in, fifo->out,
+		 fifo->done, n, fifo->avail);
+
+	return n;
+}
+
+/**
+ * dma_fifo_out_pend - gets address/len of next avail read and marks as pended
+ * @fifo: address of in-place "struct dma_fifo" to read from
+ * @pended: address of structure to fill with read address/len
+ *          The data/len fields will be NULL/0 if no dma is pended.
+ *
+ * Returns the # of used bytes remaining in fifo (ie, if > 0, more data
+ * remains in the fifo that was not pended). If < 0, return is error code.
+ */
+int dma_fifo_out_pend(struct dma_fifo *fifo, struct dma_pending *pended)
+{
+	unsigned len, n, ofs, l, limit;
+
+	if (fifo->data == NULL)
+		return -ENOENT;
+	if (fifo->corrupt)
+		return -ENXIO;
+
+	pended->len = 0;
+	pended->data = NULL;
+	pended->out = fifo->out;
+
+	len = fifo->in - fifo->out;
+	if (!len)
+		return -ENODATA;
+	if (fifo->open == fifo->open_limit)
+		return -EAGAIN;
+
+	n = len;
+	ofs = fifo->out % fifo->capacity;
+	l = fifo->capacity - ofs;
+	limit = min_t(unsigned, l, fifo->tx_limit);
+	if (n > limit) {
+		n = limit;
+		fifo->out += limit;
+	} else if (ofs + n > fifo->guard) {
+		fifo->out += l;
+		fifo->in = fifo->out;
+	} else {
+		fifo->out += round_up(n, fifo->align);
+		fifo->in = fifo->out;
+	}
+
+	df_trace("in: %u out: %u done: %u n: %d len: %u avail: %d", fifo->in,
+		 fifo->out, fifo->done, n, len, fifo->avail);
+
+	pended->len = n;
+	pended->data = fifo->data + ofs;
+	pended->next = fifo->out;
+	list_add_tail(&pended->link, &fifo->pending);
+	++fifo->open;
+
+	if (FAIL(fifo, fifo->open > fifo->open_limit,
+			"past open limit:%d (limit:%d)",
+			fifo->open, fifo->open_limit))
+		return -ENXIO;
+	if (FAIL(fifo, fifo->out & (fifo->align - 1),
+			"fifo out unaligned:%u (align:%u)",
+			fifo->out, fifo->align))
+		return -ENXIO;
+
+	return len - n;
+}
+
+/**
+ * dma_fifo_out_complete - marks pended dma as completed
+ * @fifo: address of in-place "struct dma_fifo" which was read from
+ * @complete: address of structure for previously pended dma to mark completed
+ */
+int dma_fifo_out_complete(struct dma_fifo *fifo, struct dma_pending *complete)
+{
+	struct dma_pending *pending, *next, *tmp;
+
+	if (fifo->data == NULL)
+		return -ENOENT;
+	if (fifo->corrupt)
+		return -ENXIO;
+	if (list_empty(&fifo->pending) && fifo->open == 0)
+		return -EINVAL;
+
+	if (FAIL(fifo, list_empty(&fifo->pending) != (fifo->open == 0),
+			"pending list disagrees with open count:%d",
+			fifo->open))
+		return -ENXIO;
+
+	tmp = complete->data;
+	*tmp = *complete;
+	list_replace(&complete->link, &tmp->link);
+	dp_mark_completed(tmp);
+
+	/* Only update the fifo in the original pended order */
+	list_for_each_entry_safe(pending, next, &fifo->pending, link) {
+		if (!dp_is_completed(pending)) {
+			df_trace("still pending: saved out: %u len: %d",
+				 pending->out, pending->len);
+			break;
+		}
+
+		if (FAIL(fifo, pending->out != fifo->done ||
+				addr_check(fifo->in, fifo->done, pending->next),
+				"in:%u out:%u done:%u saved:%u next:%u",
+				fifo->in, fifo->out, fifo->done, pending->out,
+				pending->next))
+			return -ENXIO;
+
+		list_del_init(&pending->link);
+		fifo->done = pending->next;
+		fifo->avail += pending->len;
+		--fifo->open;
+
+		df_trace("in: %u out: %u done: %u len: %u avail: %d", fifo->in,
+			 fifo->out, fifo->done, pending->len, fifo->avail);
+	}
+
+	if (FAIL(fifo, fifo->open < 0, "open dma:%d < 0", fifo->open))
+		return -ENXIO;
+	if (FAIL(fifo, fifo->avail > fifo->size, "fifo avail:%d > size:%d",
+			fifo->avail, fifo->size))
+		return -ENXIO;
+
+	return 0;
+}

drivers/staging/fwserial/dma_fifo.h

+/*
+ * DMA-able FIFO interface
+ *
+ * Copyright (C) 2012 Peter Hurley <peter@hurleysoftware.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifndef _DMA_FIFO_H_
+#define _DMA_FIFO_H_
+
+/**
+ * The design basis for the DMA FIFO is to provide an output side that
+ * complies with the streaming DMA API design that can be DMA'd from directly
+ * (without additional copying), coupled with an input side that maintains a
+ * logically consistent 'apparent' size (ie, bytes in + bytes avail is static
+ * for the lifetime of the FIFO).
+ *
+ * DMA output transactions originate on a cache line boundary and can be
+ * variably-sized. DMA output transactions can be retired out-of-order but
+ * the FIFO will only advance the output in the original input sequence.
+ * This means the FIFO will eventually stall if a transaction is never retired.
+ *
+ * Chunking the output side into cache line multiples means that some FIFO
+ * memory is unused. For example, if all the avail input has been pended out,
+ * then the in and out markers are re-aligned to the next cache line.
+ * The maximum possible waste is
+ *     (cache line alignment - 1) * (max outstanding dma transactions)
+ * This potential waste requires additional hidden capacity within the FIFO
+ * to be able to accept input while the 'apparent' size has not been reached.
+ *
+ * Additional cache lines (ie, guard area) are used to minimize DMA
+ * fragmentation when wrapping at the end of the FIFO. Input is allowed into the
+ * guard area, but the in and out FIFO markers are wrapped when DMA is pended.
+ */
+
+#define DMA_FIFO_GUARD 3   /* # of cache lines to reserve for the guard area */
+
+struct dma_fifo {
+	unsigned	 in;
+	unsigned	 out;		/* updated when dma is pended         */
+	unsigned	 done;		/* updated upon dma completion        */
+	struct {
+		unsigned corrupt:1;
+	};
+	int		 size;		/* 'apparent' size of fifo	      */
+	int		 guard;		/* ofs of guard area		      */
+	int		 capacity;	/* size + reserved                    */
+	int		 avail;		/* # of unused bytes in fifo          */
+	unsigned	 align;		/* must be power of 2                 */
+	int		 tx_limit;	/* max # of bytes per dma transaction */
+	int		 open_limit;	/* max # of outstanding allowed       */
+	int		 open;		/* # of outstanding dma transactions  */
+	struct list_head pending;	/* fifo markers for outstanding dma   */
+	void		 *data;
+};
+
+struct dma_pending {
+	struct list_head link;
+	void		 *data;
+	unsigned	 len;
+	unsigned         next;
+	unsigned         out;
+};
+
+static inline void dp_mark_completed(struct dma_pending *dp)
+{
+	dp->data += 1;
+}
+
+static inline bool dp_is_completed(struct dma_pending *dp)
+{
+	return (unsigned long)dp->data & 1UL;
+}
+
+extern void dma_fifo_init(struct dma_fifo *fifo);
+extern int dma_fifo_alloc(struct dma_fifo *fifo, int size, unsigned align,
+			  int tx_limit, int open_limit, gfp_t gfp_mask);
+extern void dma_fifo_free(struct dma_fifo *fifo);
+extern void dma_fifo_reset(struct dma_fifo *fifo);
+extern int dma_fifo_in(struct dma_fifo *fifo, const void *src, int n);
+extern int dma_fifo_out_pend(struct dma_fifo *fifo, struct dma_pending *pended);
+extern int dma_fifo_out_complete(struct dma_fifo *fifo,
+				 struct dma_pending *complete);
+
+/* returns the # of used bytes in the fifo */
+static inline int dma_fifo_level(struct dma_fifo *fifo)
+{
+	return fifo->size - fifo->avail;
+}
+
+/* returns the # of bytes ready for output in the fifo */
+static inline int dma_fifo_out_level(struct dma_fifo *fifo)
+{
+	return fifo->in - fifo->out;
+}
+
+/* returns the # of unused bytes in the fifo */
+static inline int dma_fifo_avail(struct dma_fifo *fifo)
+{
+	return fifo->avail;
+}
+
+/* returns true if fifo has max # of outstanding dmas */
+static inline bool dma_fifo_busy(struct dma_fifo *fifo)
+{
+	return fifo->open == fifo->open_limit;
+}
+
+/* changes the max size of dma returned from dma_fifo_out_pend() */
+static inline int dma_fifo_change_tx_limit(struct dma_fifo *fifo, int tx_limit)
+{
+	tx_limit = round_down(tx_limit, fifo->align);
+	fifo->tx_limit = max_t(int, tx_limit, fifo->align);
+	return 0;
+}
+
+#endif /* _DMA_FIFO_H_ */