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Subject[PATCH v5 3/8] drivers/fsi: sbefifo: Add miscdevice
Date
From: "Edward A. James" <eajames@us.ibm.com>

Add a miscdevice for the sbefifo to allow userspace access through
standard file operations.

Signed-off-by: Edward A. James <eajames@us.ibm.com>
---
drivers/fsi/fsi-sbefifo.c | 355 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 355 insertions(+)

diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index 6ba190a..fed3739 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -19,6 +19,7 @@
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/list.h>
+#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h>
@@ -54,6 +55,7 @@
struct sbefifo {
struct timer_list poll_timer;
struct fsi_device *fsi_dev;
+ struct miscdevice mdev;
wait_queue_head_t wait;
struct list_head xfrs;
struct kref kref;
@@ -256,6 +258,99 @@ static void sbefifo_put(struct sbefifo *sbefifo)
kref_put(&sbefifo->kref, sbefifo_free);
}

+static struct sbefifo_xfr *sbefifo_enq_xfr(struct sbefifo_client *client)
+{
+ struct sbefifo *sbefifo = client->dev;
+ struct sbefifo_xfr *xfr;
+
+ if (READ_ONCE(sbefifo->rc))
+ return ERR_PTR(sbefifo->rc);
+
+ xfr = kzalloc(sizeof(*xfr), GFP_KERNEL);
+ if (!xfr)
+ return ERR_PTR(-ENOMEM);
+
+ xfr->rbuf = &client->rbuf;
+ xfr->wbuf = &client->wbuf;
+ list_add_tail(&xfr->xfrs, &sbefifo->xfrs);
+ list_add_tail(&xfr->client, &client->xfrs);
+
+ return xfr;
+}
+
+static bool sbefifo_xfr_rsp_pending(struct sbefifo_client *client)
+{
+ struct sbefifo_xfr *xfr = list_first_entry_or_null(&client->xfrs,
+ struct sbefifo_xfr,
+ client);
+
+ if (xfr && test_bit(SBEFIFO_XFR_RESP_PENDING, &xfr->flags))
+ return true;
+
+ return false;
+}
+
+static struct sbefifo_client *sbefifo_new_client(struct sbefifo *sbefifo)
+{
+ struct sbefifo_client *client;
+
+ client = kzalloc(sizeof(*client), GFP_KERNEL);
+ if (!client)
+ return NULL;
+
+ kref_init(&client->kref);
+ client->dev = sbefifo;
+ sbefifo_buf_init(&client->rbuf);
+ sbefifo_buf_init(&client->wbuf);
+ INIT_LIST_HEAD(&client->xfrs);
+
+ sbefifo_get(sbefifo);
+
+ return client;
+}
+
+static void sbefifo_client_release(struct kref *kref)
+{
+ struct sbefifo *sbefifo;
+ struct sbefifo_client *client;
+ struct sbefifo_xfr *xfr, *tmp;
+
+ client = container_of(kref, struct sbefifo_client, kref);
+ sbefifo = client->dev;
+
+ if (!READ_ONCE(sbefifo->rc)) {
+ list_for_each_entry_safe(xfr, tmp, &client->xfrs, client) {
+ if (test_bit(SBEFIFO_XFR_COMPLETE, &xfr->flags)) {
+ list_del(&xfr->client);
+ kfree(xfr);
+ continue;
+ }
+
+ /*
+ * The client left with pending or running xfrs.
+ * Cancel them.
+ */
+ set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
+ sbefifo_get(sbefifo);
+ if (mod_timer(&client->dev->poll_timer, jiffies))
+ sbefifo_put(sbefifo);
+ }
+ }
+
+ sbefifo_put(sbefifo);
+ kfree(client);
+}
+
+static void sbefifo_get_client(struct sbefifo_client *client)
+{
+ kref_get(&client->kref);
+}
+
+static void sbefifo_put_client(struct sbefifo_client *client)
+{
+ kref_put(&client->kref, sbefifo_client_release);
+}
+
static struct sbefifo_xfr *sbefifo_next_xfr(struct sbefifo *sbefifo)
{
struct sbefifo_xfr *xfr, *tmp;
@@ -430,6 +525,252 @@ static void sbefifo_poll_timer(unsigned long data)
spin_unlock_irqrestore(&sbefifo->lock, flags);
}

+static int sbefifo_open(struct inode *inode, struct file *file)
+{
+ struct sbefifo *sbefifo = container_of(file->private_data,
+ struct sbefifo, mdev);
+ struct sbefifo_client *client;
+ int ret;
+
+ ret = READ_ONCE(sbefifo->rc);
+ if (ret)
+ return ret;
+
+ client = sbefifo_new_client(sbefifo);
+ if (!client)
+ return -ENOMEM;
+
+ file->private_data = client;
+
+ return 0;
+}
+
+static unsigned int sbefifo_poll(struct file *file, poll_table *wait)
+{
+ struct sbefifo_client *client = file->private_data;
+ struct sbefifo *sbefifo = client->dev;
+ unsigned int mask = 0;
+
+ poll_wait(file, &sbefifo->wait, wait);
+
+ if (READ_ONCE(sbefifo->rc))
+ mask |= POLLERR;
+
+ if (sbefifo_buf_nbreadable(&client->rbuf))
+ mask |= POLLIN;
+
+ if (sbefifo_buf_nbwriteable(&client->wbuf))
+ mask |= POLLOUT;
+
+ return mask;
+}
+
+static bool sbefifo_read_ready(struct sbefifo *sbefifo,
+ struct sbefifo_client *client, size_t *n,
+ size_t *ret)
+{
+ struct sbefifo_xfr *xfr = list_first_entry_or_null(&client->xfrs,
+ struct sbefifo_xfr,
+ client);
+
+ *n = sbefifo_buf_nbreadable(&client->rbuf);
+ *ret = READ_ONCE(sbefifo->rc);
+
+ return *ret || *n ||
+ (xfr && test_bit(SBEFIFO_XFR_COMPLETE, &xfr->flags));
+}
+
+static ssize_t sbefifo_read(struct file *file, char __user *buf, size_t len,
+ loff_t *offset)
+{
+ struct sbefifo_client *client = file->private_data;
+ struct sbefifo *sbefifo = client->dev;
+ struct sbefifo_xfr *xfr;
+ size_t n;
+ ssize_t ret = 0;
+
+ if ((len >> 2) << 2 != len)
+ return -EINVAL;
+
+ if ((file->f_flags & O_NONBLOCK) && !sbefifo_xfr_rsp_pending(client))
+ return -EAGAIN;
+
+ sbefifo_get_client(client);
+ if (wait_event_interruptible(sbefifo->wait,
+ sbefifo_read_ready(sbefifo, client, &n,
+ &ret))) {
+ ret = -ERESTARTSYS;
+ goto out;
+ }
+
+ if (ret) {
+ INIT_LIST_HEAD(&client->xfrs);
+ goto out;
+ }
+
+ n = min_t(size_t, n, len);
+
+ if (copy_to_user(buf, READ_ONCE(client->rbuf.rpos), n)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ if (sbefifo_buf_readnb(&client->rbuf, n)) {
+ xfr = list_first_entry_or_null(&client->xfrs,
+ struct sbefifo_xfr, client);
+ if (!xfr) {
+ /* should be impossible to not have an xfr here */
+ WARN_ONCE(1, "no xfr in queue");
+ ret = -EPROTO;
+ goto out;
+ }
+
+ if (!test_bit(SBEFIFO_XFR_COMPLETE, &xfr->flags)) {
+ /* Fill the read buffer back up. */
+ sbefifo_get(sbefifo);
+ if (mod_timer(&client->dev->poll_timer, jiffies))
+ sbefifo_put(sbefifo);
+ } else {
+ list_del(&xfr->client);
+ kfree(xfr);
+ wake_up_interruptible(&sbefifo->wait);
+ }
+ }
+
+ ret = n;
+
+out:
+ sbefifo_put_client(client);
+ return ret;
+}
+
+static bool sbefifo_write_ready(struct sbefifo *sbefifo,
+ struct sbefifo_xfr *xfr,
+ struct sbefifo_client *client, size_t *n)
+{
+ struct sbefifo_xfr *next = list_first_entry_or_null(&client->xfrs,
+ struct sbefifo_xfr,
+ client);
+
+ *n = sbefifo_buf_nbwriteable(&client->wbuf);
+ return READ_ONCE(sbefifo->rc) || (next == xfr && *n);
+}
+
+static ssize_t sbefifo_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *offset)
+{
+ unsigned long flags;
+ struct sbefifo_client *client = file->private_data;
+ struct sbefifo *sbefifo = client->dev;
+ struct sbefifo_xfr *xfr;
+ ssize_t ret = 0;
+ size_t n;
+
+ if ((len >> 2) << 2 != len)
+ return -EINVAL;
+
+ if (!len)
+ return 0;
+
+ sbefifo_get_client(client);
+ n = sbefifo_buf_nbwriteable(&client->wbuf);
+
+ spin_lock_irqsave(&sbefifo->lock, flags);
+ xfr = sbefifo_next_xfr(sbefifo); /* next xfr to be executed */
+
+ if ((file->f_flags & O_NONBLOCK) && xfr && n < len) {
+ spin_unlock_irqrestore(&sbefifo->lock, flags);
+ ret = -EAGAIN;
+ goto out;
+ }
+
+ xfr = sbefifo_enq_xfr(client); /* this xfr queued up */
+ if (IS_ERR(xfr)) {
+ spin_unlock_irqrestore(&sbefifo->lock, flags);
+ ret = PTR_ERR(xfr);
+ goto out;
+ }
+
+ spin_unlock_irqrestore(&sbefifo->lock, flags);
+
+ /*
+ * Partial writes are not really allowed in that EOT is sent exactly
+ * once per write.
+ */
+ while (len) {
+ if (wait_event_interruptible(sbefifo->wait,
+ sbefifo_write_ready(sbefifo, xfr,
+ client,
+ &n))) {
+ set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
+ sbefifo_get(sbefifo);
+ if (mod_timer(&sbefifo->poll_timer, jiffies))
+ sbefifo_put(sbefifo);
+
+ ret = -ERESTARTSYS;
+ goto out;
+ }
+
+ if (sbefifo->rc) {
+ INIT_LIST_HEAD(&client->xfrs);
+ ret = sbefifo->rc;
+ goto out;
+ }
+
+ n = min_t(size_t, n, len);
+
+ if (copy_from_user(READ_ONCE(client->wbuf.wpos), buf, n)) {
+ set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
+ sbefifo_get(sbefifo);
+ if (mod_timer(&sbefifo->poll_timer, jiffies))
+ sbefifo_put(sbefifo);
+ ret = -EFAULT;
+ goto out;
+ }
+
+ buf += n;
+
+ sbefifo_buf_wrotenb(&client->wbuf, n);
+ len -= n;
+ ret += n;
+
+ /*
+ * Set this before starting timer to avoid race condition on
+ * this flag with the timer function writer.
+ */
+ if (!len)
+ set_bit(SBEFIFO_XFR_WRITE_DONE, &xfr->flags);
+
+ /* Drain the write buffer. */
+ sbefifo_get(sbefifo);
+ if (mod_timer(&client->dev->poll_timer, jiffies))
+ sbefifo_put(sbefifo);
+ }
+
+out:
+ sbefifo_put_client(client);
+ return ret;
+}
+
+static int sbefifo_release(struct inode *inode, struct file *file)
+{
+ struct sbefifo_client *client = file->private_data;
+ struct sbefifo *sbefifo = client->dev;
+
+ sbefifo_put_client(client);
+
+ return READ_ONCE(sbefifo->rc);
+}
+
+static const struct file_operations sbefifo_fops = {
+ .owner = THIS_MODULE,
+ .open = sbefifo_open,
+ .read = sbefifo_read,
+ .write = sbefifo_write,
+ .poll = sbefifo_poll,
+ .release = sbefifo_release,
+};
+
static int sbefifo_request_reset(struct sbefifo *sbefifo)
{
int ret;
@@ -504,6 +845,18 @@ static int sbefifo_probe(struct device *dev)
setup_timer(&sbefifo->poll_timer, sbefifo_poll_timer,
(unsigned long)sbefifo);

+ sbefifo->mdev.minor = MISC_DYNAMIC_MINOR;
+ sbefifo->mdev.fops = &sbefifo_fops;
+ sbefifo->mdev.name = sbefifo->name;
+ sbefifo->mdev.parent = dev;
+ ret = misc_register(&sbefifo->mdev);
+ if (ret) {
+ dev_err(dev, "failed to register miscdevice: %d\n", ret);
+ ida_simple_remove(&sbefifo_ida, sbefifo->idx);
+ sbefifo_put(sbefifo);
+ return ret;
+ }
+
dev_set_drvdata(dev, sbefifo);

return 0;
@@ -529,6 +882,8 @@ static int sbefifo_remove(struct device *dev)

wake_up_all(&sbefifo->wait);

+ misc_deregister(&sbefifo->mdev);
+
ida_simple_remove(&sbefifo_ida, sbefifo->idx);

if (del_timer_sync(&sbefifo->poll_timer))
--
1.8.3.1
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