V4L/DVB (5862): V4L: Add internal ioctl-like interface.

This patch adds an internal ioctl-like interface which can be used in
situations where a single Video4Linux device is implemented by multiple
device drivers. One master device controls one or more slave devices.
The slaves provide Video4Linux ioctl-like interface for the use of the
master.

Only a handful of ioctls are implemented at the moment. More can (and
should) be added as more functionality is required.

Signed-off-by: Sakari Ailus <sakari.ailus@nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

2 files changed, 156 insertions, 1 deletions

diff --git a/drivers/media/video/Makefile b/drivers/media/video/Makefile
index 10b4d4469016..d35306daac2f 100644
--- a/drivers/media/video/Makefile
+++ b/drivers/media/video/Makefile
@@ -11,7 +11,8 @@ tuner-$(CONFIG_TUNER_TEA5761)	+= tea5761.o
 
 msp3400-objs    :=      msp3400-driver.o msp3400-kthreads.o
 
-obj-$(CONFIG_VIDEO_DEV) += videodev.o v4l2-common.o compat_ioctl32.o
+obj-$(CONFIG_VIDEO_DEV) += videodev.o v4l2-common.o compat_ioctl32.o \
+                           v4l2-int-device.o
 
 ifeq ($(CONFIG_VIDEO_V4L1_COMPAT),y)
   obj-$(CONFIG_VIDEO_DEV) += v4l1-compat.o
diff --git a/drivers/media/video/v4l2-int-device.c b/drivers/media/video/v4l2-int-device.c
new file mode 100644
index 000000000000..7885d9b38c92
--- /dev/null
+++ b/drivers/media/video/v4l2-int-device.c
@@ -0,0 +1,154 @@
+/*
+ * drivers/media/video/v4l2-int-device.c
+ *
+ * V4L2 internal ioctl interface.
+ *
+ * Copyright (C) 2007 Nokia Corporation.
+ *
+ * Contact: Sakari Ailus <sakari.ailus@nokia.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * 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., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/sort.h>
+#include <linux/string.h>
+
+#include <media/v4l2-int-device.h>
+
+static DEFINE_MUTEX(mutex);
+static LIST_HEAD(int_list);
+
+static void v4l2_int_device_try_attach_all(void)
+{
+        struct list_head *head_master;
+
+        list_for_each(head_master, &int_list) {
+                struct list_head *head_slave;
+                struct v4l2_int_device *m =
+                        list_entry(head_master, struct v4l2_int_device, head);
+
+                if (m->type != v4l2_int_type_master)
+                        continue;
+
+                list_for_each(head_slave, &int_list) {
+                        struct v4l2_int_device *s =
+                                list_entry(head_slave,
+                                           struct v4l2_int_device, head);
+
+                        if (s->type != v4l2_int_type_slave)
+                                continue;
+
+                        /* Slave is connected? */
+                        if (s->u.slave->master)
+                                continue;
+
+                        /* Slave wants to attach to master? */
+                        if (s->u.slave->attach_to[0] != 0
+                            && strncmp(m->name, s->u.slave->attach_to,
+                                       V4L2NAMESIZE))
+                                continue;
+
+                        if (!try_module_get(m->module))
+                                continue;
+
+                        if (m->u.master->attach(m, s)) {
+                                module_put(m->module);
+                                continue;
+                        }
+
+                        s->u.slave->master = m;
+                }
+        }
+}
+
+static int ioctl_sort_cmp(const void *a, const void *b)
+{
+        const struct v4l2_int_ioctl_desc *d1 = a, *d2 = b;
+
+        if (d1->num > d2->num)
+                return 1;
+
+        if (d1->num < d2->num)
+                return -1;
+
+        return 0;
+}
+
+int v4l2_int_device_register(struct v4l2_int_device *d)
+{
+        if (d->type == v4l2_int_type_slave)
+                sort(d->u.slave->ioctls, d->u.slave->num_ioctls,
+                     sizeof(struct v4l2_int_ioctl_desc),
+                     &ioctl_sort_cmp, NULL);
+        mutex_lock(&mutex);
+        list_add(&d->head, &int_list);
+        v4l2_int_device_try_attach_all();
+        mutex_unlock(&mutex);
+
+        return 0;
+}
+
+void v4l2_int_device_unregister(struct v4l2_int_device *d)
+{
+        mutex_lock(&mutex);
+        list_del(&d->head);
+        if (d->type == v4l2_int_type_slave
+            && d->u.slave->master != NULL) {
+                d->u.slave->master->u.master->detach(d);
+                module_put(d->u.slave->master->module);
+                d->u.slave->master = NULL;
+        }
+        mutex_unlock(&mutex);
+}
+
+static int no_such_ioctl(struct v4l2_int_device *d)
+{
+        return -EINVAL;
+}
+
+/* Adapted from search_extable in extable.c. */
+static v4l2_int_ioctl_func *find_ioctl(struct v4l2_int_slave *slave, int cmd)
+{
+        const struct v4l2_int_ioctl_desc *first = slave->ioctls;
+        const struct v4l2_int_ioctl_desc *last =
+                first + slave->num_ioctls - 1;
+
+        while (first <= last) {
+                const struct v4l2_int_ioctl_desc *mid;
+
+                mid = (last - first) / 2 + first;
+
+                if (mid->num < cmd)
+                        first = mid + 1;
+                else if (mid->num > cmd)
+                        last = mid - 1;
+                else
+                        return mid->func;
+        }
+
+        return &no_such_ioctl;
+}
+
+int v4l2_int_ioctl_0(struct v4l2_int_device *d, int cmd)
+{
+        return ((v4l2_int_ioctl_func_0 *)find_ioctl(d->u.slave, cmd))(d);
+}
+
+int v4l2_int_ioctl_1(struct v4l2_int_device *d, int cmd, void *arg)
+{
+        return ((v4l2_int_ioctl_func_1 *)find_ioctl(d->u.slave, cmd))(d, arg);
+}