V4L/DVB (9361): Dynamic DVB minor allocation

Implement dynamic minor allocation for DVB, to allow more than four
devices of the same type per adapter, based on drivers/usb/core/file.c.

Add a new config option, DVB_DYNAMIC_MINORS, to make use of this
feature, which defaults to no for backwards compatibility.

Signed-off-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 52 insertions, 19 deletions

diff --git a/drivers/media/dvb/Kconfig b/drivers/media/dvb/Kconfig
index 0bcd852576d6..40ebde53b3ce 100644
--- a/drivers/media/dvb/Kconfig
+++ b/drivers/media/dvb/Kconfig
@@ -2,6 +2,19 @@
 # DVB device configuration
 #
 
+config DVB_DYNAMIC_MINORS
+        bool "Dynamic DVB minor allocation"
+        depends on DVB_CORE
+        default n
+        help
+          If you say Y here, the DVB subsystem will use dynamic minor
+          allocation for any device that uses the DVB major number.
+          This means that you can have more than 4 of a single type
+          of device (like demuxes and frontends) per adapter, but udev
+          will be required to manage the device nodes.
+
+          If you are unsure about this, say N here.
+
 menuconfig DVB_CAPTURE_DRIVERS
         bool "DVB/ATSC adapters"
         depends on DVB_CORE
diff --git a/drivers/media/dvb/dvb-core/dvbdev.c b/drivers/media/dvb/dvb-core/dvbdev.c
index a113744a56cc..e363a3b5054c 100644
--- a/drivers/media/dvb/dvb-core/dvbdev.c
+++ b/drivers/media/dvb/dvb-core/dvbdev.c
@@ -50,33 +50,27 @@ static const char * const dnames[] = {
         "net", "osd"
 };
 
+#ifdef CONFIG_DVB_DYNAMIC_MINORS
+#define MAX_DVB_MINORS          256
+#define DVB_MAX_IDS             MAX_DVB_MINORS
+#else
 #define DVB_MAX_IDS             4
 #define nums2minor(num,type,id) ((num << 6) | (id << 4) | type)
 #define MAX_DVB_MINORS          (DVB_MAX_ADAPTERS*64)
+#endif
 
 static struct class *dvb_class;
 
-static struct dvb_device* dvbdev_find_device (int minor)
-{
-        struct dvb_adapter *adap;
-
-        list_for_each_entry(adap, &dvb_adapter_list, list_head) {
-                struct dvb_device *dev;
-                list_for_each_entry(dev, &adap->device_list, list_head)
-                        if (nums2minor(adap->num, dev->type, dev->id) == minor)
-                                return dev;
-        }
-
-        return NULL;
-}
-
+static struct dvb_device *dvb_minors[MAX_DVB_MINORS];
+static DECLARE_RWSEM(minor_rwsem);
 
 static int dvb_device_open(struct inode *inode, struct file *file)
 {
         struct dvb_device *dvbdev;
 
         lock_kernel();
-        dvbdev = dvbdev_find_device (iminor(inode));
+        down_read(&minor_rwsem);
+        dvbdev = dvb_minors[iminor(inode)];
 
         if (dvbdev && dvbdev->fops) {
                 int err = 0;
@@ -92,9 +86,11 @@ static int dvb_device_open(struct inode *inode, struct file *file)
                         file->f_op = fops_get(old_fops);
                 }
                 fops_put(old_fops);
+                up_read(&minor_rwsem);
                 unlock_kernel();
                 return err;
         }
+        up_read(&minor_rwsem);
         unlock_kernel();
         return -ENODEV;
 }
@@ -192,6 +188,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
         struct dvb_device *dvbdev;
         struct file_operations *dvbdevfops;
         struct device *clsdev;
+        int minor;
         int id;
 
         mutex_lock(&dvbdev_register_lock);
@@ -231,6 +228,26 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 
         list_add_tail (&dvbdev->list_head, &adap->device_list);
 
+        down_write(&minor_rwsem);
+#ifdef CONFIG_DVB_DYNAMIC_MINORS
+        for (minor = 0; minor < MAX_DVB_MINORS; minor++)
+                if (dvb_minors[minor] == NULL)
+                        break;
+
+        if (minor == MAX_DVB_MINORS) {
+                kfree(dvbdevfops);
+                kfree(dvbdev);
+                mutex_unlock(&dvbdev_register_lock);
+                return -EINVAL;
+        }
+#else
+        minor = nums2minor(adap->num, type, id);
+#endif
+
+        dvbdev->minor = minor;
+        dvb_minors[minor] = dvbdev;
+        up_write(&minor_rwsem);
+
         mutex_unlock(&dvbdev_register_lock);
 
         clsdev = device_create(dvb_class, adap->device,
@@ -243,8 +260,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
         }
 
         dprintk(KERN_DEBUG "DVB: register adapter%d/%s%d @ minor: %i (0x%02x)\n",
-                adap->num, dnames[type], id, nums2minor(adap->num, type, id),
-                nums2minor(adap->num, type, id));
+                adap->num, dnames[type], id, minor, minor);
 
         return 0;
 }
@@ -256,8 +272,11 @@ void dvb_unregister_device(struct dvb_device *dvbdev)
         if (!dvbdev)
                 return;
 
-        device_destroy(dvb_class, MKDEV(DVB_MAJOR, nums2minor(dvbdev->adapter->num,
-                       dvbdev->type, dvbdev->id)));
+        down_write(&minor_rwsem);
+        dvb_minors[dvbdev->minor] = NULL;
+        up_write(&minor_rwsem);
+
+        device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
 
         list_del (&dvbdev->list_head);
         kfree (dvbdev->fops);
diff --git a/drivers/media/dvb/dvb-core/dvbdev.h b/drivers/media/dvb/dvb-core/dvbdev.h
index 574e336bac35..dca49cf962e8 100644
--- a/drivers/media/dvb/dvb-core/dvbdev.h
+++ b/drivers/media/dvb/dvb-core/dvbdev.h
@@ -74,6 +74,7 @@ struct dvb_device {
         struct file_operations *fops;
         struct dvb_adapter *adapter;
         int type;
+        int minor;
         u32 id;
 
         /* in theory, 'users' can vanish now,