2.1. Digital TV Common functions¶
2.1.1. Math functions¶
Provide some commonly-used math functions, usually required in order to estimate signal strength and signal to noise measurements in dB.
-
unsigned int
intlog2
(u32 value)¶ computes log2 of a value; the result is shifted left by 24 bits
Parameters
u32 value
- The value (must be != 0)
Description
to use rational values you can use the following method:
intlog2(value) = intlog2(value * 2^x) - x * 2^24
Some usecase examples:
intlog2(8) will give 3 << 24 = 3 * 2^24
intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
Return
log2(value) * 2^24
-
unsigned int
intlog10
(u32 value)¶ computes log10 of a value; the result is shifted left by 24 bits
Parameters
u32 value
- The value (must be != 0)
Description
to use rational values you can use the following method:
intlog10(value) = intlog10(value * 10^x) - x * 2^24
An usecase example:
intlog10(1000) will give 3 << 24 = 3 * 2^24due to the implementation intlog10(1000) might be not exactly 3 * 2^24
look at intlog2 for similar examples
Return
log10(value) * 2^24
2.1.2. DVB devices¶
Those functions are responsible for handling the DVB device nodes.
-
enum
dvb_device_type
¶ type of the Digital TV device
Constants
DVB_DEVICE_SEC
- Digital TV standalone Common Interface (CI)
DVB_DEVICE_FRONTEND
- Digital TV frontend.
DVB_DEVICE_DEMUX
- Digital TV demux.
DVB_DEVICE_DVR
- Digital TV digital video record (DVR).
DVB_DEVICE_CA
- Digital TV Conditional Access (CA).
DVB_DEVICE_NET
- Digital TV network.
DVB_DEVICE_VIDEO
- Digital TV video decoder. Deprecated. Used only on av7110-av.
DVB_DEVICE_AUDIO
- Digital TV audio decoder. Deprecated. Used only on av7110-av.
DVB_DEVICE_OSD
- Digital TV On Screen Display (OSD). Deprecated. Used only on av7110.
-
struct
dvb_adapter
¶ represents a Digital TV adapter using Linux DVB API
Definition
struct dvb_adapter {
int num;
struct list_head list_head;
struct list_head device_list;
const char * name;
u8 proposed_mac;
void * priv;
struct device * device;
struct module * module;
int mfe_shared;
struct dvb_device * mfe_dvbdev;
struct mutex mfe_lock;
#if defined(CONFIG_MEDIA_CONTROLLER_DVB
struct media_device * mdev;
struct media_entity * conn;
struct media_pad * conn_pads;
#endif
};
Members
num
- Number of the adapter
list_head
- List with the DVB adapters
device_list
- List with the DVB devices
name
- Name of the adapter
proposed_mac
- proposed MAC address for the adapter
priv
- private data
device
- pointer to struct device
module
- pointer to struct module
mfe_shared
- mfe shared: indicates mutually exclusive frontends Thie usage of this flag is currently deprecated
mfe_dvbdev
- Frontend device in use, in the case of MFE
mfe_lock
- Lock to prevent using the other frontends when MFE is used.
mdev
- pointer to struct media_device, used when the media controller is used.
conn
- RF connector. Used only if the device has no separate tuner.
conn_pads
- pointer to struct media_pad associated with conn;
-
struct
dvb_device
¶ represents a DVB device node
Definition
struct dvb_device {
struct list_head list_head;
const struct file_operations * fops;
struct dvb_adapter * adapter;
enum dvb_device_type type;
int minor;
u32 id;
int readers;
int writers;
int users;
wait_queue_head_t wait_queue;
int (* kernel_ioctl) (struct file *file, unsigned int cmd, void *arg);
#if defined(CONFIG_MEDIA_CONTROLLER_DVB
const char * name;
struct media_intf_devnode * intf_devnode;
unsigned tsout_num_entities;
struct media_entity * entity;
struct media_entity * tsout_entity;
struct media_pad * pads;
struct media_pad * tsout_pads;
#endif
void * priv;
};
Members
list_head
- List head with all DVB devices
fops
- pointer to struct file_operations
adapter
- pointer to the adapter that holds this device node
type
- type of the device, as defined by
enum dvb_device_type
. minor
- devnode minor number. Major number is always DVB_MAJOR.
id
- device ID number, inside the adapter
readers
- Initialized by the caller. Each call to
open()
in Read Only mode decreases this counter by one. writers
- Initialized by the caller. Each call to
open()
in Read/Write mode decreases this counter by one. users
- Initialized by the caller. Each call to
open()
in any mode decreases this counter by one. wait_queue
- wait queue, used to wait for certain events inside one of the DVB API callers
kernel_ioctl
- callback function used to handle ioctl calls from userspace.
name
- Name to be used for the device at the Media Controller
intf_devnode
- Pointer to media_intf_devnode. Used by the dvbdev core to store the MC device node interface
tsout_num_entities
- Number of Transport Stream output entities
entity
- pointer to struct media_entity associated with the device node
tsout_entity
- array with MC entities associated to each TS output node
pads
- pointer to struct media_pad associated with entity;
tsout_pads
- array with the source pads for each tsout_entity
priv
- private data
Description
This structure is used by the DVB core (frontend, CA, net, demux) in order to create the device nodes. Usually, driver should not initialize this struct diretly.
-
int
dvb_register_adapter
(struct dvb_adapter * adap, const char * name, struct module * module, struct device * device, short * adapter_nums)¶ Registers a new DVB adapter
Parameters
struct dvb_adapter * adap
- pointer to struct dvb_adapter
const char * name
- Adapter’s name
struct module * module
- initialized with THIS_MODULE at the caller
struct device * device
- pointer to struct device that corresponds to the device driver
short * adapter_nums
- Array with a list of the numbers for dvb_register_adapter; to select among them. Typically, initialized with: DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nums)
-
int
dvb_unregister_adapter
(struct dvb_adapter * adap)¶ Unregisters a DVB adapter
Parameters
struct dvb_adapter * adap
- pointer to struct dvb_adapter
-
int
dvb_register_device
(struct dvb_adapter * adap, struct dvb_device ** pdvbdev, const struct dvb_device * template, void * priv, enum dvb_device_type type, int demux_sink_pads)¶ Registers a new DVB device
Parameters
struct dvb_adapter * adap
- pointer to struct dvb_adapter
struct dvb_device ** pdvbdev
- pointer to the place where the new struct dvb_device will be stored
const struct dvb_device * template
- Template used to create
pdvbdev
; void * priv
- private data
enum dvb_device_type type
- type of the device, as defined by
enum dvb_device_type
. int demux_sink_pads
- Number of demux outputs, to be used to create the TS outputs via the Media Controller.
-
void
dvb_remove_device
(struct dvb_device * dvbdev)¶ Remove a registered DVB device
Parameters
struct dvb_device * dvbdev
- pointer to struct dvb_device
Description
This does not free memory. To do that, call dvb_free_device()
.
-
void
dvb_free_device
(struct dvb_device * dvbdev)¶ Free memory occupied by a DVB device.
Parameters
struct dvb_device * dvbdev
- pointer to struct dvb_device
Description
Call dvb_unregister_device()
before calling this function.
-
void
dvb_unregister_device
(struct dvb_device * dvbdev)¶ Unregisters a DVB device
Parameters
struct dvb_device * dvbdev
- pointer to struct dvb_device
Description
This is a combination of dvb_remove_device()
and dvb_free_device()
.
Using this function is usually a mistake, and is often an indicator
for a use-after-free bug (when a userspace process keeps a file
handle to a detached device).
-
int
dvb_create_media_graph
(struct dvb_adapter * adap, bool create_rf_connector)¶ Creates media graph for the Digital TV part of the device.
Parameters
struct dvb_adapter * adap
- pointer to
struct dvb_adapter
bool create_rf_connector
- if true, it creates the RF connector too
Description
This function checks all DVB-related functions at the media controller entities and creates the needed links for the media graph. It is capable of working with multiple tuners or multiple frontends, but it won’t create links if the device has multiple tuners and multiple frontends or if the device has multiple muxes. In such case, the caller driver should manually create the remaining links.
-
void
dvb_register_media_controller
(struct dvb_adapter * adap, struct media_device * mdev)¶ registers a media controller at DVB adapter
Parameters
struct dvb_adapter * adap
- pointer to
struct dvb_adapter
struct media_device * mdev
- pointer to
struct media_device
-
struct media_device *
dvb_get_media_controller
(struct dvb_adapter * adap)¶ gets the associated media controller
Parameters
struct dvb_adapter * adap
- pointer to
struct dvb_adapter
-
int
dvb_generic_open
(struct inode * inode, struct file * file)¶ Digital TV open function, used by DVB devices
Parameters
struct inode * inode
- pointer to
struct inode
. struct file * file
- pointer to
struct file
.
Description
Checks if a DVB devnode is still valid, and if the permissions are OK and increment negative use count.
-
int
dvb_generic_release
(struct inode * inode, struct file * file)¶ Digital TV close function, used by DVB devices
Parameters
struct inode * inode
- pointer to
struct inode
. struct file * file
- pointer to
struct file
.
Description
Checks if a DVB devnode is still valid, and if the permissions are OK and decrement negative use count.
-
long
dvb_generic_ioctl
(struct file * file, unsigned int cmd, unsigned long arg)¶ Digital TV close function, used by DVB devices
Parameters
struct file * file
- pointer to
struct file
. unsigned int cmd
- Ioctl name.
unsigned long arg
- Ioctl argument.
Description
Checks if a DVB devnode and struct dvbdev.kernel_ioctl is still valid.
If so, calls dvb_usercopy()
.
-
int
dvb_usercopy
(struct file * file, unsigned int cmd, unsigned long arg, int (*func) (struct file *file, unsigned int cmd, void *arg)¶ copies data from/to userspace memory when an ioctl is issued.
Parameters
struct file * file
- Pointer to struct
file
. unsigned int cmd
- Ioctl name.
unsigned long arg
- Ioctl argument.
int (*)(struct file *file, unsigned int cmd, void *arg) func
- function that will actually handle the ioctl
Description
Ancillary function that uses ioctl direction and size to copy from userspace. Then, it calls func, and, if needed, data is copied back to userspace.
-
dvb_attach
(FUNCTION, ARGS...)¶ attaches a DVB frontend into the DVB core.
Parameters
FUNCTION
- function on a frontend module to be called.
ARGS...
- FUNCTION arguments.
Description
This ancillary function loads a frontend module in runtime and runs
the FUNCTION function there, with ARGS.
As it increments symbol usage cont, at unregister, dvb_detach()
should be called.
-
dvb_detach
(FUNC)¶ detaches a DVB frontend loaded via
dvb_attach()
Parameters
FUNC
- attach function
Description
Decrements usage count for a function previously called via dvb_attach()
.
2.1.3. Digital TV Ring buffer¶
Those routines implement ring buffers used to handle digital TV data and copy it from/to userspace.
Note
- For performance reasons read and write routines don’t check buffer sizes and/or number of bytes free/available. This has to be done before these routines are called. For example:
/* write @buflen: bytes */ free = dvb_ringbuffer_free(rbuf); if (free >= buflen) count = dvb_ringbuffer_write(rbuf, buffer, buflen); else /* do something */ /* read min. 1000, max. @bufsize: bytes */ avail = dvb_ringbuffer_avail(rbuf); if (avail >= 1000) count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize)); else /* do something */
- If there is exactly one reader and one writer, there is no need to lock read or write operations. Two or more readers must be locked against each other. Flushing the buffer counts as a read operation. Resetting the buffer counts as a read and write operation. Two or more writers must be locked against each other.
-
struct
dvb_ringbuffer
¶ Describes a ring buffer used at DVB framework
Definition
struct dvb_ringbuffer {
u8 * data;
ssize_t size;
ssize_t pread;
ssize_t pwrite;
int error;
wait_queue_head_t queue;
spinlock_t lock;
};
Members
data
- Area were the ringbuffer data is written
size
- size of the ringbuffer
pread
- next position to read
pwrite
- next position to write
error
- used by ringbuffer clients to indicate that an error happened.
queue
- Wait queue used by ringbuffer clients to indicate when buffer was filled
lock
- Spinlock used to protect the ringbuffer
-
void
dvb_ringbuffer_init
(struct dvb_ringbuffer * rbuf, void * data, size_t len)¶ initialize ring buffer, lock and queue
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
void * data
- pointer to the buffer where the data will be stored
size_t len
- bytes from ring buffer into buf
-
int
dvb_ringbuffer_empty
(struct dvb_ringbuffer * rbuf)¶ test whether buffer is empty
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
-
ssize_t
dvb_ringbuffer_free
(struct dvb_ringbuffer * rbuf)¶ returns the number of free bytes in the buffer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
Return
number of free bytes in the buffer
-
ssize_t
dvb_ringbuffer_avail
(struct dvb_ringbuffer * rbuf)¶ returns the number of bytes waiting in the buffer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
Return
number of bytes waiting in the buffer
-
void
dvb_ringbuffer_reset
(struct dvb_ringbuffer * rbuf)¶ resets the ringbuffer to initial state
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
Description
Resets the read and write pointers to zero and flush the buffer.
This counts as a read and write operation
-
void
dvb_ringbuffer_flush
(struct dvb_ringbuffer * rbuf)¶ flush buffer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
-
void
dvb_ringbuffer_flush_spinlock_wakeup
(struct dvb_ringbuffer * rbuf)¶ flush buffer protected by spinlock and wake-up waiting task(s)
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
-
DVB_RINGBUFFER_PEEK
(rbuf, offs)¶ peek at byte offs in the buffer
Parameters
rbuf
- pointer to struct dvb_ringbuffer
offs
- offset inside the ringbuffer
-
DVB_RINGBUFFER_SKIP
(rbuf, num)¶ advance read ptr by num bytes
Parameters
rbuf
- pointer to struct dvb_ringbuffer
num
- number of bytes to advance
-
ssize_t
dvb_ringbuffer_read_user
(struct dvb_ringbuffer * rbuf, u8 __user * buf, size_t len)¶ Reads a buffer into a user pointer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
u8 __user * buf
- pointer to the buffer where the data will be stored
size_t len
- bytes from ring buffer into buf
Description
This variant assumes that the buffer is a memory at the userspace. So,
it will internally call copy_to_user()
.
Return
number of bytes transferred or -EFAULT
-
void
dvb_ringbuffer_read
(struct dvb_ringbuffer * rbuf, u8 * buf, size_t len)¶ Reads a buffer into a pointer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
u8 * buf
- pointer to the buffer where the data will be stored
size_t len
- bytes from ring buffer into buf
Description
This variant assumes that the buffer is a memory at the Kernel space
Return
number of bytes transferred or -EFAULT
-
DVB_RINGBUFFER_WRITE_BYTE
(rbuf, byte)¶ write single byte to ring buffer
Parameters
rbuf
- pointer to struct dvb_ringbuffer
byte
- byte to write
-
ssize_t
dvb_ringbuffer_write
(struct dvb_ringbuffer * rbuf, const u8 * buf, size_t len)¶ Writes a buffer into the ringbuffer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
const u8 * buf
- pointer to the buffer where the data will be read
size_t len
- bytes from ring buffer into buf
Description
This variant assumes that the buffer is a memory at the Kernel space
Return
number of bytes transferred or -EFAULT
-
ssize_t
dvb_ringbuffer_write_user
(struct dvb_ringbuffer * rbuf, const u8 __user * buf, size_t len)¶ Writes a buffer received via a user pointer
Parameters
struct dvb_ringbuffer * rbuf
- pointer to struct dvb_ringbuffer
const u8 __user * buf
- pointer to the buffer where the data will be read
size_t len
- bytes from ring buffer into buf
Description
This variant assumes that the buffer is a memory at the userspace. So,
it will internally call copy_from_user()
.
Return
number of bytes transferred or -EFAULT
-
ssize_t
dvb_ringbuffer_pkt_write
(struct dvb_ringbuffer * rbuf, u8 * buf, size_t len)¶ Write a packet into the ringbuffer.
Parameters
struct dvb_ringbuffer * rbuf
- Ringbuffer to write to.
u8 * buf
- Buffer to write.
size_t len
- Length of buffer (currently limited to 65535 bytes max).
Return
Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
-
ssize_t
dvb_ringbuffer_pkt_read_user
(struct dvb_ringbuffer * rbuf, size_t idx, int offset, u8 __user * buf, size_t len)¶ Read from a packet in the ringbuffer.
Parameters
struct dvb_ringbuffer * rbuf
- Ringbuffer concerned.
size_t idx
- Packet index as returned by
dvb_ringbuffer_pkt_next()
. int offset
- Offset into packet to read from.
u8 __user * buf
- Destination buffer for data.
size_t len
- Size of destination buffer.
Return
Number of bytes read, or -EFAULT.
Note
unlike dvb_ringbuffer_read()
, this does NOT update the read pointer
in the ringbuffer. You must use dvb_ringbuffer_pkt_dispose()
to mark a
packet as no longer required.
-
ssize_t
dvb_ringbuffer_pkt_read
(struct dvb_ringbuffer * rbuf, size_t idx, int offset, u8 * buf, size_t len)¶ Read from a packet in the ringbuffer.
Parameters
struct dvb_ringbuffer * rbuf
- Ringbuffer concerned.
size_t idx
- Packet index as returned by
dvb_ringbuffer_pkt_next()
. int offset
- Offset into packet to read from.
u8 * buf
- Destination buffer for data.
size_t len
- Size of destination buffer.
Note
unlike dvb_ringbuffer_read_user()
, this DOES update the read pointer
in the ringbuffer.
Return
Number of bytes read, or -EFAULT.
-
void
dvb_ringbuffer_pkt_dispose
(struct dvb_ringbuffer * rbuf, size_t idx)¶ Dispose of a packet in the ring buffer.
Parameters
struct dvb_ringbuffer * rbuf
- Ring buffer concerned.
size_t idx
- Packet index as returned by
dvb_ringbuffer_pkt_next()
.
-
ssize_t
dvb_ringbuffer_pkt_next
(struct dvb_ringbuffer * rbuf, size_t idx, size_t * pktlen)¶ Get the index of the next packet in a ringbuffer.
Parameters
struct dvb_ringbuffer * rbuf
- Ringbuffer concerned.
size_t idx
- Previous packet index, or -1 to return the first packet index.
size_t * pktlen
- On success, will be updated to contain the length of the packet in bytes. returns Packet index (if >=0), or -1 if no packets available.