203 lines
9.3 KiB
ReStructuredText
203 lines
9.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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The pvrusb2 driver
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==================
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Author: Mike Isely <isely@pobox.com>
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Background
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----------
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This driver is intended for the "Hauppauge WinTV PVR USB 2.0", which
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is a USB 2.0 hosted TV Tuner. This driver is a work in progress.
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Its history started with the reverse-engineering effort by Björn
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Danielsson <pvrusb2@dax.nu> whose web page can be found here:
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http://pvrusb2.dax.nu/
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From there Aurelien Alleaume <slts@free.fr> began an effort to
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create a video4linux compatible driver. I began with Aurelien's
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last known snapshot and evolved the driver to the state it is in
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here.
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More information on this driver can be found at:
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https://www.isely.net/pvrusb2.html
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This driver has a strong separation of layers. They are very
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roughly:
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1. Low level wire-protocol implementation with the device.
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2. I2C adaptor implementation and corresponding I2C client drivers
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implemented elsewhere in V4L.
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3. High level hardware driver implementation which coordinates all
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activities that ensure correct operation of the device.
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4. A "context" layer which manages instancing of driver, setup,
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tear-down, arbitration, and interaction with high level
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interfaces appropriately as devices are hotplugged in the
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system.
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5. High level interfaces which glue the driver to various published
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Linux APIs (V4L, sysfs, maybe DVB in the future).
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The most important shearing layer is between the top 2 layers. A
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lot of work went into the driver to ensure that any kind of
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conceivable API can be laid on top of the core driver. (Yes, the
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driver internally leverages V4L to do its work but that really has
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nothing to do with the API published by the driver to the outside
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world.) The architecture allows for different APIs to
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simultaneously access the driver. I have a strong sense of fairness
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about APIs and also feel that it is a good design principle to keep
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implementation and interface isolated from each other. Thus while
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right now the V4L high level interface is the most complete, the
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sysfs high level interface will work equally well for similar
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functions, and there's no reason I see right now why it shouldn't be
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possible to produce a DVB high level interface that can sit right
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alongside V4L.
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Building
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--------
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To build these modules essentially amounts to just running "Make",
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but you need the kernel source tree nearby and you will likely also
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want to set a few controlling environment variables first in order
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to link things up with that source tree. Please see the Makefile
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here for comments that explain how to do that.
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Source file list / functional overview
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--------------------------------------
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(Note: The term "module" used below generally refers to loosely
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defined functional units within the pvrusb2 driver and bears no
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relation to the Linux kernel's concept of a loadable module.)
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pvrusb2-audio.[ch] - This is glue logic that resides between this
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driver and the msp3400.ko I2C client driver (which is found
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elsewhere in V4L).
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pvrusb2-context.[ch] - This module implements the context for an
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instance of the driver. Everything else eventually ties back to
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or is otherwise instanced within the data structures implemented
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here. Hotplugging is ultimately coordinated here. All high level
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interfaces tie into the driver through this module. This module
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helps arbitrate each interface's access to the actual driver core,
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and is designed to allow concurrent access through multiple
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instances of multiple interfaces (thus you can for example change
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the tuner's frequency through sysfs while simultaneously streaming
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video through V4L out to an instance of mplayer).
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pvrusb2-debug.h - This header defines a printk() wrapper and a mask
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of debugging bit definitions for the various kinds of debug
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messages that can be enabled within the driver.
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pvrusb2-debugifc.[ch] - This module implements a crude command line
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oriented debug interface into the driver. Aside from being part
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of the process for implementing manual firmware extraction (see
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the pvrusb2 web site mentioned earlier), probably I'm the only one
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who has ever used this. It is mainly a debugging aid.
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pvrusb2-eeprom.[ch] - This is glue logic that resides between this
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driver the tveeprom.ko module, which is itself implemented
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elsewhere in V4L.
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pvrusb2-encoder.[ch] - This module implements all protocol needed to
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interact with the Conexant mpeg2 encoder chip within the pvrusb2
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device. It is a crude echo of corresponding logic in ivtv,
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however the design goals (strict isolation) and physical layer
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(proxy through USB instead of PCI) are enough different that this
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implementation had to be completely different.
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pvrusb2-hdw-internal.h - This header defines the core data structure
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in the driver used to track ALL internal state related to control
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of the hardware. Nobody outside of the core hardware-handling
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modules should have any business using this header. All external
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access to the driver should be through one of the high level
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interfaces (e.g. V4L, sysfs, etc), and in fact even those high
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level interfaces are restricted to the API defined in
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pvrusb2-hdw.h and NOT this header.
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pvrusb2-hdw.h - This header defines the full internal API for
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controlling the hardware. High level interfaces (e.g. V4L, sysfs)
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will work through here.
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pvrusb2-hdw.c - This module implements all the various bits of logic
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that handle overall control of a specific pvrusb2 device.
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(Policy, instantiation, and arbitration of pvrusb2 devices fall
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within the jurisdiction of pvrusb-context not here).
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pvrusb2-i2c-chips-\*.c - These modules implement the glue logic to
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tie together and configure various I2C modules as they attach to
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the I2C bus. There are two versions of this file. The "v4l2"
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version is intended to be used in-tree alongside V4L, where we
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implement just the logic that makes sense for a pure V4L
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environment. The "all" version is intended for use outside of
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V4L, where we might encounter other possibly "challenging" modules
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from ivtv or older kernel snapshots (or even the support modules
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in the standalone snapshot).
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pvrusb2-i2c-cmd-v4l1.[ch] - This module implements generic V4L1
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compatible commands to the I2C modules. It is here where state
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changes inside the pvrusb2 driver are translated into V4L1
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commands that are in turn send to the various I2C modules.
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pvrusb2-i2c-cmd-v4l2.[ch] - This module implements generic V4L2
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compatible commands to the I2C modules. It is here where state
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changes inside the pvrusb2 driver are translated into V4L2
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commands that are in turn send to the various I2C modules.
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pvrusb2-i2c-core.[ch] - This module provides an implementation of a
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kernel-friendly I2C adaptor driver, through which other external
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I2C client drivers (e.g. msp3400, tuner, lirc) may connect and
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operate corresponding chips within the pvrusb2 device. It is
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through here that other V4L modules can reach into this driver to
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operate specific pieces (and those modules are in turn driven by
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glue logic which is coordinated by pvrusb2-hdw, doled out by
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pvrusb2-context, and then ultimately made available to users
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through one of the high level interfaces).
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pvrusb2-io.[ch] - This module implements a very low level ring of
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transfer buffers, required in order to stream data from the
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device. This module is *very* low level. It only operates the
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buffers and makes no attempt to define any policy or mechanism for
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how such buffers might be used.
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pvrusb2-ioread.[ch] - This module layers on top of pvrusb2-io.[ch]
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to provide a streaming API usable by a read() system call style of
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I/O. Right now this is the only layer on top of pvrusb2-io.[ch],
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however the underlying architecture here was intended to allow for
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other styles of I/O to be implemented with additional modules, like
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mmap()'ed buffers or something even more exotic.
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pvrusb2-main.c - This is the top level of the driver. Module level
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and USB core entry points are here. This is our "main".
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pvrusb2-sysfs.[ch] - This is the high level interface which ties the
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pvrusb2 driver into sysfs. Through this interface you can do
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everything with the driver except actually stream data.
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pvrusb2-tuner.[ch] - This is glue logic that resides between this
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driver and the tuner.ko I2C client driver (which is found
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elsewhere in V4L).
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pvrusb2-util.h - This header defines some common macros used
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throughout the driver. These macros are not really specific to
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the driver, but they had to go somewhere.
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pvrusb2-v4l2.[ch] - This is the high level interface which ties the
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pvrusb2 driver into video4linux. It is through here that V4L
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applications can open and operate the driver in the usual V4L
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ways. Note that **ALL** V4L functionality is published only
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through here and nowhere else.
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pvrusb2-video-\*.[ch] - This is glue logic that resides between this
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driver and the saa711x.ko I2C client driver (which is found
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elsewhere in V4L). Note that saa711x.ko used to be known as
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saa7115.ko in ivtv. There are two versions of this; one is
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selected depending on the particular saa711[5x].ko that is found.
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pvrusb2.h - This header contains compile time tunable parameters
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(and at the moment the driver has very little that needs to be
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tuned).
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