pvrusb2.rst (9493B)
1.. SPDX-License-Identifier: GPL-2.0 2 3The pvrusb2 driver 4================== 5 6Author: Mike Isely <isely@pobox.com> 7 8Background 9---------- 10 11This driver is intended for the "Hauppauge WinTV PVR USB 2.0", which 12is a USB 2.0 hosted TV Tuner. This driver is a work in progress. 13Its history started with the reverse-engineering effort by Björn 14Danielsson <pvrusb2@dax.nu> whose web page can be found here: 15http://pvrusb2.dax.nu/ 16 17From there Aurelien Alleaume <slts@free.fr> began an effort to 18create a video4linux compatible driver. I began with Aurelien's 19last known snapshot and evolved the driver to the state it is in 20here. 21 22More information on this driver can be found at: 23https://www.isely.net/pvrusb2.html 24 25 26This driver has a strong separation of layers. They are very 27roughly: 28 291. Low level wire-protocol implementation with the device. 30 312. I2C adaptor implementation and corresponding I2C client drivers 32 implemented elsewhere in V4L. 33 343. High level hardware driver implementation which coordinates all 35 activities that ensure correct operation of the device. 36 374. A "context" layer which manages instancing of driver, setup, 38 tear-down, arbitration, and interaction with high level 39 interfaces appropriately as devices are hotplugged in the 40 system. 41 425. High level interfaces which glue the driver to various published 43 Linux APIs (V4L, sysfs, maybe DVB in the future). 44 45The most important shearing layer is between the top 2 layers. A 46lot of work went into the driver to ensure that any kind of 47conceivable API can be laid on top of the core driver. (Yes, the 48driver internally leverages V4L to do its work but that really has 49nothing to do with the API published by the driver to the outside 50world.) The architecture allows for different APIs to 51simultaneously access the driver. I have a strong sense of fairness 52about APIs and also feel that it is a good design principle to keep 53implementation and interface isolated from each other. Thus while 54right now the V4L high level interface is the most complete, the 55sysfs high level interface will work equally well for similar 56functions, and there's no reason I see right now why it shouldn't be 57possible to produce a DVB high level interface that can sit right 58alongside V4L. 59 60Building 61-------- 62 63To build these modules essentially amounts to just running "Make", 64but you need the kernel source tree nearby and you will likely also 65want to set a few controlling environment variables first in order 66to link things up with that source tree. Please see the Makefile 67here for comments that explain how to do that. 68 69Source file list / functional overview 70-------------------------------------- 71 72(Note: The term "module" used below generally refers to loosely 73defined functional units within the pvrusb2 driver and bears no 74relation to the Linux kernel's concept of a loadable module.) 75 76pvrusb2-audio.[ch] - This is glue logic that resides between this 77 driver and the msp3400.ko I2C client driver (which is found 78 elsewhere in V4L). 79 80pvrusb2-context.[ch] - This module implements the context for an 81 instance of the driver. Everything else eventually ties back to 82 or is otherwise instanced within the data structures implemented 83 here. Hotplugging is ultimately coordinated here. All high level 84 interfaces tie into the driver through this module. This module 85 helps arbitrate each interface's access to the actual driver core, 86 and is designed to allow concurrent access through multiple 87 instances of multiple interfaces (thus you can for example change 88 the tuner's frequency through sysfs while simultaneously streaming 89 video through V4L out to an instance of mplayer). 90 91pvrusb2-debug.h - This header defines a printk() wrapper and a mask 92 of debugging bit definitions for the various kinds of debug 93 messages that can be enabled within the driver. 94 95pvrusb2-debugifc.[ch] - This module implements a crude command line 96 oriented debug interface into the driver. Aside from being part 97 of the process for implementing manual firmware extraction (see 98 the pvrusb2 web site mentioned earlier), probably I'm the only one 99 who has ever used this. It is mainly a debugging aid. 100 101pvrusb2-eeprom.[ch] - This is glue logic that resides between this 102 driver the tveeprom.ko module, which is itself implemented 103 elsewhere in V4L. 104 105pvrusb2-encoder.[ch] - This module implements all protocol needed to 106 interact with the Conexant mpeg2 encoder chip within the pvrusb2 107 device. It is a crude echo of corresponding logic in ivtv, 108 however the design goals (strict isolation) and physical layer 109 (proxy through USB instead of PCI) are enough different that this 110 implementation had to be completely different. 111 112pvrusb2-hdw-internal.h - This header defines the core data structure 113 in the driver used to track ALL internal state related to control 114 of the hardware. Nobody outside of the core hardware-handling 115 modules should have any business using this header. All external 116 access to the driver should be through one of the high level 117 interfaces (e.g. V4L, sysfs, etc), and in fact even those high 118 level interfaces are restricted to the API defined in 119 pvrusb2-hdw.h and NOT this header. 120 121pvrusb2-hdw.h - This header defines the full internal API for 122 controlling the hardware. High level interfaces (e.g. V4L, sysfs) 123 will work through here. 124 125pvrusb2-hdw.c - This module implements all the various bits of logic 126 that handle overall control of a specific pvrusb2 device. 127 (Policy, instantiation, and arbitration of pvrusb2 devices fall 128 within the jurisdiction of pvrusb-context not here). 129 130pvrusb2-i2c-chips-\*.c - These modules implement the glue logic to 131 tie together and configure various I2C modules as they attach to 132 the I2C bus. There are two versions of this file. The "v4l2" 133 version is intended to be used in-tree alongside V4L, where we 134 implement just the logic that makes sense for a pure V4L 135 environment. The "all" version is intended for use outside of 136 V4L, where we might encounter other possibly "challenging" modules 137 from ivtv or older kernel snapshots (or even the support modules 138 in the standalone snapshot). 139 140pvrusb2-i2c-cmd-v4l1.[ch] - This module implements generic V4L1 141 compatible commands to the I2C modules. It is here where state 142 changes inside the pvrusb2 driver are translated into V4L1 143 commands that are in turn send to the various I2C modules. 144 145pvrusb2-i2c-cmd-v4l2.[ch] - This module implements generic V4L2 146 compatible commands to the I2C modules. It is here where state 147 changes inside the pvrusb2 driver are translated into V4L2 148 commands that are in turn send to the various I2C modules. 149 150pvrusb2-i2c-core.[ch] - This module provides an implementation of a 151 kernel-friendly I2C adaptor driver, through which other external 152 I2C client drivers (e.g. msp3400, tuner, lirc) may connect and 153 operate corresponding chips within the pvrusb2 device. It is 154 through here that other V4L modules can reach into this driver to 155 operate specific pieces (and those modules are in turn driven by 156 glue logic which is coordinated by pvrusb2-hdw, doled out by 157 pvrusb2-context, and then ultimately made available to users 158 through one of the high level interfaces). 159 160pvrusb2-io.[ch] - This module implements a very low level ring of 161 transfer buffers, required in order to stream data from the 162 device. This module is *very* low level. It only operates the 163 buffers and makes no attempt to define any policy or mechanism for 164 how such buffers might be used. 165 166pvrusb2-ioread.[ch] - This module layers on top of pvrusb2-io.[ch] 167 to provide a streaming API usable by a read() system call style of 168 I/O. Right now this is the only layer on top of pvrusb2-io.[ch], 169 however the underlying architecture here was intended to allow for 170 other styles of I/O to be implemented with additional modules, like 171 mmap()'ed buffers or something even more exotic. 172 173pvrusb2-main.c - This is the top level of the driver. Module level 174 and USB core entry points are here. This is our "main". 175 176pvrusb2-sysfs.[ch] - This is the high level interface which ties the 177 pvrusb2 driver into sysfs. Through this interface you can do 178 everything with the driver except actually stream data. 179 180pvrusb2-tuner.[ch] - This is glue logic that resides between this 181 driver and the tuner.ko I2C client driver (which is found 182 elsewhere in V4L). 183 184pvrusb2-util.h - This header defines some common macros used 185 throughout the driver. These macros are not really specific to 186 the driver, but they had to go somewhere. 187 188pvrusb2-v4l2.[ch] - This is the high level interface which ties the 189 pvrusb2 driver into video4linux. It is through here that V4L 190 applications can open and operate the driver in the usual V4L 191 ways. Note that **ALL** V4L functionality is published only 192 through here and nowhere else. 193 194pvrusb2-video-\*.[ch] - This is glue logic that resides between this 195 driver and the saa711x.ko I2C client driver (which is found 196 elsewhere in V4L). Note that saa711x.ko used to be known as 197 saa7115.ko in ivtv. There are two versions of this; one is 198 selected depending on the particular saa711[5x].ko that is found. 199 200pvrusb2.h - This header contains compile time tunable parameters 201 (and at the moment the driver has very little that needs to be 202 tuned).