1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
|
\input{configpres}
\title{Character Device Driver Interaction}
\maketitle
\subsection{Character Devices}
\begin{frame}
\frametitle{Syscall Interface}
\begin{center}
\includegraphics[width=5cm]{images/syscall.png}
\end{center}
\end{frame}
\begin{frame}
\frametitle{Character Device Driver Interaction}
\begin{itemize}
\item open
\item release
\item read
\item write
\item fsync
\item llseek
\item poll
\item mmap
\item ioctl
\item \dots
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{open}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
int (*open) (struct inode *, struct file *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [open:] The first operation on a character device. The function implementation is optional. If not implemented, it will always succeed and the driver is not informed of the open.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/open.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{release}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
int (*release) (struct inode *, struct file *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [release:] The last operation on a character device. The function implementation is optional. If not implemented, it will always succeed and the driver is not informed of the release.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/release.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{read}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [read:] Read data from the character device. The data is copied to userspace using the \emph{copy\_to\_user} function.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/read.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{write}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [write:] Write data to the character device. The data is copied from usersapce using the \emph{copy\_from\_user} function.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/write.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{fsync}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
int (*fsync) (struct file *, struct dentry *, int datasync);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [fsync:] Flush all cached data to the device.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/fsync.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{llseek}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
loff_t (*llseek) (struct file *, loff_t, int);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [llseek:] Set the current position for read and write access.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/llseek.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{poll}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
unsigned int (*poll) (struct file *, struct poll_table_struct *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [poll:] Implements poll, epoll, and select functionality. If it is not implemented, blocking I/O is not possible.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/poll.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{mmap}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
int (*mmap) (struct file *, struct vm_area_struct *);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [mmap:] Creates a mapping of the device memory for the userspace process context.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/mmap.png}
\end{center}
\end{frame}
\begin{frame}[fragile]
\frametitle{ioctl}
\begin{itemize}
\item Prototype
\begin{tiny}
\begin{lstlisting}[frame=trBL]
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
\end{lstlisting}
\end{tiny}
\item Description
\begin{description}
\item [ioctl:] Implements device-specific commands. This should be avoided since better, standard interfaces for most cases already exist.
\end{description}
\item Data Flow
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{images/ioctl.png}
\end{center}
\end{frame}
\input{tailpres}
|
