Add qemu 2.4.0

[kvmfornfv.git] / qemu / roms / SLOF / lib / libc / README.txt

diff --git a/qemu/roms/SLOF/lib/libc/README.txt b/qemu/roms/SLOF/lib/libc/README.txt
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+
+ Standard C library for the SLOF firmware project
+ ================================================
+
+To use this library, link your target against the "libc.a" archive.
+
+However, there are some prerequisites before you can use certain parts of the
+library:
+
+1) If you want to use malloc() and the like, you have to supply an implemen-
+   tation of sbrk() in your own code. malloc() uses sbrk() to get new, free
+   memory regions.
+   
+   Prototype:   void *sbrk(int incr);
+   Description: sbrk() increments the available data space by incr bytes and
+                returns a pointer to the start of the new area.
+   
+   See the man-page of sbrk for details about this function.
+
+2) Before you can use the stdio output functions like printf(), puts() and the
+   like, you have to provide a standard write() function in your code.
+   printf() and the like use write() to print out the strings to the standard
+   output.
+
+   Prototype:   ssize_t write(int fd, const void *buf, size_t cnt);
+   Description: Write cnt byte from the buffer buf to the stream associated
+                with the file descriptor fd.
+
+   The stdio functions will print their output to the stdout channel which is
+   assigned with the file descriptor 1 by default. Note that the stdio
+   functions will not use open() before calling write(), so if the stdout
+   cannel needs to be opened first, you should do that in your start-up code
+   before using the libc functions for the first time.
+   
+3) Before you can use the stdio input functions like scanf() and the
+   like, you have to provide a standard read() function in your code.
+   scanf() and the like use read() to get the characters from the standard
+   input.
+
+   Prototype:   ssize_t read(int fd, void *buf, size_t cnt);
+   Description: Read cnt byte from the stream associated with the file
+                descriptor fd and put them into the buffer buf.
+
+   The stdio functions will get their input from the stdin channel which is
+   assigned with the file descriptor 0 by default. Note that the stdio
+   functions will not use open() before calling read(), so if the stdin
+   cannel needs to be opened first, you should do that in your start-up code
+   before using the libc functions for the first time.
+