Changes between Version 65 and Version 66 of Developer/Simulators/QEMU/CANEmulation

Timestamp:

09/12/13 13:03:04 (11 years ago)

Author:

Jinyang

Comment:

/* Step 3: Build a Basic PCI-CAN device in qemu */

Developer/Simulators/QEMU/CANEmulation

@@ -410 +410 @@
    { .name = "CAN",          .open = qemu_chr_open_can },
 The qemu_char_open_can() function is used to initialize the backend including analyzing the start options, allocating some memory, opening the SocketCAN device, setting the CAN filter etc.
+==  Add the start options  ==
+
+We should start the backend like "-chrdev can,id=sja1000,port=vcan0". The valid options for backend list in qemu_chardev_opts variable. The argument 'port' is part of them, so we can use it directly or you should add the option you want to the qemu_chardev_opts variable. When qemu started, you can get the value using qemu_opt_get() function.
 ==  Add writing routine  ==
 
@@ -429 +432 @@
 ==  Add reading routine  ==
 
-
-
-
+The reading routine is a little complicate than the writing routine. Because we don't known when we should the CAN message, so we should check the file discriptor all the time. I will simply explain how this works.
+
+QEMU use IOhandlder thread to deal with this kind of operation. The main_loop_wait() function in main-loop.c will be always be executed. This actually called main_loop_wait()-main-loop.c => os_host_main_loop_wait()-main-loop.c => select(), which means the system call select() will be called all the time.