Holy Aavu wrote: > > My machine has only one serial port. Now I want to add more *software* > > (virtual) serial ports. I also want to make a virtual serial cable > > between a real serial port and a virtual one OR between virtual ports. > > Is there any way to solve that problem in our universe? > > I have a doubt... I am not sure if you can have a full working > solution to make all programs run using the virtual serial ports. > Because, there *might* be some programs which actually use the 'in' > and 'out' instructions of the processor directly from a user space > program. (After calling iopl/ioperm etc to elevate their I/O > privileges to directly use the IO ports) I dont think even a kernel > change can help in that case... > > Is my understanding correct or am I missing something? 1. Any such programs will only work with "PC-style" serial ports (8250 and compatible UARTs); they won't work with other serial hardware (e.g. multi-port serial cards). Also, such programs would require root privilege. Consequently, most programs which use serial ports limit themselves to using the /dev/tty* devices and their associated ioctl() calls. 2. You could change the iopl() system call so that it doesn't affect the IOPL bits in the EFLAGS register. Instead, you would handle the resulting exceptions, trapping attempts to access the UARTs and redirecting them to the "virtual UART" driver. The ioperm() system call would need similar modifications. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - : send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
