On 3/27/06, Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> wrote: > > 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. > Thanks Glynn, that explains a lot! > -- > 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
