On Mon, Mar 4, 2019 at 6:53 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, Mar 04, 2019 at 05:46:54PM +0530, Subhashini Rao Beerisetty wrote: > > Hi All, > > > > > > I’ve an UART ports on Xilinx FPGA board and it gets connected to PC > > via PCIe bus. I could not find any kernel serial driver which supports > > our hardware so I plan to develop a new driver. I see two approaches > > to develop an UART driver i.e. either by using tty_register_driver() > > or an uart_register_driver(). > > > > > > Regarding my UART module, it has a counter of 16 bits and runs on a > > 32Mhz clock. It supports all the standard & non-standard baud’s up to > > 4Mbps. > > What type of UART is it? Odds are it is based on an existing design, no > one creates a brand-new UART anymore. Hopefully. If not, what a > waste... For UART type, I see the permitted types are none, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. Looking into the data sheet I haven’t found any register or parameter defining any of those UART types. Is ‘UART type’ is determined from a register settings point of view or a pinout point of view? > > > If I used struct tty_operations, I noticed that baud rate changing is > > done via “.set_termios” API, but this method only supports standard > > baud rates. I’d like to know why this API does not support > > non-standard baud rates? > > Why do you think it does not? >From data sheet point of view I'm clear on how to set the non-standard baud rate, even I exposed a custom Ioctl for this. But here I’m trying to understand how it is achieved by using available UART kernel framework. For non-standard baud rate requests, observed that tty->termios.c_ispeed & tty->termios.c_ospeed set to 38400. I did not understood why it changes? > > Anyway, use the uart interface as odds are your uart is already > supported. Get the data sheet and start reading :) > > good luck, > > greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
