Apparently all I had to do was set the type attribute on the uart_port structure to anything that isn't PORT_UNKNOWN. Here's a functional driver that takes a GPIO pin and creates a read-only serial TTY: https://github.com/tdfischer/gpio_serial/blob/master/gpiotty.c :) On Tuesday, June 24, 2014 21:27:46 Pranay Srivastava wrote: > Hi Torrie, > > On Tue, Jun 24, 2014 at 6:26 PM, Torrie Fischer > > <tdfischer@xxxxxxxxxxxxxx> wrote: > > Hi, Pranay. > > > > Thanks for having a look. > > > > On Tuesday, June 24, 2014 13:42:35 Pranay Srivastava wrote: > >> I looked at uart_register code, it seems there's no read callback so > >> that's why you are getting that -EIO. > > > > From what I understand, I'm supposed to set up the interrupts needed in > > the > > startup function which is called when the device is opened. This never > > happens though, as adding a printk results in no output. > > I think this might be causing it, if you see tty_open then it has a call to > , > > tty_open_current_tty , this seems to be the only one which I think is > not making the driver being looked up and hence no uport->open > > so in case there's an already a tty attached to current then i think > it isn't opening > a new one. Maybe you need to detach this tty? Not so sure I'll look > again what can be done. > > >> I think you can put this call in your start_tx since uart_start is > >> calling port->start_tx at the end so i guess you should be good there. > > > > I suspect that start_tx is not getting called since adding a printk in my > > start_tx function doesn't result in any output. > > > >> I don't have much idea how will you read from it though. > > > > I'm able to read from it by waiting for a rising edge interrupt and then > > bit- banging the GPIO line in userspace, though at a slow baud that is > > unusable. I need 9600 to read from my device :) > > Ok good!. I don't have much idea about GPIO. While searching I found > there's a GPIO library for Raspi. I don't know how much help that > would be but i > guess you don't want to use it.
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