On Fri, 21 Aug 2009, Alan Cox wrote: > > Alan, related to this problem is the fact that usb_serial_driver > > doesn't include a "hangup" method. I'm not sure that making > > serial_hangup() call serial_do_down() is correct, but if it is then > > shouldn't we call port->serial->type->open() afterwards? Otherwise the > > lower driver can't know that the port is still open. > > After a hangup the port isn't open (at the physical level anyway). It may > be re-opened by another open() call later Or, oddly enough, another open() call earlier... > but the original user lost > access to it and shouldn't touch the h/w post hangup completion. Then surely serial_open() should call serial->type->open() _after_ tty_port_block_til_ready(), not before. > > Furthermore, shouldn't we check ASYNCB_INITIALIZED in serial_close()? > > Possibly - I was in the middle of debugging the newest bits when Linus > annoyed me. Certainly there are issues in the current code if you get > a hangup while waiting for open to complete. I fixed that in the patches > I sent Greg but didn't finish debugging it. Well, yes. The way it is now, you get: serial_open() /* first user */ serial->type->open() /* initializes the hardware */ tty_port_block_til_ready() /* returns immediately */ serial_open() /* second user */ serial->type->open skipped because the port is already open tty_port_block_til_ready() /* blocks */ serial_hangup() /* first connection drops */ serial_do_down() serial->type-close() /* resets the hardware */ ... tty_port_block_til_ready() returns Now the second user tries to do stuff but the hardware isn't ready. Instead this should go: serial_open() /* first user */ tty_port_block_til_ready() /* returns immediately */ serial->type->open() /* initializes the hardware */ serial_open() /* second user */ tty_port_block_til_ready() /* blocks */ serial_hangup() /* first connection drops */ serial_do_down() serial->type-close() /* resets the hardware */ ... tty_port_block_til_ready() returns serial->type->open() /* not skipped */ Now the second user can proceed to use the hardware. Or have I misunderstood how this is intended to work? Alan Stern P.S.: Can you explain the reason why tty_port and tty_struct are two separate structures? Isn't the same port always associated with the same tty? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
