On Tuesday 15 April 2008 15:40, Anton Vorontsov wrote: > On Tue, Apr 15, 2008 at 03:22:33PM +0200, Laurent Pinchart wrote: > > Hi everybody, > > > > I'm implementing flow control and modem control lines support in the > > cpm_uart driver. > > > > The implementation is based on the GPIO lib. Modem control lines are > > described in the device tree as GPIO resources and accessed through the OF > > GPIO bindings. The I/O ports have to be initialized as GPIOs in the > > platform-specific code. > > > > Reading and writing the modem control lines isn't an issue, but activating > > hardware flow control is more complex. The driver needs to turn dedicated > > functions on and off for the RTS and CTS signals, and the GPIO API doesn't > > provide a way to access the PPAR* registers (which does make sense - > > although arguably - as PPAR* control specific functions, not GPIOs). > > > > Hardcoding RTS and CTS lines control in the driver is not an option I want > > to consider. Extending the GPIO API to handled special functions has been > > nacked in the past (see > > http://ozlabs.org/pipermail/linuxppc-dev/2008-February/051241.html). An > > option would be to export gpio_to_chip from drivers/gpio/gpiolib.c and use > > cpm1/2_set_pin in the cpm_uart driver. > > Since you have successfuly ported QE USB controller onto CPM USB > hardware, now it's obvious that we will need generic gpio_set_dedicated() > function. So I would rather beg David to accept gpio_set_dedicated() > approach instead of exporting gpio_to_chip(). That way we'll kill two > birds with one stone.
Or maybe some kind of gpio_set_option() with flags specific to the controller ? This could be used to enable open-drain outputs or internal pull-ups for instance. -- Laurent Pinchart CSE Semaphore Belgium Chaussee de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 F +32 (2) 387 42 75
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