Re: [ECOS] Config keys

[Jonathan Larmour <jifl at eCosCentric dot com>]

David Marqvar (DAM) wrote:
> Hi,
>
> Is there any good reason that the config keys for serial devices are
> serial-specific, e.g.:
>
> #define CYG_IO_GET_CONFIG_SERIAL_INPUT_FLUSH           0x0104
>
> could be defined as:
>
> #define CYG_IO_GET_CONFIG_SERIAL_INPUT_FLUSH
> CYG_IO_GET_CONFIG_INPUT_FLUSH
>
> and the generic part should then be expanded with
> // ======== 0x1000 Generic
> ===================================================
> // Get/Set configuration 'key' values that can apply to more than one
> // class of device.
> #define CYG_IO_GET_CONFIG_INPUT_FLUSH           0x1104
>
> ... and so on.
>
> This would allow different serial-alike devices to be handled in a common
> way by upper layer applications.
>
> In our development we both have serial devices as UART and USB (acting as a
> serial device). Others may come, for example serial Bluetooth...
>
> I can file a patch.... :-)

A patch always helps :-). I'd be sympathetic, although fairly obviously 
this is part of the API so the existing macro name needs to be kept as well.

But there's still an issue since not everything is right with this 
anyway... why should something associated with getting a config do an 
input flush, or really do _anything_? "Getting" something should be a 
passive operation and not change the system. Well, we can't change the 
serial drivers easily now, but we should get it right for any new extensions.

Arguably there is a need for some other function (dare I mention the dread 
name "ioctl"?) which deals with other driver-specific operations.

But since I don't like the thought of an extra function pointer, I'd 
probably just go with something like CYG_IO_SET_CONFIG_INPUT_FLUSH and add 
something in the serial_set_config to chain to serial_get_config for this 
particular value.

(Plus of course there's no easy way for new packages to extend the config 
keys but there's no point worrying about that until eCos v3.0 ;-).)

Jifl
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