Re: [RFC] gatchat: implement timeout setting for commands

[Denis Kenzior <denkenz@gmail.com>]

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Hi Martin,

On 9/2/19 4:10 PM, Martin Hundebøll wrote:
> The adds a function to the set a chat-wide timeout for at commands. It
> allows plugins to handle cases where the modem fails to respond with
> either an OK or an error.

Okay, this is sort of a known problem without a really good solution...

> 
> Without these timeouts, the plugin is never notified about a hanging
> command, and it has no way to detect it; effectively leaving the device
> in a broken state, where only a full restart of the ofono service
> unbreaks it.

The trouble is, what if this happens on a command handled by a generic 
atmodem driver atom?  Are you going in and adding timeout handling to 
all command callbacks?

If this timeout only happens in special cases, then those can be taken 
care of by setting up your own timeout...

> 
> If a timeout occurs, the passed callback is invoked with 'ok' set to
> false, and no final response in the result. This allows callbacks to
> identify the timeout with this snippet:
> 
>    if (!ok) {
>      decode_at_error(&error, g_at_result_final_response(result));
>      if (error.type == OFONO_ERROR_TYPE_FAILURE) {
>        /* handle timeout */
>      }
>    }

About the only thing I can suggest is to create a separate timeout 
callback for the GAtChat object that the modem driver can set.  That way 
if the timeout happens, the modem driver can just reset the entire 
setup.  E.g. maybe via ofono_modem_reset.

> ---
>   gatchat/gatchat.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++
>   gatchat/gatchat.h |  9 +++++++
>   plugins/quectel.c |  3 ---

Also, I guess this part was extraneous :)

>   3 files changed, 69 insertions(+), 3 deletions(-)
> 

Regards,
-Denis