Re: [PATCH 2/4] bas_gigaset: collapse CR/LF at end of AT response

On Tue, Feb 23, 2010 at 02:19:19PM +0100, Tilman Schmidt wrote:
> Simon Horman schrieb:
> > I am confused about what the value of MAX_RESP_SIZE means.
> > Is it a hw restriction?
> 
> It's an arbitrary limitation in the driver. The hardware specification
> says nothing about the possible length of AT responses from the device,
> so we had to draw a line somewhere. 512 bytes have so far proved to be
> amply sufficient.
> 
> In practice, the limit is only hit with the M10x devices (which transmit
> commands and data over the same channel) when the state machine gets out
> of sync and tries to interpret received payload data as AT responses.

Ok, understood. Thanks for the clarification.

> > It seems that up to MAX_RESP_SIZE of string-data is permitted if the line
> > is terminated by CR. But only MAX_RESP_SIZE -1  bytes if the line is
> > terminated by LF or CR LF.
> 
> Note that when storing the CR in cs->respdata[0] for possible collapsing
> with a subsequent LF, the cbytes counter is left at 0, so the CR gets
> overwritten by the first character of the next response if there's no
> intervening LF.

Yes, I had to look at that for quite a while :-)