Re: [PATCH] tty: n_gsm: Fix CR bit value when initiator=0

[Greg KH]

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http://daringfireball.net/2007/07/on_top

On Wed, Jun 16, 2021 at 03:29:11PM +0800, 赵振国 wrote:
> Dear gregkh
> 
> 1:  Documentation/driver-api/serial/n_gsm.rst
> 
> The text introduces the config of master ( c.initiator = 1), but the
> config of as responder is different.
> when set gsm->initiator=0 by GSMIOC_SETCONF ,ngsm driver should be
> responder(slaver)
> 
> config：
> 	c.initiator = 0;    // set initiator=0，ngsm as responder
> 	ioctl(fd, GSMIOC_SETCONF, &c);
> 
> 2:  if master side send SABM/DISC frame data by uart dev
>     DLC0 control data frame:f9 03 3f 01 1c f9
>     kernel log： gsmld_receive: 00000000: f9 03 3f 01 1c f9
> 
> {
> 	cr = gsm->address & 1;		/* C/R bit */
> //CR value=1
> 
> 	gsm_print_packet("<--", address, cr, gsm->control, gsm->buf, gsm->len);
> 
> 	cr ^= 1 - gsm->initiator;	/* Flip so 1 always means command */
> //when gsm->initiator is 0, CR value=0 by "^=" calculation
> 	dlci = gsm->dlci[address];
> 
> 	switch (gsm->control) {
> 	case SABM|PF:
> 		if (cr == 0)
> 			goto invalid;                       //if CR value=0,ngsm will goto
> invalid,but the dlc0 control frame data is right,if we can't modify
> ,ngsm can't send UA response data
> }

I am sorry, but I really do not understand what you are saying here.
Please resubmit your patch with an updated changelog that explains why
this change is needed and what it does.

thanks,

greg k-h