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

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Date:   Wed, 16 Jun 2021 09:45:10 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>,
        赵振国 <zhenguo6858@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: n_gsm: Fix CR bit value when initiator=0

On 16. 06. 21, 9:39, Greg KH wrote:
> 
> A: http://en.wikipedia.org/wiki/Top_post
> Q: Were do I find info about this thing called top-posting?
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?
> A: Top-posting.
> Q: What is the most annoying thing in e-mail?
> 
> A: No.
> Q: Should I include quotations after my reply?
> 
> 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.

And why it was able to work until now. I.e. isn't the Documentation wrong?

thanks,
-- 
js
suse labs